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Diffstat (limited to 'fs/namei.c')
| -rw-r--r-- | fs/namei.c | 6581 |
1 files changed, 6581 insertions, 0 deletions
diff --git a/fs/namei.c b/fs/namei.c new file mode 100644 index 000000000..20a6534ea --- /dev/null +++ b/fs/namei.c @@ -0,0 +1,6581 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * linux/fs/namei.c + * + * Copyright (C) 1991, 1992 Linus Torvalds + */ + +/* + * Some corrections by tytso. + */ + +/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname + * lookup logic. + */ +/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture. + */ + +#include <linux/init.h> +#include <linux/export.h> +#include <linux/slab.h> +#include <linux/wordpart.h> +#include <linux/fs.h> +#include <linux/filelock.h> +#include <linux/namei.h> +#include <linux/pagemap.h> +#include <linux/sched/mm.h> +#include <linux/fsnotify.h> +#include <linux/personality.h> +#include <linux/security.h> +#include <linux/syscalls.h> +#include <linux/mount.h> +#include <linux/audit.h> +#include <linux/capability.h> +#include <linux/file.h> +#include <linux/fcntl.h> +#include <linux/device_cgroup.h> +#include <linux/fs_struct.h> +#include <linux/posix_acl.h> +#include <linux/hash.h> +#include <linux/bitops.h> +#include <linux/init_task.h> +#include <linux/uaccess.h> + +#include <asm/runtime-const.h> + +#include "internal.h" +#include "mount.h" + +/* [Feb-1997 T. Schoebel-Theuer] + * Fundamental changes in the pathname lookup mechanisms (namei) + * were necessary because of omirr. The reason is that omirr needs + * to know the _real_ pathname, not the user-supplied one, in case + * of symlinks (and also when transname replacements occur). + * + * The new code replaces the old recursive symlink resolution with + * an iterative one (in case of non-nested symlink chains). It does + * this with calls to <fs>_follow_link(). + * As a side effect, dir_namei(), _namei() and follow_link() are now + * replaced with a single function lookup_dentry() that can handle all + * the special cases of the former code. + * + * With the new dcache, the pathname is stored at each inode, at least as + * long as the refcount of the inode is positive. As a side effect, the + * size of the dcache depends on the inode cache and thus is dynamic. + * + * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink + * resolution to correspond with current state of the code. + * + * Note that the symlink resolution is not *completely* iterative. + * There is still a significant amount of tail- and mid- recursion in + * the algorithm. Also, note that <fs>_readlink() is not used in + * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink() + * may return different results than <fs>_follow_link(). Many virtual + * filesystems (including /proc) exhibit this behavior. + */ + +/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation: + * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL + * and the name already exists in form of a symlink, try to create the new + * name indicated by the symlink. The old code always complained that the + * name already exists, due to not following the symlink even if its target + * is nonexistent. The new semantics affects also mknod() and link() when + * the name is a symlink pointing to a non-existent name. + * + * I don't know which semantics is the right one, since I have no access + * to standards. But I found by trial that HP-UX 9.0 has the full "new" + * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the + * "old" one. Personally, I think the new semantics is much more logical. + * Note that "ln old new" where "new" is a symlink pointing to a non-existing + * file does succeed in both HP-UX and SunOs, but not in Solaris + * and in the old Linux semantics. + */ + +/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink + * semantics. See the comments in "open_namei" and "do_link" below. + * + * [10-Sep-98 Alan Modra] Another symlink change. + */ + +/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks: + * inside the path - always follow. + * in the last component in creation/removal/renaming - never follow. + * if LOOKUP_FOLLOW passed - follow. + * if the pathname has trailing slashes - follow. + * otherwise - don't follow. + * (applied in that order). + * + * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT + * restored for 2.4. This is the last surviving part of old 4.2BSD bug. + * During the 2.4 we need to fix the userland stuff depending on it - + * hopefully we will be able to get rid of that wart in 2.5. So far only + * XEmacs seems to be relying on it... + */ +/* + * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland) + * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives + * any extra contention... + */ + +/* In order to reduce some races, while at the same time doing additional + * checking and hopefully speeding things up, we copy filenames to the + * kernel data space before using them.. + * + * POSIX.1 2.4: an empty pathname is invalid (ENOENT). + * PATH_MAX includes the nul terminator --RR. + */ + +/* SLAB cache for struct filename instances */ +static struct kmem_cache *__names_cache __ro_after_init; +#define names_cache runtime_const_ptr(__names_cache) + +/* + * Type of the last component on LOOKUP_PARENT + */ +enum last_type {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT}; + +void __init filename_init(void) +{ + __names_cache = kmem_cache_create_usercopy("names_cache", sizeof(struct filename), 0, + SLAB_HWCACHE_ALIGN|SLAB_PANIC, offsetof(struct filename, iname), + EMBEDDED_NAME_MAX, NULL); + runtime_const_init(ptr, __names_cache); +} + +static inline struct filename *alloc_filename(void) +{ + return kmem_cache_alloc(names_cache, GFP_KERNEL); +} + +static inline void free_filename(struct filename *p) +{ + kmem_cache_free(names_cache, p); +} + +static inline void initname(struct filename *name) +{ + name->aname = NULL; + name->refcnt = 1; +} + +static int getname_long(struct filename *name, const char __user *filename) +{ + int len; + char *p __free(kfree) = kmalloc(PATH_MAX, GFP_KERNEL); + if (unlikely(!p)) + return -ENOMEM; + + memcpy(p, &name->iname, EMBEDDED_NAME_MAX); + len = strncpy_from_user(p + EMBEDDED_NAME_MAX, + filename + EMBEDDED_NAME_MAX, + PATH_MAX - EMBEDDED_NAME_MAX); + if (unlikely(len < 0)) + return len; + if (unlikely(len == PATH_MAX - EMBEDDED_NAME_MAX)) + return -ENAMETOOLONG; + name->name = no_free_ptr(p); + return 0; +} + +static struct filename * +do_getname(const char __user *filename, int flags, bool incomplete) +{ + struct filename *result; + char *kname; + int len; + + result = alloc_filename(); + if (unlikely(!result)) + return ERR_PTR(-ENOMEM); + + /* + * First, try to embed the struct filename inside the names_cache + * allocation + */ + kname = (char *)result->iname; + result->name = kname; + + len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX); + /* + * Handle both empty path and copy failure in one go. + */ + if (unlikely(len <= 0)) { + /* The empty path is special. */ + if (!len && !(flags & LOOKUP_EMPTY)) + len = -ENOENT; + } + + /* + * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a + * separate struct filename so we can dedicate the entire + * names_cache allocation for the pathname, and re-do the copy from + * userland. + */ + if (unlikely(len == EMBEDDED_NAME_MAX)) + len = getname_long(result, filename); + if (unlikely(len < 0)) { + free_filename(result); + return ERR_PTR(len); + } + + initname(result); + if (likely(!incomplete)) + audit_getname(result); + return result; +} + +struct filename * +getname_flags(const char __user *filename, int flags) +{ + return do_getname(filename, flags, false); +} + +struct filename *getname_uflags(const char __user *filename, int uflags) +{ + int flags = (uflags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0; + + return getname_flags(filename, flags); +} + +struct filename *__getname_maybe_null(const char __user *pathname) +{ + char c; + + /* try to save on allocations; loss on um, though */ + if (get_user(c, pathname)) + return ERR_PTR(-EFAULT); + if (!c) + return NULL; + + CLASS(filename_flags, name)(pathname, LOOKUP_EMPTY); + /* empty pathname translates to NULL */ + if (!IS_ERR(name) && !(name->name[0])) + return NULL; + return no_free_ptr(name); +} + +static struct filename *do_getname_kernel(const char *filename, bool incomplete) +{ + struct filename *result; + int len = strlen(filename) + 1; + char *p; + + if (unlikely(len > PATH_MAX)) + return ERR_PTR(-ENAMETOOLONG); + + result = alloc_filename(); + if (unlikely(!result)) + return ERR_PTR(-ENOMEM); + + if (len <= EMBEDDED_NAME_MAX) { + p = (char *)result->iname; + memcpy(p, filename, len); + } else { + p = kmemdup(filename, len, GFP_KERNEL); + if (unlikely(!p)) { + free_filename(result); + return ERR_PTR(-ENOMEM); + } + } + result->name = p; + initname(result); + if (likely(!incomplete)) + audit_getname(result); + return result; +} + +struct filename *getname_kernel(const char *filename) +{ + return do_getname_kernel(filename, false); +} +EXPORT_SYMBOL(getname_kernel); + +void putname(struct filename *name) +{ + int refcnt; + + if (IS_ERR_OR_NULL(name)) + return; + + refcnt = name->refcnt; + if (unlikely(refcnt != 1)) { + if (WARN_ON_ONCE(!refcnt)) + return; + + name->refcnt--; + return; + } + + if (unlikely(name->name != name->iname)) + kfree(name->name); + free_filename(name); +} +EXPORT_SYMBOL(putname); + +static inline int __delayed_getname(struct delayed_filename *v, + const char __user *string, int flags) +{ + v->__incomplete_filename = do_getname(string, flags, true); + return PTR_ERR_OR_ZERO(v->__incomplete_filename); +} + +int delayed_getname(struct delayed_filename *v, const char __user *string) +{ + return __delayed_getname(v, string, 0); +} + +int delayed_getname_uflags(struct delayed_filename *v, const char __user *string, + int uflags) +{ + int flags = (uflags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0; + return __delayed_getname(v, string, flags); +} + +int putname_to_delayed(struct delayed_filename *v, struct filename *name) +{ + if (likely(name->refcnt == 1)) { + v->__incomplete_filename = name; + return 0; + } + name->refcnt--; + v->__incomplete_filename = do_getname_kernel(name->name, true); + return PTR_ERR_OR_ZERO(v->__incomplete_filename); +} + +void dismiss_delayed_filename(struct delayed_filename *v) +{ + putname(no_free_ptr(v->__incomplete_filename)); +} + +struct filename *complete_getname(struct delayed_filename *v) +{ + struct filename *res = no_free_ptr(v->__incomplete_filename); + if (!IS_ERR(res)) + audit_getname(res); + return res; +} + +/** + * check_acl - perform ACL permission checking + * @idmap: idmap of the mount the inode was found from + * @inode: inode to check permissions on + * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...) + * + * This function performs the ACL permission checking. Since this function + * retrieve POSIX acls it needs to know whether it is called from a blocking or + * non-blocking context and thus cares about the MAY_NOT_BLOCK bit. + * + * If the inode has been found through an idmapped mount the idmap of + * the vfsmount must be passed through @idmap. This function will then take + * care to map the inode according to @idmap before checking permissions. + * On non-idmapped mounts or if permission checking is to be performed on the + * raw inode simply pass @nop_mnt_idmap. + */ +static int check_acl(struct mnt_idmap *idmap, + struct inode *inode, int mask) +{ +#ifdef CONFIG_FS_POSIX_ACL + struct posix_acl *acl; + + if (mask & MAY_NOT_BLOCK) { + acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS); + if (!acl) + return -EAGAIN; + /* no ->get_inode_acl() calls in RCU mode... */ + if (is_uncached_acl(acl)) + return -ECHILD; + return posix_acl_permission(idmap, inode, acl, mask); + } + + acl = get_inode_acl(inode, ACL_TYPE_ACCESS); + if (IS_ERR(acl)) + return PTR_ERR(acl); + if (acl) { + int error = posix_acl_permission(idmap, inode, acl, mask); + posix_acl_release(acl); + return error; + } +#endif + + return -EAGAIN; +} + +/* + * Very quick optimistic "we know we have no ACL's" check. + * + * Note that this is purely for ACL_TYPE_ACCESS, and purely + * for the "we have cached that there are no ACLs" case. + * + * If this returns true, we know there are no ACLs. But if + * it returns false, we might still not have ACLs (it could + * be the is_uncached_acl() case). + */ +static inline bool no_acl_inode(struct inode *inode) +{ +#ifdef CONFIG_FS_POSIX_ACL + return likely(!READ_ONCE(inode->i_acl)); +#else + return true; +#endif +} + +/** + * acl_permission_check - perform basic UNIX permission checking + * @idmap: idmap of the mount the inode was found from + * @inode: inode to check permissions on + * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...) + * + * This function performs the basic UNIX permission checking. Since this + * function may retrieve POSIX acls it needs to know whether it is called from a + * blocking or non-blocking context and thus cares about the MAY_NOT_BLOCK bit. + * + * If the inode has been found through an idmapped mount the idmap of + * the vfsmount must be passed through @idmap. This function will then take + * care to map the inode according to @idmap before checking permissions. + * On non-idmapped mounts or if permission checking is to be performed on the + * raw inode simply pass @nop_mnt_idmap. + */ +static int acl_permission_check(struct mnt_idmap *idmap, + struct inode *inode, int mask) +{ + unsigned int mode = inode->i_mode; + vfsuid_t vfsuid; + + /* + * Common cheap case: everybody has the requested + * rights, and there are no ACLs to check. No need + * to do any owner/group checks in that case. + * + * - 'mask&7' is the requested permission bit set + * - multiplying by 0111 spreads them out to all of ugo + * - '& ~mode' looks for missing inode permission bits + * - the '!' is for "no missing permissions" + * + * After that, we just need to check that there are no + * ACL's on the inode - do the 'IS_POSIXACL()' check last + * because it will dereference the ->i_sb pointer and we + * want to avoid that if at all possible. + */ + if (!((mask & 7) * 0111 & ~mode)) { + if (no_acl_inode(inode)) + return 0; + if (!IS_POSIXACL(inode)) + return 0; + } + + /* Are we the owner? If so, ACL's don't matter */ + vfsuid = i_uid_into_vfsuid(idmap, inode); + if (likely(vfsuid_eq_kuid(vfsuid, current_fsuid()))) { + mask &= 7; + mode >>= 6; + return (mask & ~mode) ? -EACCES : 0; + } + + /* Do we have ACL's? */ + if (IS_POSIXACL(inode) && (mode & S_IRWXG)) { + int error = check_acl(idmap, inode, mask); + if (error != -EAGAIN) + return error; + } + + /* Only RWX matters for group/other mode bits */ + mask &= 7; + + /* + * Are the group permissions different from + * the other permissions in the bits we care + * about? Need to check group ownership if so. + */ + if (mask & (mode ^ (mode >> 3))) { + vfsgid_t vfsgid = i_gid_into_vfsgid(idmap, inode); + if (vfsgid_in_group_p(vfsgid)) + mode >>= 3; + } + + /* Bits in 'mode' clear that we require? */ + return (mask & ~mode) ? -EACCES : 0; +} + +/** + * generic_permission - check for access rights on a Posix-like filesystem + * @idmap: idmap of the mount the inode was found from + * @inode: inode to check access rights for + * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, + * %MAY_NOT_BLOCK ...) + * + * Used to check for read/write/execute permissions on a file. + * We use "fsuid" for this, letting us set arbitrary permissions + * for filesystem access without changing the "normal" uids which + * are used for other things. + * + * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk + * request cannot be satisfied (eg. requires blocking or too much complexity). + * It would then be called again in ref-walk mode. + * + * If the inode has been found through an idmapped mount the idmap of + * the vfsmount must be passed through @idmap. This function will then take + * care to map the inode according to @idmap before checking permissions. + * On non-idmapped mounts or if permission checking is to be performed on the + * raw inode simply pass @nop_mnt_idmap. + */ +int generic_permission(struct mnt_idmap *idmap, struct inode *inode, + int mask) +{ + int ret; + + /* + * Do the basic permission checks. + */ + ret = acl_permission_check(idmap, inode, mask); + if (ret != -EACCES) + return ret; + + if (S_ISDIR(inode->i_mode)) { + /* DACs are overridable for directories */ + if (!(mask & MAY_WRITE)) + if (capable_wrt_inode_uidgid(idmap, inode, + CAP_DAC_READ_SEARCH)) + return 0; + if (capable_wrt_inode_uidgid(idmap, inode, + CAP_DAC_OVERRIDE)) + return 0; + return -EACCES; + } + + /* + * Searching includes executable on directories, else just read. + */ + mask &= MAY_READ | MAY_WRITE | MAY_EXEC; + if (mask == MAY_READ) + if (capable_wrt_inode_uidgid(idmap, inode, + CAP_DAC_READ_SEARCH)) + return 0; + /* + * Read/write DACs are always overridable. + * Executable DACs are overridable when there is + * at least one exec bit set. + */ + if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO)) + if (capable_wrt_inode_uidgid(idmap, inode, + CAP_DAC_OVERRIDE)) + return 0; + + return -EACCES; +} +EXPORT_SYMBOL(generic_permission); + +/** + * do_inode_permission - UNIX permission checking + * @idmap: idmap of the mount the inode was found from + * @inode: inode to check permissions on + * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...) + * + * We _really_ want to just do "generic_permission()" without + * even looking at the inode->i_op values. So we keep a cache + * flag in inode->i_opflags, that says "this has not special + * permission function, use the fast case". + */ +static inline int do_inode_permission(struct mnt_idmap *idmap, + struct inode *inode, int mask) +{ + if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) { + if (likely(inode->i_op->permission)) + return inode->i_op->permission(idmap, inode, mask); + + /* This gets set once for the inode lifetime */ + spin_lock(&inode->i_lock); + inode->i_opflags |= IOP_FASTPERM; + spin_unlock(&inode->i_lock); + } + return generic_permission(idmap, inode, mask); +} + +/** + * sb_permission - Check superblock-level permissions + * @sb: Superblock of inode to check permission on + * @inode: Inode to check permission on + * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) + * + * Separate out file-system wide checks from inode-specific permission checks. + * + * Note: lookup_inode_permission_may_exec() does not call here. If you add + * MAY_EXEC checks, adjust it. + */ +static int sb_permission(struct super_block *sb, struct inode *inode, int mask) +{ + if (mask & MAY_WRITE) { + umode_t mode = inode->i_mode; + + /* Nobody gets write access to a read-only fs. */ + if (sb_rdonly(sb) && (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) + return -EROFS; + } + return 0; +} + +/** + * inode_permission - Check for access rights to a given inode + * @idmap: idmap of the mount the inode was found from + * @inode: Inode to check permission on + * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) + * + * Check for read/write/execute permissions on an inode. We use fs[ug]id for + * this, letting us set arbitrary permissions for filesystem access without + * changing the "normal" UIDs which are used for other things. + * + * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. + */ +int inode_permission(struct mnt_idmap *idmap, + struct inode *inode, int mask) +{ + int retval; + + retval = sb_permission(inode->i_sb, inode, mask); + if (unlikely(retval)) + return retval; + + if (mask & MAY_WRITE) { + /* + * Nobody gets write access to an immutable file. + */ + if (unlikely(IS_IMMUTABLE(inode))) + return -EPERM; + + /* + * Updating mtime will likely cause i_uid and i_gid to be + * written back improperly if their true value is unknown + * to the vfs. + */ + if (unlikely(HAS_UNMAPPED_ID(idmap, inode))) + return -EACCES; + } + + retval = do_inode_permission(idmap, inode, mask); + if (unlikely(retval)) + return retval; + + retval = devcgroup_inode_permission(inode, mask); + if (unlikely(retval)) + return retval; + + return security_inode_permission(inode, mask); +} +EXPORT_SYMBOL(inode_permission); + +/* + * lookup_inode_permission_may_exec - Check traversal right for given inode + * + * This is a special case routine for may_lookup() making assumptions specific + * to path traversal. Use inode_permission() if you are doing something else. + * + * Work is shaved off compared to inode_permission() as follows: + * - we know for a fact there is no MAY_WRITE to worry about + * - it is an invariant the inode is a directory + * + * Since majority of real-world traversal happens on inodes which grant it for + * everyone, we check it upfront and only resort to more expensive work if it + * fails. + * + * Filesystems which have their own ->permission hook and consequently miss out + * on IOP_FASTPERM can still get the optimization if they set IOP_FASTPERM_MAY_EXEC + * on their directory inodes. + */ +static __always_inline int lookup_inode_permission_may_exec(struct mnt_idmap *idmap, + struct inode *inode, int mask) +{ + /* Lookup already checked this to return -ENOTDIR */ + VFS_BUG_ON_INODE(!S_ISDIR(inode->i_mode), inode); + VFS_BUG_ON((mask & ~MAY_NOT_BLOCK) != 0); + + mask |= MAY_EXEC; + + if (unlikely(!(inode->i_opflags & (IOP_FASTPERM | IOP_FASTPERM_MAY_EXEC)))) + return inode_permission(idmap, inode, mask); + + if (unlikely(((inode->i_mode & 0111) != 0111) || !no_acl_inode(inode))) + return inode_permission(idmap, inode, mask); + + return security_inode_permission(inode, mask); +} + +/** + * path_get - get a reference to a path + * @path: path to get the reference to + * + * Given a path increment the reference count to the dentry and the vfsmount. + */ +void path_get(const struct path *path) +{ + mntget(path->mnt); + dget(path->dentry); +} +EXPORT_SYMBOL(path_get); + +/** + * path_put - put a reference to a path + * @path: path to put the reference to + * + * Given a path decrement the reference count to the dentry and the vfsmount. + */ +void path_put(const struct path *path) +{ + dput(path->dentry); + mntput(path->mnt); +} +EXPORT_SYMBOL(path_put); + +#define EMBEDDED_LEVELS 2 +struct nameidata { + struct path path; + struct qstr last; + struct path root; + struct inode *inode; /* path.dentry.d_inode */ + unsigned int flags, state; + unsigned seq, next_seq, m_seq, r_seq; + enum last_type last_type; + unsigned depth; + int total_link_count; + struct saved { + struct path link; + struct delayed_call done; + const char *name; + unsigned seq; + } *stack, internal[EMBEDDED_LEVELS]; + struct filename *name; + const char *pathname; + struct nameidata *saved; + unsigned root_seq; + int dfd; + vfsuid_t dir_vfsuid; + umode_t dir_mode; +} __randomize_layout; + +#define ND_ROOT_PRESET 1 +#define ND_ROOT_GRABBED 2 +#define ND_JUMPED 4 + +static void __set_nameidata(struct nameidata *p, int dfd, struct filename *name) +{ + struct nameidata *old = current->nameidata; + p->stack = p->internal; + p->depth = 0; + p->dfd = dfd; + p->name = name; + p->pathname = likely(name) ? name->name : ""; + p->path.mnt = NULL; + p->path.dentry = NULL; + p->total_link_count = old ? old->total_link_count : 0; + p->saved = old; + current->nameidata = p; +} + +static inline void set_nameidata(struct nameidata *p, int dfd, struct filename *name, + const struct path *root) +{ + __set_nameidata(p, dfd, name); + p->state = 0; + if (unlikely(root)) { + p->state = ND_ROOT_PRESET; + p->root = *root; + } +} + +static void restore_nameidata(void) +{ + struct nameidata *now = current->nameidata, *old = now->saved; + + current->nameidata = old; + if (old) + old->total_link_count = now->total_link_count; + if (now->stack != now->internal) + kfree(now->stack); +} + +static bool nd_alloc_stack(struct nameidata *nd) +{ + struct saved *p; + + p= kmalloc_objs(struct saved, MAXSYMLINKS, + nd->flags & LOOKUP_RCU ? GFP_ATOMIC : GFP_KERNEL); + if (unlikely(!p)) + return false; + memcpy(p, nd->internal, sizeof(nd->internal)); + nd->stack = p; + return true; +} + +/** + * path_connected - Verify that a dentry is below mnt.mnt_root + * @mnt: The mountpoint to check. + * @dentry: The dentry to check. + * + * Rename can sometimes move a file or directory outside of a bind + * mount, path_connected allows those cases to be detected. + */ +static bool path_connected(struct vfsmount *mnt, struct dentry *dentry) +{ + struct super_block *sb = mnt->mnt_sb; + + /* Bind mounts can have disconnected paths */ + if (mnt->mnt_root == sb->s_root) + return true; + + return is_subdir(dentry, mnt->mnt_root); +} + +static void drop_links(struct nameidata *nd) +{ + int i = nd->depth; + while (i--) { + struct saved *last = nd->stack + i; + do_delayed_call(&last->done); + clear_delayed_call(&last->done); + } +} + +static void leave_rcu(struct nameidata *nd) +{ + nd->flags &= ~LOOKUP_RCU; + nd->seq = nd->next_seq = 0; + rcu_read_unlock(); +} + +static void terminate_walk(struct nameidata *nd) +{ + if (unlikely(nd->depth)) + drop_links(nd); + if (!(nd->flags & LOOKUP_RCU)) { + int i; + path_put(&nd->path); + for (i = 0; i < nd->depth; i++) + path_put(&nd->stack[i].link); + if (nd->state & ND_ROOT_GRABBED) { + path_put(&nd->root); + nd->state &= ~ND_ROOT_GRABBED; + } + } else { + leave_rcu(nd); + } + nd->depth = 0; + nd->path.mnt = NULL; + nd->path.dentry = NULL; +} + +/* path_put is needed afterwards regardless of success or failure */ +static bool __legitimize_path(struct path *path, unsigned seq, unsigned mseq) +{ + int res = __legitimize_mnt(path->mnt, mseq); + if (unlikely(res)) { + if (res > 0) + path->mnt = NULL; + path->dentry = NULL; + return false; + } + if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) { + path->dentry = NULL; + return false; + } + return !read_seqcount_retry(&path->dentry->d_seq, seq); +} + +static inline bool legitimize_path(struct nameidata *nd, + struct path *path, unsigned seq) +{ + return __legitimize_path(path, seq, nd->m_seq); +} + +static bool legitimize_links(struct nameidata *nd) +{ + int i; + + VFS_BUG_ON(nd->flags & LOOKUP_CACHED); + + for (i = 0; i < nd->depth; i++) { + struct saved *last = nd->stack + i; + if (unlikely(!legitimize_path(nd, &last->link, last->seq))) { + drop_links(nd); + nd->depth = i + 1; + return false; + } + } + return true; +} + +static bool legitimize_root(struct nameidata *nd) +{ + /* Nothing to do if nd->root is zero or is managed by the VFS user. */ + if (!nd->root.mnt || (nd->state & ND_ROOT_PRESET)) + return true; + nd->state |= ND_ROOT_GRABBED; + return legitimize_path(nd, &nd->root, nd->root_seq); +} + +/* + * Path walking has 2 modes, rcu-walk and ref-walk (see + * Documentation/filesystems/path-lookup.txt). In situations when we can't + * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab + * normal reference counts on dentries and vfsmounts to transition to ref-walk + * mode. Refcounts are grabbed at the last known good point before rcu-walk + * got stuck, so ref-walk may continue from there. If this is not successful + * (eg. a seqcount has changed), then failure is returned and it's up to caller + * to restart the path walk from the beginning in ref-walk mode. + */ + +/** + * try_to_unlazy - try to switch to ref-walk mode. + * @nd: nameidata pathwalk data + * Returns: true on success, false on failure + * + * try_to_unlazy attempts to legitimize the current nd->path and nd->root + * for ref-walk mode. + * Must be called from rcu-walk context. + * Nothing should touch nameidata between try_to_unlazy() failure and + * terminate_walk(). + */ +static bool try_to_unlazy(struct nameidata *nd) +{ + struct dentry *parent = nd->path.dentry; + + VFS_BUG_ON(!(nd->flags & LOOKUP_RCU)); + + if (unlikely(nd->flags & LOOKUP_CACHED)) { + drop_links(nd); + nd->depth = 0; + goto out1; + } + if (unlikely(nd->depth && !legitimize_links(nd))) + goto out1; + if (unlikely(!legitimize_path(nd, &nd->path, nd->seq))) + goto out; + if (unlikely(!legitimize_root(nd))) + goto out; + leave_rcu(nd); + BUG_ON(nd->inode != parent->d_inode); + return true; + +out1: + nd->path.mnt = NULL; + nd->path.dentry = NULL; +out: + leave_rcu(nd); + return false; +} + +/** + * try_to_unlazy_next - try to switch to ref-walk mode. + * @nd: nameidata pathwalk data + * @dentry: next dentry to step into + * Returns: true on success, false on failure + * + * Similar to try_to_unlazy(), but here we have the next dentry already + * picked by rcu-walk and want to legitimize that in addition to the current + * nd->path and nd->root for ref-walk mode. Must be called from rcu-walk context. + * Nothing should touch nameidata between try_to_unlazy_next() failure and + * terminate_walk(). + */ +static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry) +{ + int res; + + VFS_BUG_ON(!(nd->flags & LOOKUP_RCU)); + + if (unlikely(nd->flags & LOOKUP_CACHED)) { + drop_links(nd); + nd->depth = 0; + goto out2; + } + if (unlikely(nd->depth && !legitimize_links(nd))) + goto out2; + res = __legitimize_mnt(nd->path.mnt, nd->m_seq); + if (unlikely(res)) { + if (res > 0) + goto out2; + goto out1; + } + if (unlikely(!lockref_get_not_dead(&nd->path.dentry->d_lockref))) + goto out1; + + /* + * We need to move both the parent and the dentry from the RCU domain + * to be properly refcounted. And the sequence number in the dentry + * validates *both* dentry counters, since we checked the sequence + * number of the parent after we got the child sequence number. So we + * know the parent must still be valid if the child sequence number is + */ + if (unlikely(!lockref_get_not_dead(&dentry->d_lockref))) + goto out; + if (read_seqcount_retry(&dentry->d_seq, nd->next_seq)) + goto out_dput; + /* + * Sequence counts matched. Now make sure that the root is + * still valid and get it if required. + */ + if (unlikely(!legitimize_root(nd))) + goto out_dput; + leave_rcu(nd); + return true; + +out2: + nd->path.mnt = NULL; +out1: + nd->path.dentry = NULL; +out: + leave_rcu(nd); + return false; +out_dput: + leave_rcu(nd); + dput(dentry); + return false; +} + +static inline int d_revalidate(struct inode *dir, const struct qstr *name, + struct dentry *dentry, unsigned int flags) +{ + if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) + return dentry->d_op->d_revalidate(dir, name, dentry, flags); + else + return 1; +} + +/** + * complete_walk - successful completion of path walk + * @nd: pointer nameidata + * + * If we had been in RCU mode, drop out of it and legitimize nd->path. + * Revalidate the final result, unless we'd already done that during + * the path walk or the filesystem doesn't ask for it. Return 0 on + * success, -error on failure. In case of failure caller does not + * need to drop nd->path. + */ +static int complete_walk(struct nameidata *nd) +{ + struct dentry *dentry = nd->path.dentry; + int status; + + if (nd->flags & LOOKUP_RCU) { + /* + * We don't want to zero nd->root for scoped-lookups or + * externally-managed nd->root. + */ + if (likely(!(nd->state & ND_ROOT_PRESET))) + if (likely(!(nd->flags & LOOKUP_IS_SCOPED))) + nd->root.mnt = NULL; + nd->flags &= ~LOOKUP_CACHED; + if (!try_to_unlazy(nd)) + return -ECHILD; + } + + if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) { + /* + * While the guarantee of LOOKUP_IS_SCOPED is (roughly) "don't + * ever step outside the root during lookup" and should already + * be guaranteed by the rest of namei, we want to avoid a namei + * BUG resulting in userspace being given a path that was not + * scoped within the root at some point during the lookup. + * + * So, do a final sanity-check to make sure that in the + * worst-case scenario (a complete bypass of LOOKUP_IS_SCOPED) + * we won't silently return an fd completely outside of the + * requested root to userspace. + * + * Userspace could move the path outside the root after this + * check, but as discussed elsewhere this is not a concern (the + * resolved file was inside the root at some point). + */ + if (!path_is_under(&nd->path, &nd->root)) + return -EXDEV; + } + + if (likely(!(nd->state & ND_JUMPED))) + return 0; + + if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE))) + return 0; + + status = dentry->d_op->d_weak_revalidate(dentry, nd->flags); + if (status > 0) + return 0; + + if (!status) + status = -ESTALE; + + return status; +} + +static int set_root(struct nameidata *nd) +{ + struct fs_struct *fs = current->fs; + + /* + * Jumping to the real root in a scoped-lookup is a BUG in namei, but we + * still have to ensure it doesn't happen because it will cause a breakout + * from the dirfd. + */ + if (WARN_ON(nd->flags & LOOKUP_IS_SCOPED)) + return -ENOTRECOVERABLE; + + if (nd->flags & LOOKUP_RCU) { + unsigned seq; + + do { + seq = read_seqbegin(&fs->seq); + nd->root = fs->root; + nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq); + } while (read_seqretry(&fs->seq, seq)); + } else { + get_fs_root(fs, &nd->root); + nd->state |= ND_ROOT_GRABBED; + } + return 0; +} + +static int nd_jump_root(struct nameidata *nd) +{ + if (unlikely(nd->flags & LOOKUP_BENEATH)) + return -EXDEV; + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) { + /* Absolute path arguments to path_init() are allowed. */ + if (nd->path.mnt != NULL && nd->path.mnt != nd->root.mnt) + return -EXDEV; + } + if (!nd->root.mnt) { + int error = set_root(nd); + if (unlikely(error)) + return error; + } + if (nd->flags & LOOKUP_RCU) { + struct dentry *d; + nd->path = nd->root; + d = nd->path.dentry; + nd->inode = d->d_inode; + nd->seq = nd->root_seq; + if (read_seqcount_retry(&d->d_seq, nd->seq)) + return -ECHILD; + } else { + path_put(&nd->path); + nd->path = nd->root; + path_get(&nd->path); + nd->inode = nd->path.dentry->d_inode; + } + nd->state |= ND_JUMPED; + return 0; +} + +/* + * Helper to directly jump to a known parsed path from ->get_link, + * caller must have taken a reference to path beforehand. + */ +int nd_jump_link(const struct path *path) +{ + int error = -ELOOP; + struct nameidata *nd = current->nameidata; + + if (unlikely(nd->flags & LOOKUP_NO_MAGICLINKS)) + goto err; + + error = -EXDEV; + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) { + if (nd->path.mnt != path->mnt) + goto err; + } + /* Not currently safe for scoped-lookups. */ + if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) + goto err; + + path_put(&nd->path); + nd->path = *path; + nd->inode = nd->path.dentry->d_inode; + nd->state |= ND_JUMPED; + return 0; + +err: + path_put(path); + return error; +} + +static inline void put_link(struct nameidata *nd) +{ + struct saved *last = nd->stack + --nd->depth; + do_delayed_call(&last->done); + if (!(nd->flags & LOOKUP_RCU)) + path_put(&last->link); +} + +static int sysctl_protected_symlinks __read_mostly; +static int sysctl_protected_hardlinks __read_mostly; +static int sysctl_protected_fifos __read_mostly; +static int sysctl_protected_regular __read_mostly; + +#ifdef CONFIG_SYSCTL +static const struct ctl_table namei_sysctls[] = { + { + .procname = "protected_symlinks", + .data = &sysctl_protected_symlinks, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, + { + .procname = "protected_hardlinks", + .data = &sysctl_protected_hardlinks, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, + { + .procname = "protected_fifos", + .data = &sysctl_protected_fifos, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_TWO, + }, + { + .procname = "protected_regular", + .data = &sysctl_protected_regular, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_TWO, + }, +}; + +static int __init init_fs_namei_sysctls(void) +{ + register_sysctl_init("fs", namei_sysctls); + return 0; +} +fs_initcall(init_fs_namei_sysctls); + +#endif /* CONFIG_SYSCTL */ + +/** + * may_follow_link - Check symlink following for unsafe situations + * @nd: nameidata pathwalk data + * @inode: Used for idmapping. + * + * In the case of the sysctl_protected_symlinks sysctl being enabled, + * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is + * in a sticky world-writable directory. This is to protect privileged + * processes from failing races against path names that may change out + * from under them by way of other users creating malicious symlinks. + * It will permit symlinks to be followed only when outside a sticky + * world-writable directory, or when the uid of the symlink and follower + * match, or when the directory owner matches the symlink's owner. + * + * Returns 0 if following the symlink is allowed, -ve on error. + */ +static inline int may_follow_link(struct nameidata *nd, const struct inode *inode) +{ + struct mnt_idmap *idmap; + vfsuid_t vfsuid; + + if (!sysctl_protected_symlinks) + return 0; + + idmap = mnt_idmap(nd->path.mnt); + vfsuid = i_uid_into_vfsuid(idmap, inode); + /* Allowed if owner and follower match. */ + if (vfsuid_eq_kuid(vfsuid, current_fsuid())) + return 0; + + /* Allowed if parent directory not sticky and world-writable. */ + if ((nd->dir_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH)) + return 0; + + /* Allowed if parent directory and link owner match. */ + if (vfsuid_valid(nd->dir_vfsuid) && vfsuid_eq(nd->dir_vfsuid, vfsuid)) + return 0; + + if (nd->flags & LOOKUP_RCU) + return -ECHILD; + + audit_inode(nd->name, nd->stack[0].link.dentry, 0); + audit_log_path_denied(AUDIT_ANOM_LINK, "follow_link"); + return -EACCES; +} + +/** + * safe_hardlink_source - Check for safe hardlink conditions + * @idmap: idmap of the mount the inode was found from + * @inode: the source inode to hardlink from + * + * Return false if at least one of the following conditions: + * - inode is not a regular file + * - inode is setuid + * - inode is setgid and group-exec + * - access failure for read and write + * + * Otherwise returns true. + */ +static bool safe_hardlink_source(struct mnt_idmap *idmap, + struct inode *inode) +{ + umode_t mode = inode->i_mode; + + /* Special files should not get pinned to the filesystem. */ + if (!S_ISREG(mode)) + return false; + + /* Setuid files should not get pinned to the filesystem. */ + if (mode & S_ISUID) + return false; + + /* Executable setgid files should not get pinned to the filesystem. */ + if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) + return false; + + /* Hardlinking to unreadable or unwritable sources is dangerous. */ + if (inode_permission(idmap, inode, MAY_READ | MAY_WRITE)) + return false; + + return true; +} + +/** + * may_linkat - Check permissions for creating a hardlink + * @idmap: idmap of the mount the inode was found from + * @link: the source to hardlink from + * + * Block hardlink when all of: + * - sysctl_protected_hardlinks enabled + * - fsuid does not match inode + * - hardlink source is unsafe (see safe_hardlink_source() above) + * - not CAP_FOWNER in a namespace with the inode owner uid mapped + * + * If the inode has been found through an idmapped mount the idmap of + * the vfsmount must be passed through @idmap. This function will then take + * care to map the inode according to @idmap before checking permissions. + * On non-idmapped mounts or if permission checking is to be performed on the + * raw inode simply pass @nop_mnt_idmap. + * + * Returns 0 if successful, -ve on error. + */ +int may_linkat(struct mnt_idmap *idmap, const struct path *link) +{ + struct inode *inode = link->dentry->d_inode; + + /* Inode writeback is not safe when the uid or gid are invalid. */ + if (!vfsuid_valid(i_uid_into_vfsuid(idmap, inode)) || + !vfsgid_valid(i_gid_into_vfsgid(idmap, inode))) + return -EOVERFLOW; + + if (!sysctl_protected_hardlinks) + return 0; + + /* Source inode owner (or CAP_FOWNER) can hardlink all they like, + * otherwise, it must be a safe source. + */ + if (safe_hardlink_source(idmap, inode) || + inode_owner_or_capable(idmap, inode)) + return 0; + + audit_log_path_denied(AUDIT_ANOM_LINK, "linkat"); + return -EPERM; +} + +/** + * may_create_in_sticky - Check whether an O_CREAT open in a sticky directory + * should be allowed, or not, on files that already + * exist. + * @idmap: idmap of the mount the inode was found from + * @nd: nameidata pathwalk data + * @inode: the inode of the file to open + * + * Block an O_CREAT open of a FIFO (or a regular file) when: + * - sysctl_protected_fifos (or sysctl_protected_regular) is enabled + * - the file already exists + * - we are in a sticky directory + * - we don't own the file + * - the owner of the directory doesn't own the file + * - the directory is world writable + * If the sysctl_protected_fifos (or sysctl_protected_regular) is set to 2 + * the directory doesn't have to be world writable: being group writable will + * be enough. + * + * If the inode has been found through an idmapped mount the idmap of + * the vfsmount must be passed through @idmap. This function will then take + * care to map the inode according to @idmap before checking permissions. + * On non-idmapped mounts or if permission checking is to be performed on the + * raw inode simply pass @nop_mnt_idmap. + * + * Returns 0 if the open is allowed, -ve on error. + */ +static int may_create_in_sticky(struct mnt_idmap *idmap, struct nameidata *nd, + struct inode *const inode) +{ + umode_t dir_mode = nd->dir_mode; + vfsuid_t dir_vfsuid = nd->dir_vfsuid, i_vfsuid; + + if (likely(!(dir_mode & S_ISVTX))) + return 0; + + if (S_ISREG(inode->i_mode) && !sysctl_protected_regular) + return 0; + + if (S_ISFIFO(inode->i_mode) && !sysctl_protected_fifos) + return 0; + + i_vfsuid = i_uid_into_vfsuid(idmap, inode); + + if (vfsuid_eq(i_vfsuid, dir_vfsuid)) + return 0; + + if (vfsuid_eq_kuid(i_vfsuid, current_fsuid())) + return 0; + + if (likely(dir_mode & 0002)) { + audit_log_path_denied(AUDIT_ANOM_CREAT, "sticky_create"); + return -EACCES; + } + + if (dir_mode & 0020) { + if (sysctl_protected_fifos >= 2 && S_ISFIFO(inode->i_mode)) { + audit_log_path_denied(AUDIT_ANOM_CREAT, + "sticky_create_fifo"); + return -EACCES; + } + + if (sysctl_protected_regular >= 2 && S_ISREG(inode->i_mode)) { + audit_log_path_denied(AUDIT_ANOM_CREAT, + "sticky_create_regular"); + return -EACCES; + } + } + + return 0; +} + +/* + * follow_up - Find the mountpoint of path's vfsmount + * + * Given a path, find the mountpoint of its source file system. + * Replace @path with the path of the mountpoint in the parent mount. + * Up is towards /. + * + * Return 1 if we went up a level and 0 if we were already at the + * root. + */ +int follow_up(struct path *path) +{ + struct mount *mnt = real_mount(path->mnt); + struct mount *parent; + struct dentry *mountpoint; + + read_seqlock_excl(&mount_lock); + parent = mnt->mnt_parent; + if (parent == mnt) { + read_sequnlock_excl(&mount_lock); + return 0; + } + mntget(&parent->mnt); + mountpoint = dget(mnt->mnt_mountpoint); + read_sequnlock_excl(&mount_lock); + dput(path->dentry); + path->dentry = mountpoint; + mntput(path->mnt); + path->mnt = &parent->mnt; + return 1; +} +EXPORT_SYMBOL(follow_up); + +static bool choose_mountpoint_rcu(struct mount *m, const struct path *root, + struct path *path, unsigned *seqp) +{ + while (mnt_has_parent(m)) { + struct dentry *mountpoint = m->mnt_mountpoint; + + m = m->mnt_parent; + if (unlikely(root->dentry == mountpoint && + root->mnt == &m->mnt)) + break; + if (mountpoint != m->mnt.mnt_root) { + path->mnt = &m->mnt; + path->dentry = mountpoint; + *seqp = read_seqcount_begin(&mountpoint->d_seq); + return true; + } + } + return false; +} + +static bool choose_mountpoint(struct mount *m, const struct path *root, + struct path *path) +{ + bool found; + + rcu_read_lock(); + while (1) { + unsigned seq, mseq = read_seqbegin(&mount_lock); + + found = choose_mountpoint_rcu(m, root, path, &seq); + if (unlikely(!found)) { + if (!read_seqretry(&mount_lock, mseq)) + break; + } else { + if (likely(__legitimize_path(path, seq, mseq))) + break; + rcu_read_unlock(); + path_put(path); + rcu_read_lock(); + } + } + rcu_read_unlock(); + return found; +} + +/* + * Perform an automount + * - return -EISDIR to tell follow_managed() to stop and return the path we + * were called with. + */ +static int follow_automount(struct path *path, int *count, unsigned lookup_flags) +{ + struct dentry *dentry = path->dentry; + + /* We don't want to mount if someone's just doing a stat - + * unless they're stat'ing a directory and appended a '/' to + * the name. + * + * We do, however, want to mount if someone wants to open or + * create a file of any type under the mountpoint, wants to + * traverse through the mountpoint or wants to open the + * mounted directory. Also, autofs may mark negative dentries + * as being automount points. These will need the attentions + * of the daemon to instantiate them before they can be used. + */ + if (!(lookup_flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | + LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) && + dentry->d_inode) + return -EISDIR; + + /* No need to trigger automounts if mountpoint crossing is disabled. */ + if (lookup_flags & LOOKUP_NO_XDEV) + return -EXDEV; + + if (count && (*count)++ >= MAXSYMLINKS) + return -ELOOP; + + return finish_automount(dentry->d_op->d_automount(path), path); +} + +/* + * mount traversal - out-of-line part. One note on ->d_flags accesses - + * dentries are pinned but not locked here, so negative dentry can go + * positive right under us. Use of smp_load_acquire() provides a barrier + * sufficient for ->d_inode and ->d_flags consistency. + */ +static int __traverse_mounts(struct path *path, unsigned flags, bool *jumped, + int *count, unsigned lookup_flags) +{ + struct vfsmount *mnt = path->mnt; + bool need_mntput = false; + int ret = 0; + + while (flags & DCACHE_MANAGED_DENTRY) { + /* Allow the filesystem to manage the transit without i_rwsem + * being held. */ + if (flags & DCACHE_MANAGE_TRANSIT) { + if (lookup_flags & LOOKUP_NO_XDEV) { + ret = -EXDEV; + break; + } + ret = path->dentry->d_op->d_manage(path, false); + flags = smp_load_acquire(&path->dentry->d_flags); + if (ret < 0) + break; + } + + if (flags & DCACHE_MOUNTED) { // something's mounted on it.. + struct vfsmount *mounted = lookup_mnt(path); + if (mounted) { // ... in our namespace + dput(path->dentry); + if (need_mntput) + mntput(path->mnt); + path->mnt = mounted; + path->dentry = dget(mounted->mnt_root); + // here we know it's positive + flags = path->dentry->d_flags; + need_mntput = true; + if (unlikely(lookup_flags & LOOKUP_NO_XDEV)) { + ret = -EXDEV; + break; + } + continue; + } + } + + if (!(flags & DCACHE_NEED_AUTOMOUNT)) + break; + + // uncovered automount point + ret = follow_automount(path, count, lookup_flags); + flags = smp_load_acquire(&path->dentry->d_flags); + if (ret < 0) + break; + } + + if (ret == -EISDIR) + ret = 0; + // possible if you race with several mount --move + if (need_mntput && path->mnt == mnt) + mntput(path->mnt); + if (!ret && unlikely(d_flags_negative(flags))) + ret = -ENOENT; + *jumped = need_mntput; + return ret; +} + +static inline int traverse_mounts(struct path *path, bool *jumped, + int *count, unsigned lookup_flags) +{ + unsigned flags = smp_load_acquire(&path->dentry->d_flags); + + /* fastpath */ + if (likely(!(flags & DCACHE_MANAGED_DENTRY))) { + *jumped = false; + if (unlikely(d_flags_negative(flags))) + return -ENOENT; + return 0; + } + return __traverse_mounts(path, flags, jumped, count, lookup_flags); +} + +int follow_down_one(struct path *path) +{ + struct vfsmount *mounted; + + mounted = lookup_mnt(path); + if (mounted) { + dput(path->dentry); + mntput(path->mnt); + path->mnt = mounted; + path->dentry = dget(mounted->mnt_root); + return 1; + } + return 0; +} +EXPORT_SYMBOL(follow_down_one); + +/* + * Follow down to the covering mount currently visible to userspace. At each + * point, the filesystem owning that dentry may be queried as to whether the + * caller is permitted to proceed or not. + */ +int follow_down(struct path *path, unsigned int flags) +{ + struct vfsmount *mnt = path->mnt; + bool jumped; + int ret = traverse_mounts(path, &jumped, NULL, flags); + + if (path->mnt != mnt) + mntput(mnt); + return ret; +} +EXPORT_SYMBOL(follow_down); + +/* + * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if + * we meet a managed dentry that would need blocking. + */ +static bool __follow_mount_rcu(struct nameidata *nd, struct path *path) +{ + struct dentry *dentry = path->dentry; + unsigned int flags = dentry->d_flags; + + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) + return false; + + for (;;) { + /* + * Don't forget we might have a non-mountpoint managed dentry + * that wants to block transit. + */ + if (unlikely(flags & DCACHE_MANAGE_TRANSIT)) { + int res = dentry->d_op->d_manage(path, true); + if (res) + return res == -EISDIR; + flags = dentry->d_flags; + } + + if (flags & DCACHE_MOUNTED) { + struct mount *mounted = __lookup_mnt(path->mnt, dentry); + if (mounted) { + path->mnt = &mounted->mnt; + dentry = path->dentry = mounted->mnt.mnt_root; + nd->state |= ND_JUMPED; + nd->next_seq = read_seqcount_begin(&dentry->d_seq); + flags = dentry->d_flags; + // makes sure that non-RCU pathwalk could reach + // this state. + if (read_seqretry(&mount_lock, nd->m_seq)) + return false; + continue; + } + if (read_seqretry(&mount_lock, nd->m_seq)) + return false; + } + return !(flags & DCACHE_NEED_AUTOMOUNT); + } +} + +static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry, + struct path *path) +{ + bool jumped; + int ret; + + path->mnt = nd->path.mnt; + path->dentry = dentry; + if (nd->flags & LOOKUP_RCU) { + unsigned int seq = nd->next_seq; + if (likely(!d_managed(dentry))) + return 0; + if (likely(__follow_mount_rcu(nd, path))) + return 0; + // *path and nd->next_seq might've been clobbered + path->mnt = nd->path.mnt; + path->dentry = dentry; + nd->next_seq = seq; + if (unlikely(!try_to_unlazy_next(nd, dentry))) + return -ECHILD; + } + ret = traverse_mounts(path, &jumped, &nd->total_link_count, nd->flags); + if (jumped) + nd->state |= ND_JUMPED; + if (unlikely(ret)) { + dput(path->dentry); + if (path->mnt != nd->path.mnt) + mntput(path->mnt); + } + return ret; +} + +/* + * This looks up the name in dcache and possibly revalidates the found dentry. + * NULL is returned if the dentry does not exist in the cache. + */ +static struct dentry *lookup_dcache(const struct qstr *name, + struct dentry *dir, + unsigned int flags) +{ + struct dentry *dentry = d_lookup(dir, name); + if (dentry) { + int error = d_revalidate(dir->d_inode, name, dentry, flags); + if (unlikely(error <= 0)) { + if (!error) + d_invalidate(dentry); + dput(dentry); + return ERR_PTR(error); + } + } + return dentry; +} + +/* + * Parent directory has inode locked exclusive. This is one + * and only case when ->lookup() gets called on non in-lookup + * dentries - as the matter of fact, this only gets called + * when directory is guaranteed to have no in-lookup children + * at all. + * Will return -ENOENT if name isn't found and LOOKUP_CREATE wasn't passed. + * Will return -EEXIST if name is found and LOOKUP_EXCL was passed. + */ +static struct dentry *lookup_one_qstr_excl(const struct qstr *name, + struct dentry *base, unsigned int flags) +{ + struct dentry *dentry; + struct dentry *old; + struct inode *dir; + + dentry = lookup_dcache(name, base, flags); + if (dentry) + goto found; + + /* Don't create child dentry for a dead directory. */ + dir = base->d_inode; + if (unlikely(IS_DEADDIR(dir))) + return ERR_PTR(-ENOENT); + + dentry = d_alloc(base, name); + if (unlikely(!dentry)) + return ERR_PTR(-ENOMEM); + + old = dir->i_op->lookup(dir, dentry, flags); + if (unlikely(old)) { + dput(dentry); + dentry = old; + } +found: + if (IS_ERR(dentry)) + return dentry; + if (d_is_negative(dentry) && !(flags & LOOKUP_CREATE)) { + dput(dentry); + return ERR_PTR(-ENOENT); + } + if (d_is_positive(dentry) && (flags & LOOKUP_EXCL)) { + dput(dentry); + return ERR_PTR(-EEXIST); + } + return dentry; +} + +/** + * lookup_fast - do fast lockless (but racy) lookup of a dentry + * @nd: current nameidata + * + * Do a fast, but racy lookup in the dcache for the given dentry, and + * revalidate it. Returns a valid dentry pointer or NULL if one wasn't + * found. On error, an ERR_PTR will be returned. + * + * If this function returns a valid dentry and the walk is no longer + * lazy, the dentry will carry a reference that must later be put. If + * RCU mode is still in force, then this is not the case and the dentry + * must be legitimized before use. If this returns NULL, then the walk + * will no longer be in RCU mode. + */ +static struct dentry *lookup_fast(struct nameidata *nd) +{ + struct dentry *dentry, *parent = nd->path.dentry; + int status = 1; + + /* + * Rename seqlock is not required here because in the off chance + * of a false negative due to a concurrent rename, the caller is + * going to fall back to non-racy lookup. + */ + if (nd->flags & LOOKUP_RCU) { + dentry = __d_lookup_rcu(parent, &nd->last, &nd->next_seq); + if (unlikely(!dentry)) { + if (!try_to_unlazy(nd)) + return ERR_PTR(-ECHILD); + return NULL; + } + + /* + * This sequence count validates that the parent had no + * changes while we did the lookup of the dentry above. + */ + if (read_seqcount_retry(&parent->d_seq, nd->seq)) + return ERR_PTR(-ECHILD); + + status = d_revalidate(nd->inode, &nd->last, dentry, nd->flags); + if (likely(status > 0)) + return dentry; + if (!try_to_unlazy_next(nd, dentry)) + return ERR_PTR(-ECHILD); + if (status == -ECHILD) + /* we'd been told to redo it in non-rcu mode */ + status = d_revalidate(nd->inode, &nd->last, + dentry, nd->flags); + } else { + dentry = __d_lookup(parent, &nd->last); + if (unlikely(!dentry)) + return NULL; + status = d_revalidate(nd->inode, &nd->last, dentry, nd->flags); + } + if (unlikely(status <= 0)) { + if (!status) + d_invalidate(dentry); + dput(dentry); + return ERR_PTR(status); + } + return dentry; +} + +/* Fast lookup failed, do it the slow way */ +static struct dentry *__lookup_slow(const struct qstr *name, + struct dentry *dir, + unsigned int flags) +{ + struct dentry *dentry, *old; + struct inode *inode = dir->d_inode; + + /* Don't go there if it's already dead */ + if (unlikely(IS_DEADDIR(inode))) + return ERR_PTR(-ENOENT); +again: + dentry = d_alloc_parallel(dir, name); + if (IS_ERR(dentry)) + return dentry; + if (unlikely(!d_in_lookup(dentry))) { + int error = d_revalidate(inode, name, dentry, flags); + if (unlikely(error <= 0)) { + if (!error) { + d_invalidate(dentry); + dput(dentry); + goto again; + } + dput(dentry); + dentry = ERR_PTR(error); + } + } else { + old = inode->i_op->lookup(inode, dentry, flags); + d_lookup_done(dentry); + if (unlikely(old)) { + dput(dentry); + dentry = old; + } + } + return dentry; +} + +static noinline struct dentry *lookup_slow(const struct qstr *name, + struct dentry *dir, + unsigned int flags) +{ + struct inode *inode = dir->d_inode; + struct dentry *res; + inode_lock_shared(inode); + res = __lookup_slow(name, dir, flags); + inode_unlock_shared(inode); + return res; +} + +static struct dentry *lookup_slow_killable(const struct qstr *name, + struct dentry *dir, + unsigned int flags) +{ + struct inode *inode = dir->d_inode; + struct dentry *res; + + if (inode_lock_shared_killable(inode)) + return ERR_PTR(-EINTR); + res = __lookup_slow(name, dir, flags); + inode_unlock_shared(inode); + return res; +} + +static inline int may_lookup(struct mnt_idmap *idmap, + struct nameidata *restrict nd) +{ + int err, mask; + + mask = nd->flags & LOOKUP_RCU ? MAY_NOT_BLOCK : 0; + err = lookup_inode_permission_may_exec(idmap, nd->inode, mask); + if (likely(!err)) + return 0; + + // If we failed, and we weren't in LOOKUP_RCU, it's final + if (!(nd->flags & LOOKUP_RCU)) + return err; + + // Drop out of RCU mode to make sure it wasn't transient + if (!try_to_unlazy(nd)) + return -ECHILD; // redo it all non-lazy + + if (err != -ECHILD) // hard error + return err; + + return lookup_inode_permission_may_exec(idmap, nd->inode, 0); +} + +static int reserve_stack(struct nameidata *nd, struct path *link) +{ + if (unlikely(nd->total_link_count++ >= MAXSYMLINKS)) + return -ELOOP; + + if (likely(nd->depth != EMBEDDED_LEVELS)) + return 0; + if (likely(nd->stack != nd->internal)) + return 0; + if (likely(nd_alloc_stack(nd))) + return 0; + + if (nd->flags & LOOKUP_RCU) { + // we need to grab link before we do unlazy. And we can't skip + // unlazy even if we fail to grab the link - cleanup needs it + bool grabbed_link = legitimize_path(nd, link, nd->next_seq); + + if (!try_to_unlazy(nd) || !grabbed_link) + return -ECHILD; + + if (nd_alloc_stack(nd)) + return 0; + } + return -ENOMEM; +} + +enum {WALK_TRAILING = 1, WALK_MORE = 2, WALK_NOFOLLOW = 4}; + +static noinline const char *pick_link(struct nameidata *nd, struct path *link, + struct inode *inode, int flags) +{ + struct saved *last; + const char *res; + int error; + + if (nd->flags & LOOKUP_RCU) { + /* make sure that d_is_symlink from step_into_slowpath() matches the inode */ + if (read_seqcount_retry(&link->dentry->d_seq, nd->next_seq)) + return ERR_PTR(-ECHILD); + } else { + if (link->mnt == nd->path.mnt) + mntget(link->mnt); + } + + error = reserve_stack(nd, link); + if (unlikely(error)) { + if (!(nd->flags & LOOKUP_RCU)) + path_put(link); + return ERR_PTR(error); + } + last = nd->stack + nd->depth++; + last->link = *link; + clear_delayed_call(&last->done); + last->seq = nd->next_seq; + + if (flags & WALK_TRAILING) { + error = may_follow_link(nd, inode); + if (unlikely(error)) + return ERR_PTR(error); + } + + if (unlikely(nd->flags & LOOKUP_NO_SYMLINKS) || + unlikely(link->mnt->mnt_flags & MNT_NOSYMFOLLOW)) + return ERR_PTR(-ELOOP); + + if (unlikely(atime_needs_update(&last->link, inode))) { + if (nd->flags & LOOKUP_RCU) { + if (!try_to_unlazy(nd)) + return ERR_PTR(-ECHILD); + } + touch_atime(&last->link); + cond_resched(); + } + + error = security_inode_follow_link(link->dentry, inode, + nd->flags & LOOKUP_RCU); + if (unlikely(error)) + return ERR_PTR(error); + + res = READ_ONCE(inode->i_link); + if (!res) { + const char * (*get)(struct dentry *, struct inode *, + struct delayed_call *); + get = inode->i_op->get_link; + if (nd->flags & LOOKUP_RCU) { + res = get(NULL, inode, &last->done); + if (res == ERR_PTR(-ECHILD) && try_to_unlazy(nd)) + res = get(link->dentry, inode, &last->done); + } else { + res = get(link->dentry, inode, &last->done); + } + if (!res) + goto all_done; + if (IS_ERR(res)) + return res; + } + if (*res == '/') { + error = nd_jump_root(nd); + if (unlikely(error)) + return ERR_PTR(error); + while (unlikely(*++res == '/')) + ; + } + if (*res) + return res; +all_done: // pure jump + put_link(nd); + return NULL; +} + +/* + * Do we need to follow links? We _really_ want to be able + * to do this check without having to look at inode->i_op, + * so we keep a cache of "no, this doesn't need follow_link" + * for the common case. + * + * NOTE: dentry must be what nd->next_seq had been sampled from. + */ +static noinline const char *step_into_slowpath(struct nameidata *nd, int flags, + struct dentry *dentry) +{ + struct path path; + struct inode *inode; + int err; + + err = handle_mounts(nd, dentry, &path); + if (unlikely(err < 0)) + return ERR_PTR(err); + inode = path.dentry->d_inode; + if (likely(!d_is_symlink(path.dentry)) || + ((flags & WALK_TRAILING) && !(nd->flags & LOOKUP_FOLLOW)) || + (flags & WALK_NOFOLLOW)) { + /* not a symlink or should not follow */ + if (nd->flags & LOOKUP_RCU) { + if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq)) + return ERR_PTR(-ECHILD); + if (unlikely(!inode)) + return ERR_PTR(-ENOENT); + } else { + dput(nd->path.dentry); + if (nd->path.mnt != path.mnt) + mntput(nd->path.mnt); + } + nd->path = path; + nd->inode = inode; + nd->seq = nd->next_seq; + return NULL; + } + return pick_link(nd, &path, inode, flags); +} + +static __always_inline const char *step_into(struct nameidata *nd, int flags, + struct dentry *dentry) +{ + /* + * In the common case we are in rcu-walk and traversing over a non-mounted on + * directory (as opposed to e.g., a symlink). + * + * We can handle that and negative entries with the checks below. + */ + if (likely((nd->flags & LOOKUP_RCU) && + !d_managed(dentry) && !d_is_symlink(dentry))) { + struct inode *inode = dentry->d_inode; + if (read_seqcount_retry(&dentry->d_seq, nd->next_seq)) + return ERR_PTR(-ECHILD); + if (unlikely(!inode)) + return ERR_PTR(-ENOENT); + nd->path.dentry = dentry; + /* nd->path.mnt remains unchanged as no mount point was crossed */ + nd->inode = inode; + nd->seq = nd->next_seq; + return NULL; + } + return step_into_slowpath(nd, flags, dentry); +} + +static struct dentry *follow_dotdot_rcu(struct nameidata *nd) +{ + struct dentry *parent, *old; + + if (path_equal(&nd->path, &nd->root)) + goto in_root; + if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) { + struct path path; + unsigned seq; + if (!choose_mountpoint_rcu(real_mount(nd->path.mnt), + &nd->root, &path, &seq)) + goto in_root; + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) + return ERR_PTR(-ECHILD); + nd->path = path; + nd->inode = path.dentry->d_inode; + nd->seq = seq; + // makes sure that non-RCU pathwalk could reach this state + if (read_seqretry(&mount_lock, nd->m_seq)) + return ERR_PTR(-ECHILD); + /* we know that mountpoint was pinned */ + } + old = nd->path.dentry; + parent = old->d_parent; + nd->next_seq = read_seqcount_begin(&parent->d_seq); + // makes sure that non-RCU pathwalk could reach this state + if (read_seqcount_retry(&old->d_seq, nd->seq)) + return ERR_PTR(-ECHILD); + if (unlikely(!path_connected(nd->path.mnt, parent))) + return ERR_PTR(-ECHILD); + return parent; +in_root: + if (read_seqretry(&mount_lock, nd->m_seq)) + return ERR_PTR(-ECHILD); + if (unlikely(nd->flags & LOOKUP_BENEATH)) + return ERR_PTR(-ECHILD); + nd->next_seq = nd->seq; + return nd->path.dentry; +} + +static struct dentry *follow_dotdot(struct nameidata *nd) +{ + struct dentry *parent; + + if (path_equal(&nd->path, &nd->root)) + goto in_root; + if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) { + struct path path; + + if (!choose_mountpoint(real_mount(nd->path.mnt), + &nd->root, &path)) + goto in_root; + path_put(&nd->path); + nd->path = path; + nd->inode = path.dentry->d_inode; + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) + return ERR_PTR(-EXDEV); + } + /* rare case of legitimate dget_parent()... */ + parent = dget_parent(nd->path.dentry); + if (unlikely(!path_connected(nd->path.mnt, parent))) { + dput(parent); + return ERR_PTR(-ENOENT); + } + return parent; + +in_root: + if (unlikely(nd->flags & LOOKUP_BENEATH)) + return ERR_PTR(-EXDEV); + return dget(nd->path.dentry); +} + +static const char *handle_dots(struct nameidata *nd, enum last_type type) +{ + if (type == LAST_DOTDOT) { + const char *error = NULL; + struct dentry *parent; + + if (!nd->root.mnt) { + error = ERR_PTR(set_root(nd)); + if (unlikely(error)) + return error; + } + if (nd->flags & LOOKUP_RCU) + parent = follow_dotdot_rcu(nd); + else + parent = follow_dotdot(nd); + if (IS_ERR(parent)) + return ERR_CAST(parent); + error = step_into(nd, WALK_NOFOLLOW, parent); + if (unlikely(error)) + return error; + + if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) { + /* + * If there was a racing rename or mount along our + * path, then we can't be sure that ".." hasn't jumped + * above nd->root (and so userspace should retry or use + * some fallback). + */ + smp_rmb(); + if (__read_seqcount_retry(&mount_lock.seqcount, nd->m_seq)) + return ERR_PTR(-EAGAIN); + if (__read_seqcount_retry(&rename_lock.seqcount, nd->r_seq)) + return ERR_PTR(-EAGAIN); + } + } + return NULL; +} + +static __always_inline const char *walk_component(struct nameidata *nd, int flags) +{ + struct dentry *dentry; + /* + * "." and ".." are special - ".." especially so because it has + * to be able to know about the current root directory and + * parent relationships. + */ + if (unlikely(nd->last_type != LAST_NORM)) { + if (unlikely(nd->depth) && !(flags & WALK_MORE)) + put_link(nd); + return handle_dots(nd, nd->last_type); + } + dentry = lookup_fast(nd); + if (IS_ERR(dentry)) + return ERR_CAST(dentry); + if (unlikely(!dentry)) { + dentry = lookup_slow(&nd->last, nd->path.dentry, nd->flags); + if (IS_ERR(dentry)) + return ERR_CAST(dentry); + } + if (unlikely(nd->depth) && !(flags & WALK_MORE)) + put_link(nd); + return step_into(nd, flags, dentry); +} + +/* + * We can do the critical dentry name comparison and hashing + * operations one word at a time, but we are limited to: + * + * - Architectures with fast unaligned word accesses. We could + * do a "get_unaligned()" if this helps and is sufficiently + * fast. + * + * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we + * do not trap on the (extremely unlikely) case of a page + * crossing operation. + * + * - Furthermore, we need an efficient 64-bit compile for the + * 64-bit case in order to generate the "number of bytes in + * the final mask". Again, that could be replaced with a + * efficient population count instruction or similar. + */ +#ifdef CONFIG_DCACHE_WORD_ACCESS + +#include <asm/word-at-a-time.h> + +#ifdef HASH_MIX + +/* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */ + +#elif defined(CONFIG_64BIT) +/* + * Register pressure in the mixing function is an issue, particularly + * on 32-bit x86, but almost any function requires one state value and + * one temporary. Instead, use a function designed for two state values + * and no temporaries. + * + * This function cannot create a collision in only two iterations, so + * we have two iterations to achieve avalanche. In those two iterations, + * we have six layers of mixing, which is enough to spread one bit's + * influence out to 2^6 = 64 state bits. + * + * Rotate constants are scored by considering either 64 one-bit input + * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the + * probability of that delta causing a change to each of the 128 output + * bits, using a sample of random initial states. + * + * The Shannon entropy of the computed probabilities is then summed + * to produce a score. Ideally, any input change has a 50% chance of + * toggling any given output bit. + * + * Mixing scores (in bits) for (12,45): + * Input delta: 1-bit 2-bit + * 1 round: 713.3 42542.6 + * 2 rounds: 2753.7 140389.8 + * 3 rounds: 5954.1 233458.2 + * 4 rounds: 7862.6 256672.2 + * Perfect: 8192 258048 + * (64*128) (64*63/2 * 128) + */ +#define HASH_MIX(x, y, a) \ + ( x ^= (a), \ + y ^= x, x = rol64(x,12),\ + x += y, y = rol64(y,45),\ + y *= 9 ) + +/* + * Fold two longs into one 32-bit hash value. This must be fast, but + * latency isn't quite as critical, as there is a fair bit of additional + * work done before the hash value is used. + */ +static inline unsigned int fold_hash(unsigned long x, unsigned long y) +{ + y ^= x * GOLDEN_RATIO_64; + y *= GOLDEN_RATIO_64; + return y >> 32; +} + +#else /* 32-bit case */ + +/* + * Mixing scores (in bits) for (7,20): + * Input delta: 1-bit 2-bit + * 1 round: 330.3 9201.6 + * 2 rounds: 1246.4 25475.4 + * 3 rounds: 1907.1 31295.1 + * 4 rounds: 2042.3 31718.6 + * Perfect: 2048 31744 + * (32*64) (32*31/2 * 64) + */ +#define HASH_MIX(x, y, a) \ + ( x ^= (a), \ + y ^= x, x = rol32(x, 7),\ + x += y, y = rol32(y,20),\ + y *= 9 ) + +static inline unsigned int fold_hash(unsigned long x, unsigned long y) +{ + /* Use arch-optimized multiply if one exists */ + return __hash_32(y ^ __hash_32(x)); +} + +#endif + +/* + * Return the hash of a string of known length. This is carfully + * designed to match hash_name(), which is the more critical function. + * In particular, we must end by hashing a final word containing 0..7 + * payload bytes, to match the way that hash_name() iterates until it + * finds the delimiter after the name. + */ +unsigned int full_name_hash(const void *salt, const char *name, unsigned int len) +{ + unsigned long a, x = 0, y = (unsigned long)salt; + + for (;;) { + if (!len) + goto done; + a = load_unaligned_zeropad(name); + if (len < sizeof(unsigned long)) + break; + HASH_MIX(x, y, a); + name += sizeof(unsigned long); + len -= sizeof(unsigned long); + } + x ^= a & bytemask_from_count(len); +done: + return fold_hash(x, y); +} +EXPORT_SYMBOL(full_name_hash); + +/* Return the "hash_len" (hash and length) of a null-terminated string */ +u64 hashlen_string(const void *salt, const char *name) +{ + unsigned long a = 0, x = 0, y = (unsigned long)salt; + unsigned long adata, mask, len; + const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; + + len = 0; + goto inside; + + do { + HASH_MIX(x, y, a); + len += sizeof(unsigned long); +inside: + a = load_unaligned_zeropad(name+len); + } while (!has_zero(a, &adata, &constants)); + + adata = prep_zero_mask(a, adata, &constants); + mask = create_zero_mask(adata); + x ^= a & zero_bytemask(mask); + + return hashlen_create(fold_hash(x, y), len + find_zero(mask)); +} +EXPORT_SYMBOL(hashlen_string); + +/* + * hash_name - Calculate the length and hash of the path component + * @nd: the path resolution state + * @name: the pathname to read the component from + * @lastword: if the component fits in a single word, LAST_WORD_IS_DOT, + * LAST_WORD_IS_DOTDOT, or some other value depending on whether the + * component is '.', '..', or something else. Otherwise, @lastword is 0. + * + * Returns: a pointer to the terminating '/' or NUL character in @name. + */ +static inline const char *hash_name(struct nameidata *nd, + const char *name, + unsigned long *lastword) +{ + unsigned long a, b, x, y = (unsigned long)nd->path.dentry; + unsigned long adata, bdata, mask, len; + const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; + + /* + * The first iteration is special, because it can result in + * '.' and '..' and has no mixing other than the final fold. + */ + a = load_unaligned_zeropad(name); + b = a ^ REPEAT_BYTE('/'); + if (has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)) { + adata = prep_zero_mask(a, adata, &constants); + bdata = prep_zero_mask(b, bdata, &constants); + mask = create_zero_mask(adata | bdata); + a &= zero_bytemask(mask); + *lastword = a; + len = find_zero(mask); + nd->last.hash = fold_hash(a, y); + nd->last.len = len; + return name + len; + } + + len = 0; + x = 0; + do { + HASH_MIX(x, y, a); + len += sizeof(unsigned long); + a = load_unaligned_zeropad(name+len); + b = a ^ REPEAT_BYTE('/'); + } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants))); + + adata = prep_zero_mask(a, adata, &constants); + bdata = prep_zero_mask(b, bdata, &constants); + mask = create_zero_mask(adata | bdata); + a &= zero_bytemask(mask); + x ^= a; + len += find_zero(mask); + *lastword = 0; // Multi-word components cannot be DOT or DOTDOT + + nd->last.hash = fold_hash(x, y); + nd->last.len = len; + return name + len; +} + +/* + * Note that the 'last' word is always zero-masked, but + * was loaded as a possibly big-endian word. + */ +#ifdef __BIG_ENDIAN + #define LAST_WORD_IS_DOT (0x2eul << (BITS_PER_LONG-8)) + #define LAST_WORD_IS_DOTDOT (0x2e2eul << (BITS_PER_LONG-16)) +#endif + +#else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */ + +/* Return the hash of a string of known length */ +unsigned int full_name_hash(const void *salt, const char *name, unsigned int len) +{ + unsigned long hash = init_name_hash(salt); + while (len--) + hash = partial_name_hash((unsigned char)*name++, hash); + return end_name_hash(hash); +} +EXPORT_SYMBOL(full_name_hash); + +/* Return the "hash_len" (hash and length) of a null-terminated string */ +u64 hashlen_string(const void *salt, const char *name) +{ + unsigned long hash = init_name_hash(salt); + unsigned long len = 0, c; + + c = (unsigned char)*name; + while (c) { + len++; + hash = partial_name_hash(c, hash); + c = (unsigned char)name[len]; + } + return hashlen_create(end_name_hash(hash), len); +} +EXPORT_SYMBOL(hashlen_string); + +/* + * We know there's a real path component here of at least + * one character. + */ +static inline const char *hash_name(struct nameidata *nd, const char *name, unsigned long *lastword) +{ + unsigned long hash = init_name_hash(nd->path.dentry); + unsigned long len = 0, c, last = 0; + + c = (unsigned char)*name; + do { + last = (last << 8) + c; + len++; + hash = partial_name_hash(c, hash); + c = (unsigned char)name[len]; + } while (c && c != '/'); + + // This is reliable for DOT or DOTDOT, since the component + // cannot contain NUL characters - top bits being zero means + // we cannot have had any other pathnames. + *lastword = last; + nd->last.hash = end_name_hash(hash); + nd->last.len = len; + return name + len; +} + +#endif + +#ifndef LAST_WORD_IS_DOT + #define LAST_WORD_IS_DOT 0x2e + #define LAST_WORD_IS_DOTDOT 0x2e2e +#endif + +/* + * Name resolution. + * This is the basic name resolution function, turning a pathname into + * the final dentry. We expect 'base' to be positive and a directory. + * + * Returns 0 and nd will have valid dentry and mnt on success. + * Returns error and drops reference to input namei data on failure. + */ +static int link_path_walk(const char *name, struct nameidata *nd) +{ + int depth = 0; // depth <= nd->depth + int err; + + nd->last_type = LAST_ROOT; + nd->flags |= LOOKUP_PARENT; + if (IS_ERR(name)) + return PTR_ERR(name); + if (*name == '/') { + do { + name++; + } while (unlikely(*name == '/')); + } + if (unlikely(!*name)) { + nd->dir_mode = 0; // short-circuit the 'hardening' idiocy + return 0; + } + + /* At this point we know we have a real path component. */ + for(;;) { + struct mnt_idmap *idmap; + const char *link; + unsigned long lastword; + + idmap = mnt_idmap(nd->path.mnt); + err = may_lookup(idmap, nd); + if (unlikely(err)) + return err; + + nd->last.name = name; + name = hash_name(nd, name, &lastword); + + switch(lastword) { + case LAST_WORD_IS_DOTDOT: + nd->last_type = LAST_DOTDOT; + nd->state |= ND_JUMPED; + break; + + case LAST_WORD_IS_DOT: + nd->last_type = LAST_DOT; + break; + + default: + nd->last_type = LAST_NORM; + nd->state &= ~ND_JUMPED; + + struct dentry *parent = nd->path.dentry; + if (unlikely(parent->d_flags & DCACHE_OP_HASH)) { + err = parent->d_op->d_hash(parent, &nd->last); + if (err < 0) + return err; + } + } + + if (!*name) + goto OK; + /* + * If it wasn't NUL, we know it was '/'. Skip that + * slash, and continue until no more slashes. + */ + do { + name++; + } while (unlikely(*name == '/')); + if (unlikely(!*name)) { +OK: + /* pathname or trailing symlink, done */ + if (likely(!depth)) { + nd->dir_vfsuid = i_uid_into_vfsuid(idmap, nd->inode); + nd->dir_mode = nd->inode->i_mode; + nd->flags &= ~LOOKUP_PARENT; + return 0; + } + /* last component of nested symlink */ + name = nd->stack[--depth].name; + link = walk_component(nd, 0); + } else { + /* not the last component */ + link = walk_component(nd, WALK_MORE); + } + if (unlikely(link)) { + if (IS_ERR(link)) + return PTR_ERR(link); + /* a symlink to follow */ + nd->stack[depth++].name = name; + name = link; + continue; + } + if (unlikely(!d_can_lookup(nd->path.dentry))) { + if (nd->flags & LOOKUP_RCU) { + if (!try_to_unlazy(nd)) + return -ECHILD; + } + return -ENOTDIR; + } + } +} + +/* must be paired with terminate_walk() */ +static const char *path_init(struct nameidata *nd, unsigned flags) +{ + int error; + const char *s = nd->pathname; + + /* LOOKUP_CACHED requires RCU, ask caller to retry */ + if (unlikely((flags & (LOOKUP_RCU | LOOKUP_CACHED)) == LOOKUP_CACHED)) + return ERR_PTR(-EAGAIN); + + if (unlikely(!*s)) + flags &= ~LOOKUP_RCU; + if (flags & LOOKUP_RCU) + rcu_read_lock(); + else + nd->seq = nd->next_seq = 0; + + nd->flags = flags; + nd->state |= ND_JUMPED; + + nd->m_seq = __read_seqcount_begin(&mount_lock.seqcount); + nd->r_seq = __read_seqcount_begin(&rename_lock.seqcount); + smp_rmb(); + + if (unlikely(nd->state & ND_ROOT_PRESET)) { + struct dentry *root = nd->root.dentry; + struct inode *inode = root->d_inode; + if (*s && unlikely(!d_can_lookup(root))) + return ERR_PTR(-ENOTDIR); + nd->path = nd->root; + nd->inode = inode; + if (flags & LOOKUP_RCU) { + nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); + nd->root_seq = nd->seq; + } else { + path_get(&nd->path); + } + return s; + } + + nd->root.mnt = NULL; + + /* Absolute pathname -- fetch the root (LOOKUP_IN_ROOT uses nd->dfd). */ + if (*s == '/' && likely(!(flags & LOOKUP_IN_ROOT))) { + error = nd_jump_root(nd); + if (unlikely(error)) + return ERR_PTR(error); + return s; + } + + /* Relative pathname -- get the starting-point it is relative to. */ + if (nd->dfd == AT_FDCWD) { + if (flags & LOOKUP_RCU) { + struct fs_struct *fs = current->fs; + unsigned seq; + + do { + seq = read_seqbegin(&fs->seq); + nd->path = fs->pwd; + nd->inode = nd->path.dentry->d_inode; + nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); + } while (read_seqretry(&fs->seq, seq)); + } else { + get_fs_pwd(current->fs, &nd->path); + nd->inode = nd->path.dentry->d_inode; + } + } else { + /* Caller must check execute permissions on the starting path component */ + CLASS(fd_raw, f)(nd->dfd); + struct dentry *dentry; + + if (fd_empty(f)) + return ERR_PTR(-EBADF); + + if (flags & LOOKUP_LINKAT_EMPTY) { + if (fd_file(f)->f_cred != current_cred() && + !ns_capable(fd_file(f)->f_cred->user_ns, CAP_DAC_READ_SEARCH)) + return ERR_PTR(-ENOENT); + } + + dentry = fd_file(f)->f_path.dentry; + + if (*s && unlikely(!d_can_lookup(dentry))) + return ERR_PTR(-ENOTDIR); + + nd->path = fd_file(f)->f_path; + if (flags & LOOKUP_RCU) { + nd->inode = nd->path.dentry->d_inode; + nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); + } else { + path_get(&nd->path); + nd->inode = nd->path.dentry->d_inode; + } + } + + /* For scoped-lookups we need to set the root to the dirfd as well. */ + if (unlikely(flags & LOOKUP_IS_SCOPED)) { + nd->root = nd->path; + if (flags & LOOKUP_RCU) { + nd->root_seq = nd->seq; + } else { + path_get(&nd->root); + nd->state |= ND_ROOT_GRABBED; + } + } + return s; +} + +static inline const char *lookup_last(struct nameidata *nd) +{ + if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) + nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; + + return walk_component(nd, WALK_TRAILING); +} + +static int handle_lookup_down(struct nameidata *nd) +{ + if (!(nd->flags & LOOKUP_RCU)) + dget(nd->path.dentry); + nd->next_seq = nd->seq; + return PTR_ERR(step_into(nd, WALK_NOFOLLOW, nd->path.dentry)); +} + +/* Returns 0 and nd will be valid on success; Returns error, otherwise. */ +static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path) +{ + const char *s = path_init(nd, flags); + int err; + + if (unlikely(flags & LOOKUP_DOWN) && !IS_ERR(s)) { + err = handle_lookup_down(nd); + if (unlikely(err < 0)) + s = ERR_PTR(err); + } + + while (!(err = link_path_walk(s, nd)) && + (s = lookup_last(nd)) != NULL) + ; + if (!err && unlikely(nd->flags & LOOKUP_MOUNTPOINT)) { + err = handle_lookup_down(nd); + nd->state &= ~ND_JUMPED; // no d_weak_revalidate(), please... + } + if (!err) + err = complete_walk(nd); + + if (!err && nd->flags & LOOKUP_DIRECTORY) + if (!d_can_lookup(nd->path.dentry)) + err = -ENOTDIR; + if (!err) { + *path = nd->path; + nd->path.mnt = NULL; + nd->path.dentry = NULL; + } + terminate_walk(nd); + return err; +} + +int filename_lookup(int dfd, struct filename *name, unsigned flags, + struct path *path, const struct path *root) +{ + int retval; + struct nameidata nd; + if (IS_ERR(name)) + return PTR_ERR(name); + set_nameidata(&nd, dfd, name, root); + retval = path_lookupat(&nd, flags | LOOKUP_RCU, path); + if (unlikely(retval == -ECHILD)) + retval = path_lookupat(&nd, flags, path); + if (unlikely(retval == -ESTALE)) + retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path); + + if (likely(!retval)) + audit_inode(name, path->dentry, + flags & LOOKUP_MOUNTPOINT ? AUDIT_INODE_NOEVAL : 0); + restore_nameidata(); + return retval; +} + +/* Returns 0 and nd will be valid on success; Returns error, otherwise. */ +static int path_parentat(struct nameidata *nd, unsigned flags, + struct path *parent) +{ + const char *s = path_init(nd, flags); + int err = link_path_walk(s, nd); + if (!err) + err = complete_walk(nd); + if (!err) { + *parent = nd->path; + nd->path.mnt = NULL; + nd->path.dentry = NULL; + } + terminate_walk(nd); + return err; +} + +/* Note: this does not consume "name" */ +static int __filename_parentat(int dfd, struct filename *name, + unsigned int flags, struct path *parent, + struct qstr *last, enum last_type *type, + const struct path *root) +{ + int retval; + struct nameidata nd; + + if (IS_ERR(name)) + return PTR_ERR(name); + set_nameidata(&nd, dfd, name, root); + retval = path_parentat(&nd, flags | LOOKUP_RCU, parent); + if (unlikely(retval == -ECHILD)) + retval = path_parentat(&nd, flags, parent); + if (unlikely(retval == -ESTALE)) + retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent); + if (likely(!retval)) { + *last = nd.last; + *type = nd.last_type; + audit_inode(name, parent->dentry, AUDIT_INODE_PARENT); + } + restore_nameidata(); + return retval; +} + +static int filename_parentat(int dfd, struct filename *name, + unsigned int flags, struct path *parent, + struct qstr *last, enum last_type *type) +{ + return __filename_parentat(dfd, name, flags, parent, last, type, NULL); +} + +static struct dentry *__start_dirop(struct dentry *parent, struct qstr *name, + unsigned int lookup_flags, + unsigned int state) +{ + struct dentry *dentry; + struct inode *dir = d_inode(parent); + + if (state == TASK_KILLABLE) { + int ret = down_write_killable_nested(&dir->i_rwsem, + I_MUTEX_PARENT); + if (ret) + return ERR_PTR(ret); + } else { + inode_lock_nested(dir, I_MUTEX_PARENT); + } + dentry = lookup_one_qstr_excl(name, parent, lookup_flags); + if (IS_ERR(dentry)) + inode_unlock(dir); + return dentry; +} + +/** + * start_dirop - begin a create or remove dirop, performing locking and lookup + * @parent: the dentry of the parent in which the operation will occur + * @name: a qstr holding the name within that parent + * @lookup_flags: intent and other lookup flags. + * + * The lookup is performed and necessary locks are taken so that, on success, + * the returned dentry can be operated on safely. + * The qstr must already have the hash value calculated. + * + * Returns: a locked dentry, or an error. + * + */ +struct dentry *start_dirop(struct dentry *parent, struct qstr *name, + unsigned int lookup_flags) +{ + return __start_dirop(parent, name, lookup_flags, TASK_NORMAL); +} + +/** + * end_dirop - signal completion of a dirop + * @de: the dentry which was returned by start_dirop or similar. + * + * If the de is an error, nothing happens. Otherwise any lock taken to + * protect the dentry is dropped and the dentry itself is release (dput()). + */ +void end_dirop(struct dentry *de) +{ + if (!IS_ERR(de)) { + inode_unlock(de->d_parent->d_inode); + dput(de); + } +} +EXPORT_SYMBOL(end_dirop); + +/* does lookup, returns the object with parent locked */ +struct dentry *start_removing_path(const char *name, struct path *path) +{ + CLASS(filename_kernel, filename)(name); + struct path parent_path __free(path_put) = {}; + struct dentry *d; + struct qstr last; + enum last_type type; + int error; + + error = filename_parentat(AT_FDCWD, filename, 0, &parent_path, &last, + &type); + if (error) + return ERR_PTR(error); + if (unlikely(type != LAST_NORM)) + return ERR_PTR(-EINVAL); + /* don't fail immediately if it's r/o, at least try to report other errors */ + error = mnt_want_write(parent_path.mnt); + d = start_dirop(parent_path.dentry, &last, 0); + if (IS_ERR(d)) + goto drop; + if (error) + goto fail; + path->dentry = no_free_ptr(parent_path.dentry); + path->mnt = no_free_ptr(parent_path.mnt); + return d; + +fail: + end_dirop(d); + d = ERR_PTR(error); +drop: + if (!error) + mnt_drop_write(parent_path.mnt); + return d; +} + +/** + * kern_path_parent: lookup path returning parent and target + * @name: path name + * @path: path to store parent in + * + * The path @name should end with a normal component, not "." or ".." or "/". + * A lookup is performed and if successful the parent information + * is store in @parent and the dentry is returned. + * + * The dentry maybe negative, the parent will be positive. + * + * Returns: dentry or error. + */ +struct dentry *kern_path_parent(const char *name, struct path *path) +{ + struct path parent_path __free(path_put) = {}; + CLASS(filename_kernel, filename)(name); + struct dentry *d; + struct qstr last; + enum last_type type; + int error; + + error = filename_parentat(AT_FDCWD, filename, 0, &parent_path, &last, &type); + if (error) + return ERR_PTR(error); + if (unlikely(type != LAST_NORM)) + return ERR_PTR(-EINVAL); + + d = lookup_noperm_unlocked(&last, parent_path.dentry); + if (IS_ERR(d)) + return d; + path->dentry = no_free_ptr(parent_path.dentry); + path->mnt = no_free_ptr(parent_path.mnt); + return d; +} + +int kern_path(const char *name, unsigned int flags, struct path *path) +{ + CLASS(filename_kernel, filename)(name); + return filename_lookup(AT_FDCWD, filename, flags, path, NULL); +} +EXPORT_SYMBOL(kern_path); + +/** + * vfs_path_parent_lookup - lookup a parent path relative to a dentry-vfsmount pair + * @filename: filename structure + * @flags: lookup flags + * @parent: pointer to struct path to fill + * @last: last component + * @root: pointer to struct path of the base directory + */ +int vfs_path_parent_lookup(struct filename *filename, unsigned int flags, + struct path *parent, struct qstr *last, + const struct path *root) +{ + enum last_type type; + int err = __filename_parentat(AT_FDCWD, filename, flags, parent, last, + &type, root); + if (err) + return err; + if (unlikely(type != LAST_NORM)) { + path_put(parent); + return -EINVAL; + } + return 0; +} +EXPORT_SYMBOL(vfs_path_parent_lookup); + +/** + * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair + * @dentry: pointer to dentry of the base directory + * @mnt: pointer to vfs mount of the base directory + * @name: pointer to file name + * @flags: lookup flags + * @path: pointer to struct path to fill + */ +int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, + const char *name, unsigned int flags, + struct path *path) +{ + CLASS(filename_kernel, filename)(name); + struct path root = {.mnt = mnt, .dentry = dentry}; + + /* the first argument of filename_lookup() is ignored with root */ + return filename_lookup(AT_FDCWD, filename, flags, path, &root); +} +EXPORT_SYMBOL(vfs_path_lookup); + +int lookup_noperm_common(struct qstr *qname, struct dentry *base) +{ + const char *name = qname->name; + u32 len = qname->len; + + qname->hash = full_name_hash(base, name, len); + if (!len) + return -EACCES; + + if (name_is_dot_dotdot(name, len)) + return -EACCES; + + while (len--) { + unsigned int c = *(const unsigned char *)name++; + if (c == '/' || c == '\0') + return -EACCES; + } + /* + * See if the low-level filesystem might want + * to use its own hash.. + */ + if (base->d_flags & DCACHE_OP_HASH) { + int err = base->d_op->d_hash(base, qname); + if (err < 0) + return err; + } + return 0; +} + +static int lookup_one_common(struct mnt_idmap *idmap, + struct qstr *qname, struct dentry *base) +{ + int err; + err = lookup_noperm_common(qname, base); + if (err < 0) + return err; + return inode_permission(idmap, base->d_inode, MAY_EXEC); +} + +/** + * try_lookup_noperm - filesystem helper to lookup single pathname component + * @name: qstr storing pathname component to lookup + * @base: base directory to lookup from + * + * Look up a dentry by name in the dcache, returning NULL if it does not + * currently exist or an error if there is a problem with the name. + * The function does not try to create a dentry and if one + * is found it doesn't try to revalidate it. + * + * Note that this routine is purely a helper for filesystem usage and should + * not be called by generic code. It does no permission checking. + * + * No locks need be held - only a counted reference to @base is needed. + * + * Returns: + * - ref-counted dentry on success, or + * - %NULL if name could not be found, or + * - ERR_PTR(-EACCES) if name is dot or dotdot or contains a slash or nul, or + * - ERR_PTR() if fs provide ->d_hash, and this returned an error. + */ +struct dentry *try_lookup_noperm(struct qstr *name, struct dentry *base) +{ + int err; + + err = lookup_noperm_common(name, base); + if (err) + return ERR_PTR(err); + + return d_lookup(base, name); +} +EXPORT_SYMBOL(try_lookup_noperm); + +/** + * lookup_noperm - filesystem helper to lookup single pathname component + * @name: qstr storing pathname component to lookup + * @base: base directory to lookup from + * + * Note that this routine is purely a helper for filesystem usage and should + * not be called by generic code. It does no permission checking. + * + * The caller must hold base->i_rwsem. + */ +struct dentry *lookup_noperm(struct qstr *name, struct dentry *base) +{ + struct dentry *dentry; + int err; + + WARN_ON_ONCE(!inode_is_locked(base->d_inode)); + + err = lookup_noperm_common(name, base); + if (err) + return ERR_PTR(err); + + dentry = lookup_dcache(name, base, 0); + return dentry ? dentry : __lookup_slow(name, base, 0); +} +EXPORT_SYMBOL(lookup_noperm); + +/** + * lookup_one - lookup single pathname component + * @idmap: idmap of the mount the lookup is performed from + * @name: qstr holding pathname component to lookup + * @base: base directory to lookup from + * + * This can be used for in-kernel filesystem clients such as file servers. + * + * The caller must hold base->i_rwsem. + */ +struct dentry *lookup_one(struct mnt_idmap *idmap, struct qstr *name, + struct dentry *base) +{ + struct dentry *dentry; + int err; + + WARN_ON_ONCE(!inode_is_locked(base->d_inode)); + + err = lookup_one_common(idmap, name, base); + if (err) + return ERR_PTR(err); + + dentry = lookup_dcache(name, base, 0); + return dentry ? dentry : __lookup_slow(name, base, 0); +} +EXPORT_SYMBOL(lookup_one); + +/** + * lookup_one_unlocked - lookup single pathname component + * @idmap: idmap of the mount the lookup is performed from + * @name: qstr olding pathname component to lookup + * @base: base directory to lookup from + * + * This can be used for in-kernel filesystem clients such as file servers. + * + * Unlike lookup_one, it should be called without the parent + * i_rwsem held, and will take the i_rwsem itself if necessary. + * + * Returns: - A dentry, possibly negative, or + * - same errors as try_lookup_noperm() or + * - ERR_PTR(-ENOENT) if parent has been removed, or + * - ERR_PTR(-EACCES) if parent directory is not searchable. + */ +struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap, struct qstr *name, + struct dentry *base) +{ + int err; + struct dentry *ret; + + err = lookup_one_common(idmap, name, base); + if (err) + return ERR_PTR(err); + + ret = lookup_dcache(name, base, 0); + if (!ret) + ret = lookup_slow(name, base, 0); + return ret; +} +EXPORT_SYMBOL(lookup_one_unlocked); + +/** + * lookup_one_positive_killable - lookup single pathname component + * @idmap: idmap of the mount the lookup is performed from + * @name: qstr olding pathname component to lookup + * @base: base directory to lookup from + * + * This helper will yield ERR_PTR(-ENOENT) on negatives. The helper returns + * known positive or ERR_PTR(). This is what most of the users want. + * + * Note that pinned negative with unlocked parent _can_ become positive at any + * time, so callers of lookup_one_unlocked() need to be very careful; pinned + * positives have >d_inode stable, so this one avoids such problems. + * + * This can be used for in-kernel filesystem clients such as file servers. + * + * It should be called without the parent i_rwsem held, and will take + * the i_rwsem itself if necessary. If a fatal signal is pending or + * delivered, it will return %-EINTR if the lock is needed. + * + * Returns: A dentry, possibly negative, or + * - same errors as lookup_one_unlocked() or + * - ERR_PTR(-EINTR) if a fatal signal is pending. + */ +struct dentry *lookup_one_positive_killable(struct mnt_idmap *idmap, + struct qstr *name, + struct dentry *base) +{ + int err; + struct dentry *ret; + + err = lookup_one_common(idmap, name, base); + if (err) + return ERR_PTR(err); + + ret = lookup_dcache(name, base, 0); + if (!ret) + ret = lookup_slow_killable(name, base, 0); + if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) { + dput(ret); + ret = ERR_PTR(-ENOENT); + } + return ret; +} +EXPORT_SYMBOL(lookup_one_positive_killable); + +/** + * lookup_one_positive_unlocked - lookup single pathname component + * @idmap: idmap of the mount the lookup is performed from + * @name: qstr holding pathname component to lookup + * @base: base directory to lookup from + * + * This helper will yield ERR_PTR(-ENOENT) on negatives. The helper returns + * known positive or ERR_PTR(). This is what most of the users want. + * + * Note that pinned negative with unlocked parent _can_ become positive at any + * time, so callers of lookup_one_unlocked() need to be very careful; pinned + * positives have >d_inode stable, so this one avoids such problems. + * + * This can be used for in-kernel filesystem clients such as file servers. + * + * The helper should be called without i_rwsem held. + * + * Returns: A positive dentry, or + * - ERR_PTR(-ENOENT) if the name could not be found, or + * - same errors as lookup_one_unlocked(). + */ +struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap, + struct qstr *name, + struct dentry *base) +{ + struct dentry *ret = lookup_one_unlocked(idmap, name, base); + + if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) { + dput(ret); + ret = ERR_PTR(-ENOENT); + } + return ret; +} +EXPORT_SYMBOL(lookup_one_positive_unlocked); + +/** + * lookup_noperm_unlocked - filesystem helper to lookup single pathname component + * @name: pathname component to lookup + * @base: base directory to lookup from + * + * Note that this routine is purely a helper for filesystem usage and should + * not be called by generic code. It does no permission checking. + * + * Unlike lookup_noperm(), it should be called without the parent + * i_rwsem held, and will take the i_rwsem itself if necessary. + * + * Unlike try_lookup_noperm() it *does* revalidate the dentry if it already + * existed. + * + * Returns: A dentry, possibly negative, or + * - ERR_PTR(-ENOENT) if parent has been removed, or + * - same errors as try_lookup_noperm() + */ +struct dentry *lookup_noperm_unlocked(struct qstr *name, struct dentry *base) +{ + struct dentry *ret; + int err; + + err = lookup_noperm_common(name, base); + if (err) + return ERR_PTR(err); + + ret = lookup_dcache(name, base, 0); + if (!ret) + ret = lookup_slow(name, base, 0); + return ret; +} +EXPORT_SYMBOL(lookup_noperm_unlocked); + +/* + * Like lookup_noperm_unlocked(), except that it yields ERR_PTR(-ENOENT) + * on negatives. Returns known positive or ERR_PTR(); that's what + * most of the users want. Note that pinned negative with unlocked parent + * _can_ become positive at any time, so callers of lookup_noperm_unlocked() + * need to be very careful; pinned positives have ->d_inode stable, so + * this one avoids such problems. + * + * Returns: A positive dentry, or + * - ERR_PTR(-ENOENT) if name cannot be found or parent has been removed, or + * - same errors as try_lookup_noperm() + */ +struct dentry *lookup_noperm_positive_unlocked(struct qstr *name, + struct dentry *base) +{ + struct dentry *ret; + + ret = lookup_noperm_unlocked(name, base); + if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) { + dput(ret); + ret = ERR_PTR(-ENOENT); + } + return ret; +} +EXPORT_SYMBOL(lookup_noperm_positive_unlocked); + +/** + * start_creating - prepare to create a given name with permission checking + * @idmap: idmap of the mount + * @parent: directory in which to prepare to create the name + * @name: the name to be created + * + * Locks are taken and a lookup is performed prior to creating + * an object in a directory. Permission checking (MAY_EXEC) is performed + * against @idmap. + * + * If the name already exists, a positive dentry is returned, so + * behaviour is similar to O_CREAT without O_EXCL, which doesn't fail + * with -EEXIST. + * + * Returns: a negative or positive dentry, or an error. + */ +struct dentry *start_creating(struct mnt_idmap *idmap, struct dentry *parent, + struct qstr *name) +{ + int err = lookup_one_common(idmap, name, parent); + + if (err) + return ERR_PTR(err); + return start_dirop(parent, name, LOOKUP_CREATE); +} +EXPORT_SYMBOL(start_creating); + +/** + * start_removing - prepare to remove a given name with permission checking + * @idmap: idmap of the mount + * @parent: directory in which to find the name + * @name: the name to be removed + * + * Locks are taken and a lookup in performed prior to removing + * an object from a directory. Permission checking (MAY_EXEC) is performed + * against @idmap. + * + * If the name doesn't exist, an error is returned. + * + * end_removing() should be called when removal is complete, or aborted. + * + * Returns: a positive dentry, or an error. + */ +struct dentry *start_removing(struct mnt_idmap *idmap, struct dentry *parent, + struct qstr *name) +{ + int err = lookup_one_common(idmap, name, parent); + + if (err) + return ERR_PTR(err); + return start_dirop(parent, name, 0); +} +EXPORT_SYMBOL(start_removing); + +/** + * start_creating_killable - prepare to create a given name with permission checking + * @idmap: idmap of the mount + * @parent: directory in which to prepare to create the name + * @name: the name to be created + * + * Locks are taken and a lookup in performed prior to creating + * an object in a directory. Permission checking (MAY_EXEC) is performed + * against @idmap. + * + * If the name already exists, a positive dentry is returned. + * + * If a signal is received or was already pending, the function aborts + * with -EINTR; + * + * Returns: a negative or positive dentry, or an error. + */ +struct dentry *start_creating_killable(struct mnt_idmap *idmap, + struct dentry *parent, + struct qstr *name) +{ + int err = lookup_one_common(idmap, name, parent); + + if (err) + return ERR_PTR(err); + return __start_dirop(parent, name, LOOKUP_CREATE, TASK_KILLABLE); +} +EXPORT_SYMBOL(start_creating_killable); + +/** + * start_removing_killable - prepare to remove a given name with permission checking + * @idmap: idmap of the mount + * @parent: directory in which to find the name + * @name: the name to be removed + * + * Locks are taken and a lookup in performed prior to removing + * an object from a directory. Permission checking (MAY_EXEC) is performed + * against @idmap. + * + * If the name doesn't exist, an error is returned. + * + * end_removing() should be called when removal is complete, or aborted. + * + * If a signal is received or was already pending, the function aborts + * with -EINTR; + * + * Returns: a positive dentry, or an error. + */ +struct dentry *start_removing_killable(struct mnt_idmap *idmap, + struct dentry *parent, + struct qstr *name) +{ + int err = lookup_one_common(idmap, name, parent); + + if (err) + return ERR_PTR(err); + return __start_dirop(parent, name, 0, TASK_KILLABLE); +} +EXPORT_SYMBOL(start_removing_killable); + +/** + * start_creating_noperm - prepare to create a given name without permission checking + * @parent: directory in which to prepare to create the name + * @name: the name to be created + * + * Locks are taken and a lookup in performed prior to creating + * an object in a directory. + * + * If the name already exists, a positive dentry is returned. + * + * Returns: a negative or positive dentry, or an error. + */ +struct dentry *start_creating_noperm(struct dentry *parent, + struct qstr *name) +{ + int err = lookup_noperm_common(name, parent); + + if (err) + return ERR_PTR(err); + return start_dirop(parent, name, LOOKUP_CREATE); +} +EXPORT_SYMBOL(start_creating_noperm); + +/** + * start_removing_noperm - prepare to remove a given name without permission checking + * @parent: directory in which to find the name + * @name: the name to be removed + * + * Locks are taken and a lookup in performed prior to removing + * an object from a directory. + * + * If the name doesn't exist, an error is returned. + * + * end_removing() should be called when removal is complete, or aborted. + * + * Returns: a positive dentry, or an error. + */ +struct dentry *start_removing_noperm(struct dentry *parent, + struct qstr *name) +{ + int err = lookup_noperm_common(name, parent); + + if (err) + return ERR_PTR(err); + return start_dirop(parent, name, 0); +} +EXPORT_SYMBOL(start_removing_noperm); + +/** + * start_creating_dentry - prepare to create a given dentry + * @parent: directory from which dentry should be removed + * @child: the dentry to be removed + * + * A lock is taken to protect the dentry again other dirops and + * the validity of the dentry is checked: correct parent and still hashed. + * + * If the dentry is valid and negative a reference is taken and + * returned. If not an error is returned. + * + * end_creating() should be called when creation is complete, or aborted. + * + * Returns: the valid dentry, or an error. + */ +struct dentry *start_creating_dentry(struct dentry *parent, + struct dentry *child) +{ + inode_lock_nested(parent->d_inode, I_MUTEX_PARENT); + if (unlikely(IS_DEADDIR(parent->d_inode) || + child->d_parent != parent || + d_unhashed(child))) { + inode_unlock(parent->d_inode); + return ERR_PTR(-EINVAL); + } + if (d_is_positive(child)) { + inode_unlock(parent->d_inode); + return ERR_PTR(-EEXIST); + } + return dget(child); +} +EXPORT_SYMBOL(start_creating_dentry); + +/** + * start_removing_dentry - prepare to remove a given dentry + * @parent: directory from which dentry should be removed + * @child: the dentry to be removed + * + * A lock is taken to protect the dentry again other dirops and + * the validity of the dentry is checked: correct parent and still hashed. + * + * If the dentry is valid and positive, a reference is taken and + * returned. If not an error is returned. + * + * end_removing() should be called when removal is complete, or aborted. + * + * Returns: the valid dentry, or an error. + */ +struct dentry *start_removing_dentry(struct dentry *parent, + struct dentry *child) +{ + inode_lock_nested(parent->d_inode, I_MUTEX_PARENT); + if (unlikely(IS_DEADDIR(parent->d_inode) || + child->d_parent != parent || + d_unhashed(child))) { + inode_unlock(parent->d_inode); + return ERR_PTR(-EINVAL); + } + if (d_is_negative(child)) { + inode_unlock(parent->d_inode); + return ERR_PTR(-ENOENT); + } + return dget(child); +} +EXPORT_SYMBOL(start_removing_dentry); + +#ifdef CONFIG_UNIX98_PTYS +int path_pts(struct path *path) +{ + /* Find something mounted on "pts" in the same directory as + * the input path. + */ + struct dentry *parent = dget_parent(path->dentry); + struct dentry *child; + + if (unlikely(!path_connected(path->mnt, parent))) { + dput(parent); + return -ENOENT; + } + dput(path->dentry); + path->dentry = parent; + child = d_hash_and_lookup(parent, &QSTR("pts")); + if (IS_ERR_OR_NULL(child)) + return -ENOENT; + + path->dentry = child; + dput(parent); + follow_down(path, 0); + return 0; +} +#endif + +int user_path_at(int dfd, const char __user *name, unsigned flags, + struct path *path) +{ + CLASS(filename_flags, filename)(name, flags); + return filename_lookup(dfd, filename, flags, path, NULL); +} +EXPORT_SYMBOL(user_path_at); + +int __check_sticky(struct mnt_idmap *idmap, struct inode *dir, + struct inode *inode) +{ + kuid_t fsuid = current_fsuid(); + + if (vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), fsuid)) + return 0; + if (vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, dir), fsuid)) + return 0; + return !capable_wrt_inode_uidgid(idmap, inode, CAP_FOWNER); +} +EXPORT_SYMBOL(__check_sticky); + +/* + * Check whether we can remove a link victim from directory dir, check + * whether the type of victim is right. + * 1. We can't do it if dir is read-only (done in permission()) + * 2. We should have write and exec permissions on dir + * 3. We can't remove anything from append-only dir + * 4. We can't do anything with immutable dir (done in permission()) + * 5. If the sticky bit on dir is set we should either + * a. be owner of dir, or + * b. be owner of victim, or + * c. have CAP_FOWNER capability + * 6. If the victim is append-only or immutable we can't do antyhing with + * links pointing to it. + * 7. If the victim has an unknown uid or gid we can't change the inode. + * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR. + * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR. + * 10. We can't remove a root or mountpoint. + * 11. We don't allow removal of NFS sillyrenamed files; it's handled by + * nfs_async_unlink(). + */ +int may_delete_dentry(struct mnt_idmap *idmap, struct inode *dir, + struct dentry *victim, bool isdir) +{ + struct inode *inode = d_backing_inode(victim); + int error; + + if (d_is_negative(victim)) + return -ENOENT; + BUG_ON(!inode); + + BUG_ON(victim->d_parent->d_inode != dir); + + /* Inode writeback is not safe when the uid or gid are invalid. */ + if (!vfsuid_valid(i_uid_into_vfsuid(idmap, inode)) || + !vfsgid_valid(i_gid_into_vfsgid(idmap, inode))) + return -EOVERFLOW; + + audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE); + + error = inode_permission(idmap, dir, MAY_WRITE | MAY_EXEC); + if (error) + return error; + if (IS_APPEND(dir)) + return -EPERM; + + if (check_sticky(idmap, dir, inode) || IS_APPEND(inode) || + IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) || + HAS_UNMAPPED_ID(idmap, inode)) + return -EPERM; + if (isdir) { + if (!d_is_dir(victim)) + return -ENOTDIR; + if (IS_ROOT(victim)) + return -EBUSY; + } else if (d_is_dir(victim)) + return -EISDIR; + if (IS_DEADDIR(dir)) + return -ENOENT; + if (victim->d_flags & DCACHE_NFSFS_RENAMED) + return -EBUSY; + return 0; +} +EXPORT_SYMBOL(may_delete_dentry); + +/* Check whether we can create an object with dentry child in directory + * dir. + * 1. We can't do it if child already exists (open has special treatment for + * this case, but since we are inlined it's OK) + * 2. We can't do it if dir is read-only (done in permission()) + * 3. We can't do it if the fs can't represent the fsuid or fsgid. + * 4. We should have write and exec permissions on dir + * 5. We can't do it if dir is immutable (done in permission()) + */ +int may_create_dentry(struct mnt_idmap *idmap, + struct inode *dir, struct dentry *child) +{ + audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE); + if (child->d_inode) + return -EEXIST; + if (IS_DEADDIR(dir)) + return -ENOENT; + if (!fsuidgid_has_mapping(dir->i_sb, idmap)) + return -EOVERFLOW; + + return inode_permission(idmap, dir, MAY_WRITE | MAY_EXEC); +} +EXPORT_SYMBOL(may_create_dentry); + +// p1 != p2, both are on the same filesystem, ->s_vfs_rename_mutex is held +static struct dentry *lock_two_directories(struct dentry *p1, struct dentry *p2) +{ + struct dentry *p = p1, *q = p2, *r; + + while ((r = p->d_parent) != p2 && r != p) + p = r; + if (r == p2) { + // p is a child of p2 and an ancestor of p1 or p1 itself + inode_lock_nested(p2->d_inode, I_MUTEX_PARENT); + inode_lock_nested(p1->d_inode, I_MUTEX_PARENT2); + return p; + } + // p is the root of connected component that contains p1 + // p2 does not occur on the path from p to p1 + while ((r = q->d_parent) != p1 && r != p && r != q) + q = r; + if (r == p1) { + // q is a child of p1 and an ancestor of p2 or p2 itself + inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); + inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2); + return q; + } else if (likely(r == p)) { + // both p2 and p1 are descendents of p + inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); + inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2); + return NULL; + } else { // no common ancestor at the time we'd been called + mutex_unlock(&p1->d_sb->s_vfs_rename_mutex); + return ERR_PTR(-EXDEV); + } +} + +/* + * p1 and p2 should be directories on the same fs. + */ +static struct dentry *lock_rename(struct dentry *p1, struct dentry *p2) +{ + if (p1 == p2) { + inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); + return NULL; + } + + mutex_lock(&p1->d_sb->s_vfs_rename_mutex); + return lock_two_directories(p1, p2); +} + +/* + * c1 and p2 should be on the same fs. + */ +static struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2) +{ + if (READ_ONCE(c1->d_parent) == p2) { + /* + * hopefully won't need to touch ->s_vfs_rename_mutex at all. + */ + inode_lock_nested(p2->d_inode, I_MUTEX_PARENT); + /* + * now that p2 is locked, nobody can move in or out of it, + * so the test below is safe. + */ + if (likely(c1->d_parent == p2)) + return NULL; + + /* + * c1 got moved out of p2 while we'd been taking locks; + * unlock and fall back to slow case. + */ + inode_unlock(p2->d_inode); + } + + mutex_lock(&c1->d_sb->s_vfs_rename_mutex); + /* + * nobody can move out of any directories on this fs. + */ + if (likely(c1->d_parent != p2)) + return lock_two_directories(c1->d_parent, p2); + + /* + * c1 got moved into p2 while we were taking locks; + * we need p2 locked and ->s_vfs_rename_mutex unlocked, + * for consistency with lock_rename(). + */ + inode_lock_nested(p2->d_inode, I_MUTEX_PARENT); + mutex_unlock(&c1->d_sb->s_vfs_rename_mutex); + return NULL; +} + +static void unlock_rename(struct dentry *p1, struct dentry *p2) +{ + inode_unlock(p1->d_inode); + if (p1 != p2) { + inode_unlock(p2->d_inode); + mutex_unlock(&p1->d_sb->s_vfs_rename_mutex); + } +} + +/** + * __start_renaming - lookup and lock names for rename + * @rd: rename data containing parents and flags, and + * for receiving found dentries + * @lookup_flags: extra flags to pass to ->lookup (e.g. LOOKUP_REVAL, + * LOOKUP_NO_SYMLINKS etc). + * @old_last: name of object in @rd.old_parent + * @new_last: name of object in @rd.new_parent + * + * Look up two names and ensure locks are in place for + * rename. + * + * On success the found dentries are stored in @rd.old_dentry, + * @rd.new_dentry and an extra ref is taken on @rd.old_parent. + * These references and the lock are dropped by end_renaming(). + * + * The passed in qstrs must have the hash calculated, and no permission + * checking is performed. + * + * Returns: zero or an error. + */ +static int +__start_renaming(struct renamedata *rd, int lookup_flags, + struct qstr *old_last, struct qstr *new_last) +{ + struct dentry *trap; + struct dentry *d1, *d2; + int target_flags = LOOKUP_RENAME_TARGET | LOOKUP_CREATE; + int err; + + if (rd->flags & RENAME_EXCHANGE) + target_flags = 0; + if (rd->flags & RENAME_NOREPLACE) + target_flags |= LOOKUP_EXCL; + + trap = lock_rename(rd->old_parent, rd->new_parent); + if (IS_ERR(trap)) + return PTR_ERR(trap); + + d1 = lookup_one_qstr_excl(old_last, rd->old_parent, + lookup_flags); + err = PTR_ERR(d1); + if (IS_ERR(d1)) + goto out_unlock; + + d2 = lookup_one_qstr_excl(new_last, rd->new_parent, + lookup_flags | target_flags); + err = PTR_ERR(d2); + if (IS_ERR(d2)) + goto out_dput_d1; + + if (d1 == trap) { + /* source is an ancestor of target */ + err = -EINVAL; + goto out_dput_d2; + } + + if (d2 == trap) { + /* target is an ancestor of source */ + if (rd->flags & RENAME_EXCHANGE) + err = -EINVAL; + else + err = -ENOTEMPTY; + goto out_dput_d2; + } + + rd->old_dentry = d1; + rd->new_dentry = d2; + dget(rd->old_parent); + return 0; + +out_dput_d2: + dput(d2); +out_dput_d1: + dput(d1); +out_unlock: + unlock_rename(rd->old_parent, rd->new_parent); + return err; +} + +/** + * start_renaming - lookup and lock names for rename with permission checking + * @rd: rename data containing parents and flags, and + * for receiving found dentries + * @lookup_flags: extra flags to pass to ->lookup (e.g. LOOKUP_REVAL, + * LOOKUP_NO_SYMLINKS etc). + * @old_last: name of object in @rd.old_parent + * @new_last: name of object in @rd.new_parent + * + * Look up two names and ensure locks are in place for + * rename. + * + * On success the found dentries are stored in @rd.old_dentry, + * @rd.new_dentry. Also the refcount on @rd->old_parent is increased. + * These references and the lock are dropped by end_renaming(). + * + * The passed in qstrs need not have the hash calculated, and basic + * eXecute permission checking is performed against @rd.mnt_idmap. + * + * Returns: zero or an error. + */ +int start_renaming(struct renamedata *rd, int lookup_flags, + struct qstr *old_last, struct qstr *new_last) +{ + int err; + + err = lookup_one_common(rd->mnt_idmap, old_last, rd->old_parent); + if (err) + return err; + err = lookup_one_common(rd->mnt_idmap, new_last, rd->new_parent); + if (err) + return err; + return __start_renaming(rd, lookup_flags, old_last, new_last); +} +EXPORT_SYMBOL(start_renaming); + +static int +__start_renaming_dentry(struct renamedata *rd, int lookup_flags, + struct dentry *old_dentry, struct qstr *new_last) +{ + struct dentry *trap; + struct dentry *d2; + int target_flags = LOOKUP_RENAME_TARGET | LOOKUP_CREATE; + int err; + + if (rd->flags & RENAME_EXCHANGE) + target_flags = 0; + if (rd->flags & RENAME_NOREPLACE) + target_flags |= LOOKUP_EXCL; + + /* Already have the dentry - need to be sure to lock the correct parent */ + trap = lock_rename_child(old_dentry, rd->new_parent); + if (IS_ERR(trap)) + return PTR_ERR(trap); + if (d_unhashed(old_dentry) || + (rd->old_parent && rd->old_parent != old_dentry->d_parent)) { + /* dentry was removed, or moved and explicit parent requested */ + err = -EINVAL; + goto out_unlock; + } + + d2 = lookup_one_qstr_excl(new_last, rd->new_parent, + lookup_flags | target_flags); + err = PTR_ERR(d2); + if (IS_ERR(d2)) + goto out_unlock; + + if (old_dentry == trap) { + /* source is an ancestor of target */ + err = -EINVAL; + goto out_dput_d2; + } + + if (d2 == trap) { + /* target is an ancestor of source */ + if (rd->flags & RENAME_EXCHANGE) + err = -EINVAL; + else + err = -ENOTEMPTY; + goto out_dput_d2; + } + + rd->old_dentry = dget(old_dentry); + rd->new_dentry = d2; + rd->old_parent = dget(old_dentry->d_parent); + return 0; + +out_dput_d2: + dput(d2); +out_unlock: + unlock_rename(old_dentry->d_parent, rd->new_parent); + return err; +} + +/** + * start_renaming_dentry - lookup and lock name for rename with permission checking + * @rd: rename data containing parents and flags, and + * for receiving found dentries + * @lookup_flags: extra flags to pass to ->lookup (e.g. LOOKUP_REVAL, + * LOOKUP_NO_SYMLINKS etc). + * @old_dentry: dentry of name to move + * @new_last: name of target in @rd.new_parent + * + * Look up target name and ensure locks are in place for + * rename. + * + * On success the found dentry is stored in @rd.new_dentry and + * @rd.old_parent is confirmed to be the parent of @old_dentry. If it + * was originally %NULL, it is set. In either case a reference is taken + * so that end_renaming() can have a stable reference to unlock. + * + * References and the lock can be dropped with end_renaming() + * + * The passed in qstr need not have the hash calculated, and basic + * eXecute permission checking is performed against @rd.mnt_idmap. + * + * Returns: zero or an error. + */ +int start_renaming_dentry(struct renamedata *rd, int lookup_flags, + struct dentry *old_dentry, struct qstr *new_last) +{ + int err; + + err = lookup_one_common(rd->mnt_idmap, new_last, rd->new_parent); + if (err) + return err; + return __start_renaming_dentry(rd, lookup_flags, old_dentry, new_last); +} +EXPORT_SYMBOL(start_renaming_dentry); + +/** + * start_renaming_two_dentries - Lock to dentries in given parents for rename + * @rd: rename data containing parent + * @old_dentry: dentry of name to move + * @new_dentry: dentry to move to + * + * Ensure locks are in place for rename and check parentage is still correct. + * + * On success the two dentries are stored in @rd.old_dentry and + * @rd.new_dentry and @rd.old_parent and @rd.new_parent are confirmed to + * be the parents of the dentries. + * + * References and the lock can be dropped with end_renaming() + * + * Returns: zero or an error. + */ +int +start_renaming_two_dentries(struct renamedata *rd, + struct dentry *old_dentry, struct dentry *new_dentry) +{ + struct dentry *trap; + int err; + + /* Already have the dentry - need to be sure to lock the correct parent */ + trap = lock_rename_child(old_dentry, rd->new_parent); + if (IS_ERR(trap)) + return PTR_ERR(trap); + err = -EINVAL; + if (d_unhashed(old_dentry) || + (rd->old_parent && rd->old_parent != old_dentry->d_parent)) + /* old_dentry was removed, or moved and explicit parent requested */ + goto out_unlock; + if (d_unhashed(new_dentry) || + rd->new_parent != new_dentry->d_parent) + /* new_dentry was removed or moved */ + goto out_unlock; + + if (old_dentry == trap) + /* source is an ancestor of target */ + goto out_unlock; + + if (new_dentry == trap) { + /* target is an ancestor of source */ + if (rd->flags & RENAME_EXCHANGE) + err = -EINVAL; + else + err = -ENOTEMPTY; + goto out_unlock; + } + + err = -EEXIST; + if (d_is_positive(new_dentry) && (rd->flags & RENAME_NOREPLACE)) + goto out_unlock; + + rd->old_dentry = dget(old_dentry); + rd->new_dentry = dget(new_dentry); + rd->old_parent = dget(old_dentry->d_parent); + return 0; + +out_unlock: + unlock_rename(old_dentry->d_parent, rd->new_parent); + return err; +} +EXPORT_SYMBOL(start_renaming_two_dentries); + +void end_renaming(struct renamedata *rd) +{ + unlock_rename(rd->old_parent, rd->new_parent); + dput(rd->old_dentry); + dput(rd->new_dentry); + dput(rd->old_parent); +} +EXPORT_SYMBOL(end_renaming); + +/** + * vfs_prepare_mode - prepare the mode to be used for a new inode + * @idmap: idmap of the mount the inode was found from + * @dir: parent directory of the new inode + * @mode: mode of the new inode + * @mask_perms: allowed permission by the vfs + * @type: type of file to be created + * + * This helper consolidates and enforces vfs restrictions on the @mode of a new + * object to be created. + * + * Umask stripping depends on whether the filesystem supports POSIX ACLs (see + * the kernel documentation for mode_strip_umask()). Moving umask stripping + * after setgid stripping allows the same ordering for both non-POSIX ACL and + * POSIX ACL supporting filesystems. + * + * Returns: mode to be passed to the filesystem + */ +static inline umode_t vfs_prepare_mode(struct mnt_idmap *idmap, + const struct inode *dir, umode_t mode, + umode_t mask_perms, umode_t type) +{ + mode = mode_strip_sgid(idmap, dir, mode); + mode = mode_strip_umask(dir, mode); + + /* + * Apply the vfs mandated allowed permission mask and set the type of + * file to be created before we call into the filesystem. + */ + mode &= (mask_perms & ~S_IFMT); + mode |= (type & S_IFMT); + + return mode; +} + +/** + * vfs_create - create new file + * @idmap: idmap of the mount the inode was found from + * @dentry: dentry of the child file + * @mode: mode of the child file + * @di: returns parent inode, if the inode is delegated. + * + * Create a new file. + * + * If the inode has been found through an idmapped mount the idmap of + * the vfsmount must be passed through @idmap. This function will then take + * care to map the inode according to @idmap before checking permissions. + * On non-idmapped mounts or if permission checking is to be performed on the + * raw inode simply pass @nop_mnt_idmap. + */ +int vfs_create(struct mnt_idmap *idmap, struct dentry *dentry, umode_t mode, + struct delegated_inode *di) +{ + struct inode *dir = d_inode(dentry->d_parent); + int error; + + error = may_create_dentry(idmap, dir, dentry); + if (error) + return error; + + if (!dir->i_op->create) + return -EACCES; /* shouldn't it be ENOSYS? */ + + mode = vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG); + error = security_inode_create(dir, dentry, mode); + if (error) + return error; + error = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, di); + if (error) + return error; + error = dir->i_op->create(idmap, dir, dentry, mode); + if (!error) + fsnotify_create(dir, dentry); + return error; +} +EXPORT_SYMBOL(vfs_create); + +int vfs_mkobj(struct dentry *dentry, umode_t mode, + int (*f)(struct dentry *, umode_t, void *), + void *arg) +{ + struct inode *dir = dentry->d_parent->d_inode; + int error = may_create_dentry(&nop_mnt_idmap, dir, dentry); + if (error) + return error; + + mode &= S_IALLUGO; + mode |= S_IFREG; + error = security_inode_create(dir, dentry, mode); + if (error) + return error; + error = f(dentry, mode, arg); + if (!error) + fsnotify_create(dir, dentry); + return error; +} +EXPORT_SYMBOL(vfs_mkobj); + +bool may_open_dev(const struct path *path) +{ + return !(path->mnt->mnt_flags & MNT_NODEV) && + !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV); +} + +static int may_open(struct mnt_idmap *idmap, const struct path *path, + int acc_mode, int flag) +{ + struct dentry *dentry = path->dentry; + struct inode *inode = dentry->d_inode; + int error; + + if (!inode) + return -ENOENT; + + switch (inode->i_mode & S_IFMT) { + case S_IFLNK: + return -ELOOP; + case S_IFDIR: + if (acc_mode & MAY_WRITE) + return -EISDIR; + if (acc_mode & MAY_EXEC) + return -EACCES; + break; + case S_IFBLK: + case S_IFCHR: + if (!may_open_dev(path)) + return -EACCES; + fallthrough; + case S_IFIFO: + case S_IFSOCK: + if (acc_mode & MAY_EXEC) + return -EACCES; + flag &= ~O_TRUNC; + break; + case S_IFREG: + if ((acc_mode & MAY_EXEC) && path_noexec(path)) + return -EACCES; + break; + default: + VFS_BUG_ON_INODE(!IS_ANON_FILE(inode), inode); + } + + error = inode_permission(idmap, inode, MAY_OPEN | acc_mode); + if (error) + return error; + + /* + * An append-only file must be opened in append mode for writing. + */ + if (IS_APPEND(inode)) { + if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) + return -EPERM; + if (flag & O_TRUNC) + return -EPERM; + } + + /* O_NOATIME can only be set by the owner or superuser */ + if (flag & O_NOATIME && !inode_owner_or_capable(idmap, inode)) + return -EPERM; + + return 0; +} + +static int handle_truncate(struct mnt_idmap *idmap, struct file *filp) +{ + const struct path *path = &filp->f_path; + struct inode *inode = path->dentry->d_inode; + int error = get_write_access(inode); + if (error) + return error; + + error = security_file_truncate(filp); + if (!error) { + error = do_truncate(idmap, path->dentry, 0, + ATTR_MTIME|ATTR_CTIME|ATTR_OPEN, + filp); + } + put_write_access(inode); + return error; +} + +static inline int open_to_namei_flags(int flag) +{ + if ((flag & O_ACCMODE) == 3) + flag--; + return flag; +} + +static int may_o_create(struct mnt_idmap *idmap, + const struct path *dir, struct dentry *dentry, + umode_t mode) +{ + int error = security_path_mknod(dir, dentry, mode, 0); + if (error) + return error; + + if (!fsuidgid_has_mapping(dir->dentry->d_sb, idmap)) + return -EOVERFLOW; + + error = inode_permission(idmap, dir->dentry->d_inode, + MAY_WRITE | MAY_EXEC); + if (error) + return error; + + return security_inode_create(dir->dentry->d_inode, dentry, mode); +} + +/** + * atomic_open() - atomically look up, create and open a file + * @path: parent directory path + * @dentry: child to ->atomic_open() + * @file: file to attach child to + * @open_flag: open flags + * @mode: create mode + * @create_error: return value from may_o_create() + * + * Attempt to look up, create and open @dentry, which must be negative, in a + * single call into the filesystem. + * + * If a non-error dentry is returned then: when FMODE_OPENED is set, + * the file will have been attached to @file by the filesystem calling + * finish_open(). If FMODE_OPENED isn't set, the filesystem instead called + * finish_no_open() and the caller will need to perform the open themselves. + * + * FMODE_CREATED is set when the call to ->atomic_open() actually created + * the file. + * + * Returns: the opened or looked-up dentry, or ERR_PTR() on failure. The + * reference to @dentry is consumed in either case. + */ +static struct dentry *atomic_open(const struct path *path, struct dentry *dentry, + struct file *file, + int open_flag, umode_t mode, int create_error) +{ + struct dentry *const DENTRY_NOT_SET = (void *) -1UL; + struct inode *dir_inode = path->dentry->d_inode; + int error; + + file->__f_path.dentry = DENTRY_NOT_SET; + file->__f_path.mnt = path->mnt; + error = dir_inode->i_op->atomic_open(dir_inode, dentry, file, + open_to_namei_flags(open_flag), mode); + d_lookup_done(dentry); + + if (!error) { + if (file->f_mode & FMODE_OPENED) { + /* finish_open() called */ + struct dentry *opened = file->f_path.dentry; + + if (unlikely(opened != dentry)) { + dput(dentry); + dentry = dget(opened); + } + } else if (likely(file->f_path.dentry != DENTRY_NOT_SET)) { + /* finish_no_open() called */ + struct dentry *replaced = file->f_path.dentry; + + if (replaced) { + dput(dentry); + dentry = replaced; + } + if (unlikely(d_is_negative(dentry))) + error = -ENOENT; + } else { + const char *fsname = dentry->d_sb->s_type->name; + + WARN(1, "%s: ->atomic_open() left file->f_path.dentry unset!\n", + fsname); + error = -EIO; + } + } + + if (error) { + if (unlikely(create_error) && error == -ENOENT) { + /* + * Should have done a create, but errored before. + * Some filesystems return -ENOENT directly instead of + * calling finish_no_open() with a negative dentry; + * either way it should only mean the child doesn't exist, + * so a refused create is safe to record here. + */ + audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE); + error = create_error; + } + dput(dentry); + dentry = ERR_PTR(error); + } + return dentry; +} + +/* + * Look up and maybe create and open the last component. + * + * Takes the parent inode lock itself, exclusive if O_CREAT was requested and + * shared otherwise, and drops it again before returning. The caller must not + * hold it. + * + * On success returns the dentry of the last component. If FMODE_OPENED is set + * on file->f_mode the file was also opened and attached to @file; otherwise + * only lookup and creation were performed and the caller has to open it. In + * the latter case the dentry may be negative if O_CREAT hadn't been specified. + * + * Returns ERR_PTR() on failure. + */ +static struct dentry *lookup_open(struct nameidata *nd, struct file *file, + const struct open_flags *op) +{ + struct delegated_inode delegated_inode = { }; + struct mnt_idmap *idmap; + struct dentry *dir = nd->path.dentry; + struct inode *dir_inode = dir->d_inode; + int open_flag; + struct dentry *dentry; + int error, create_error; + umode_t mode; + bool got_write; + +retry: + open_flag = op->open_flag; + got_write = false; + mode = op->mode; + create_error = 0; + + if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) { + got_write = !mnt_want_write(nd->path.mnt); + /* + * do _not_ fail yet - we might not need that or fail with + * a different error; we'll be dropping this one anyway. + */ + } + if (open_flag & O_CREAT) + inode_lock(dir_inode); + else + inode_lock_shared(dir_inode); + + if (unlikely(IS_DEADDIR(dir_inode))) { + dentry = ERR_PTR(-ENOENT); + goto out; + } + + file->f_mode &= ~FMODE_CREATED; + dentry = d_lookup(dir, &nd->last); + for (;;) { + if (!dentry) { + dentry = d_alloc_parallel(dir, &nd->last); + if (IS_ERR(dentry)) + goto out; + } + if (d_in_lookup(dentry)) + break; + + error = d_revalidate(dir_inode, &nd->last, dentry, nd->flags); + if (likely(error > 0)) + break; + if (error) + goto out_dput; + d_invalidate(dentry); + dput(dentry); + dentry = NULL; + } + if (dentry->d_inode) { + /* Cached positive dentry: will open in do_open(). */ + goto out; + } + + if (open_flag & O_CREAT) + audit_inode(nd->name, dir, AUDIT_INODE_PARENT); + + /* + * Checking write permission is tricky, bacuse we don't know if we are + * going to actually need it: O_CREAT opens should work as long as the + * file exists. But checking existence breaks atomicity. The trick is + * to check access and if not granted clear O_CREAT from the flags. + * + * Another problem is returing the "right" error value (e.g. for an + * O_EXCL open we want to return EEXIST not EROFS). + */ + if (unlikely(!got_write)) + open_flag &= ~O_TRUNC; + idmap = mnt_idmap(nd->path.mnt); + if (open_flag & O_CREAT) { + if (open_flag & O_EXCL) + open_flag &= ~O_TRUNC; + mode = vfs_prepare_mode(idmap, dir_inode, mode, mode, mode); + if (likely(got_write)) + create_error = may_o_create(idmap, &nd->path, + dentry, mode); + else + create_error = -EROFS; + } + if (create_error) + open_flag &= ~O_CREAT; + if (dir_inode->i_op->atomic_open) { + if (nd->flags & LOOKUP_DIRECTORY) + open_flag |= O_DIRECTORY; + dentry = atomic_open(&nd->path, dentry, file, open_flag, mode, + create_error); + goto out; + } + + if (d_in_lookup(dentry)) { + struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry, + nd->flags); + d_lookup_done(dentry); + if (unlikely(res)) { + if (IS_ERR(res)) { + error = PTR_ERR(res); + goto out_dput; + } + dput(dentry); + dentry = res; + } + } + if (dentry->d_inode || !(op->open_flag & O_CREAT)) { + /* + * No need to create a file. If lookup returned a positive + * dentry, the file will be opened in do_open(). + */ + goto out; + } + + /* Negative dentry with O_CREAT flag set */ + audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE); + + if (unlikely(create_error)) { + /* should have done a create, but we already errored */ + error = create_error; + goto out_dput; + } + + error = try_break_deleg(dir_inode, LEASE_BREAK_DIR_CREATE, &delegated_inode); + if (error) + goto out_dput; + + file->f_mode |= FMODE_CREATED; + if (!dir_inode->i_op->create) { + error = -EACCES; + goto out_dput; + } + + error = dir_inode->i_op->create(idmap, dir_inode, dentry, mode); + if (error) + goto out_dput; +out: + if (!IS_ERR(dentry)) { + if (file->f_mode & FMODE_CREATED) + fsnotify_create(dir_inode, dentry); + if (file->f_mode & FMODE_OPENED) + fsnotify_open(file); + } + if ((open_flag & O_CREAT) || create_error) + inode_unlock(dir_inode); + else + inode_unlock_shared(dir_inode); + + if (got_write) + mnt_drop_write(nd->path.mnt); + + if (is_delegated(&delegated_inode)) { + /* Must have come through out_dput: dentry is an ERR_PTR() */ + error = break_deleg_wait(&delegated_inode); + + if (!error) + goto retry; + dentry = ERR_PTR(error); + } + + return dentry; + +out_dput: + dput(dentry); + dentry = ERR_PTR(error); + goto out; +} + +/** + * vfs_lookup_open - open and possibly create a regular file + * @parent: directory to contain file + * @last: final component of file name + * @open_flag: O_flags + * @mode: initial permissions for file + * + * Open a file after lookup and/or create. This provides similar + * functionality to open_last_lookups() for non-VFS users, particularly + * nfsd. + * It uses ->atomic_open or ->lookup / ->create / ->open as appropriate. + * + * If the fs object found is not a regular file then an error is returned. + * In some cases, related errors are repurposed so that the caller can + * determine the type of file found from the error. + * -EISDIR : a directory was found + * -ELOOP : a symlink was found + * -ENODEV : a block or character device special file was found + * -EFTYPE : any other non-regular file was found, such as FIFO or SOCK. + * or ->atomic_open responded to __O_REGULAR. + * + * Returns: the opened struct file, or an error. + */ +struct file *vfs_lookup_open(struct path *parent, struct qstr *last, + int open_flag, umode_t mode) +{ + struct file *file __free(fput) = NULL; + struct nameidata nd = {}; + struct open_flags op = {}; + struct dentry *dentry; + int error = 0; + + WARN_ONCE(mode & ~S_IALLUGO, "mode must only have permission bits"); + WARN_ONCE(open_flag & ~(O_ACCMODE|O_CREAT|O_EXCL|O_TRUNC|__O_REGULAR), + "open_flag has unsupported flags"); + + mode |= S_IFREG; + open_flag |= __O_REGULAR; + + error = lookup_noperm_common(last, parent->dentry); + if (error) + return ERR_PTR(error); + + file = alloc_empty_file(open_flag, current_cred()); + if (IS_ERR(file)) + return file; + + nd.path = *parent; + nd.last = *last; + nd.flags = LOOKUP_OPEN; + if (open_flag & O_CREAT) { + nd.flags |= LOOKUP_CREATE; + if (open_flag & O_EXCL) + nd.flags |= LOOKUP_EXCL; + } + op.open_flag = open_flag; + op.mode = mode; + dentry = lookup_open(&nd, file, &op); + + if (IS_ERR(dentry)) + return ERR_CAST(dentry); + + if (d_really_is_negative(dentry)) { + error = -ENOENT; + } else if (!(file->f_mode & FMODE_CREATED) && (open_flag & O_EXCL)) { + error = -EEXIST; + } else if ((dentry->d_inode->i_mode & S_IFMT) != S_IFREG) { + switch (dentry->d_inode->i_mode & S_IFMT) { + case S_IFDIR: + error = -EISDIR; + break; + case S_IFLNK: + error = -ELOOP; + break; + case S_IFBLK: + case S_IFCHR: + error = -ENODEV; + break; + case S_IFIFO: + case S_IFSOCK: + default: + error = -EFTYPE; + break; + } + } else if (!(file->f_mode & FMODE_OPENED)) { + nd.path.dentry = dentry; + error = vfs_open(&nd.path, file); + } + dput(dentry); + + if (error) + return ERR_PTR(error); + return no_free_ptr(file); +} +EXPORT_SYMBOL_FOR_MODULES(vfs_lookup_open, "nfsd"); + +static inline bool trailing_slashes(struct nameidata *nd) +{ + return (bool)nd->last.name[nd->last.len]; +} + +static struct dentry *lookup_fast_for_open(struct nameidata *nd, int open_flag) +{ + struct dentry *dentry; + + if (open_flag & O_CREAT) { + if (trailing_slashes(nd)) + return ERR_PTR(-EISDIR); + + /* Don't bother on an O_EXCL create */ + if (open_flag & O_EXCL) + return NULL; + } + + if (trailing_slashes(nd)) + nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; + + dentry = lookup_fast(nd); + if (IS_ERR_OR_NULL(dentry)) + return dentry; + + if (open_flag & O_CREAT) { + /* Discard negative dentries. Need inode_lock to do the create */ + if (!dentry->d_inode) { + if (!(nd->flags & LOOKUP_RCU)) + dput(dentry); + dentry = NULL; + } + } + return dentry; +} + +static const char *open_last_lookups(struct nameidata *nd, + struct file *file, const struct open_flags *op) +{ + int open_flag = op->open_flag; + struct dentry *dentry; + const char *res; + + nd->flags |= op->intent; + + if (nd->last_type != LAST_NORM) { + if (nd->depth) + put_link(nd); + return handle_dots(nd, nd->last_type); + } + + /* We _can_ be in RCU mode here */ + dentry = lookup_fast_for_open(nd, open_flag); + if (IS_ERR(dentry)) + return ERR_CAST(dentry); + + if (likely(dentry)) + goto finish_lookup; + + if (!(open_flag & O_CREAT)) { + if (WARN_ON_ONCE(nd->flags & LOOKUP_RCU)) + return ERR_PTR(-ECHILD); + } else { + if (nd->flags & LOOKUP_RCU) { + if (!try_to_unlazy(nd)) + return ERR_PTR(-ECHILD); + } + } + + dentry = lookup_open(nd, file, op); + if (IS_ERR(dentry)) + return ERR_CAST(dentry); + + if (file->f_mode & (FMODE_OPENED | FMODE_CREATED)) { + dput(nd->path.dentry); + nd->path.dentry = dentry; + return NULL; + } + +finish_lookup: + if (nd->depth) + put_link(nd); + res = step_into(nd, WALK_TRAILING, dentry); + if (unlikely(res)) + nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); + return res; +} + +/* + * Handle the last step of open() + */ +static int do_open(struct nameidata *nd, + struct file *file, const struct open_flags *op) +{ + struct mnt_idmap *idmap; + int open_flag = op->open_flag; + bool do_truncate; + int acc_mode; + int error; + + if (!(file->f_mode & (FMODE_OPENED | FMODE_CREATED))) { + error = complete_walk(nd); + if (error) + return error; + } + if (!(file->f_mode & FMODE_CREATED)) + audit_inode(nd->name, nd->path.dentry, 0); + idmap = mnt_idmap(nd->path.mnt); + if (open_flag & O_CREAT) { + if ((open_flag & O_EXCL) && !(file->f_mode & FMODE_CREATED)) + return -EEXIST; + if (d_is_dir(nd->path.dentry)) + return -EISDIR; + error = may_create_in_sticky(idmap, nd, + d_backing_inode(nd->path.dentry)); + if (unlikely(error)) + return error; + } + + if ((open_flag & __O_REGULAR) && !d_is_reg(nd->path.dentry)) + return -EFTYPE; + + if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry)) + return -ENOTDIR; + + do_truncate = false; + acc_mode = op->acc_mode; + if (file->f_mode & FMODE_CREATED) { + /* Don't check for write permission, don't truncate */ + open_flag &= ~O_TRUNC; + acc_mode = 0; + } else if (d_is_reg(nd->path.dentry) && open_flag & O_TRUNC) { + error = mnt_want_write(nd->path.mnt); + if (error) + return error; + do_truncate = true; + } + error = may_open(idmap, &nd->path, acc_mode, open_flag); + if (!error && !(file->f_mode & FMODE_OPENED)) + error = vfs_open(&nd->path, file); + if (!error) + error = security_file_post_open(file, op->acc_mode); + if (!error && do_truncate) + error = handle_truncate(idmap, file); + if (unlikely(error > 0)) { + WARN_ON(1); + error = -EINVAL; + } + if (do_truncate) + mnt_drop_write(nd->path.mnt); + return error; +} + +/** + * vfs_tmpfile - create tmpfile + * @idmap: idmap of the mount the inode was found from + * @parentpath: pointer to the path of the base directory + * @file: file descriptor of the new tmpfile + * @mode: mode of the new tmpfile + * + * Create a temporary file. + * + * If the inode has been found through an idmapped mount the idmap of + * the vfsmount must be passed through @idmap. This function will then take + * care to map the inode according to @idmap before checking permissions. + * On non-idmapped mounts or if permission checking is to be performed on the + * raw inode simply pass @nop_mnt_idmap. + */ +int vfs_tmpfile(struct mnt_idmap *idmap, + const struct path *parentpath, + struct file *file, umode_t mode) +{ + struct dentry *child; + struct inode *dir = d_inode(parentpath->dentry); + struct inode *inode; + int error; + int open_flag = file->f_flags; + + /* A tmpfile is I_LINKABLE, so guard its owner like may_o_create(). */ + if (!fsuidgid_has_mapping(dir->i_sb, idmap)) + return -EOVERFLOW; + + /* we want directory to be writable */ + error = inode_permission(idmap, dir, MAY_WRITE | MAY_EXEC); + if (error) + return error; + if (!dir->i_op->tmpfile) + return -EOPNOTSUPP; + child = d_alloc(parentpath->dentry, &slash_name); + if (unlikely(!child)) + return -ENOMEM; + file->__f_path.mnt = parentpath->mnt; + file->__f_path.dentry = child; + mode = vfs_prepare_mode(idmap, dir, mode, mode, mode); + error = dir->i_op->tmpfile(idmap, dir, file, mode); + dput(child); + if (file->f_mode & FMODE_OPENED) + fsnotify_open(file); + if (error) + return error; + /* Don't check for other permissions, the inode was just created */ + error = may_open(idmap, &file->f_path, 0, file->f_flags); + if (error) + return error; + inode = file_inode(file); + if (!(open_flag & O_EXCL)) { + spin_lock(&inode->i_lock); + inode_state_set(inode, I_LINKABLE); + spin_unlock(&inode->i_lock); + } + security_inode_post_create_tmpfile(idmap, inode); + return 0; +} + +/** + * kernel_tmpfile_open - open a tmpfile for kernel internal use + * @idmap: idmap of the mount the inode was found from + * @parentpath: path of the base directory + * @mode: mode of the new tmpfile + * @open_flag: flags + * @cred: credentials for open + * + * Create and open a temporary file. The file is not accounted in nr_files, + * hence this is only for kernel internal use, and must not be installed into + * file tables or such. + */ +struct file *kernel_tmpfile_open(struct mnt_idmap *idmap, + const struct path *parentpath, + umode_t mode, int open_flag, + const struct cred *cred) +{ + struct file *file; + int error; + + file = alloc_empty_file_noaccount(open_flag, cred); + if (IS_ERR(file)) + return file; + + error = vfs_tmpfile(idmap, parentpath, file, mode); + if (error) { + fput(file); + file = ERR_PTR(error); + } + return file; +} +EXPORT_SYMBOL(kernel_tmpfile_open); + +static int do_tmpfile(struct nameidata *nd, unsigned flags, + const struct open_flags *op, + struct file *file) +{ + struct path path; + int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path); + + if (unlikely(error)) + return error; + error = mnt_want_write(path.mnt); + if (unlikely(error)) + goto out; + error = vfs_tmpfile(mnt_idmap(path.mnt), &path, file, op->mode); + if (error) + goto out2; + audit_inode(nd->name, file->f_path.dentry, 0); +out2: + mnt_drop_write(path.mnt); +out: + path_put(&path); + return error; +} + +static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file) +{ + struct path path; + int error = path_lookupat(nd, flags, &path); + if (!error) { + audit_inode(nd->name, path.dentry, 0); + error = vfs_open(&path, file); + path_put(&path); + } + return error; +} + +static struct file *path_openat(struct nameidata *nd, + const struct open_flags *op, unsigned flags) +{ + struct file *file; + int error; + + file = alloc_empty_file(op->open_flag, current_cred()); + if (IS_ERR(file)) + return file; + + if (unlikely(file->f_flags & __O_TMPFILE)) { + error = do_tmpfile(nd, flags, op, file); + } else if (unlikely(file->f_flags & O_PATH)) { + error = do_o_path(nd, flags, file); + } else { + const char *s = path_init(nd, flags); + while (!(error = link_path_walk(s, nd)) && + (s = open_last_lookups(nd, file, op)) != NULL) + ; + if (!error) + error = do_open(nd, file, op); + terminate_walk(nd); + } + if (likely(!error)) { + if (likely(file->f_mode & FMODE_OPENED)) + return file; + WARN_ON(1); + error = -EINVAL; + } + fput_close(file); + if (error == -EOPENSTALE) { + if (flags & LOOKUP_RCU) + error = -ECHILD; + else + error = -ESTALE; + } + return ERR_PTR(error); +} + +struct file *do_file_open(int dfd, struct filename *pathname, + const struct open_flags *op) +{ + struct nameidata nd; + int flags = op->lookup_flags; + struct file *filp; + + if (IS_ERR(pathname)) + return ERR_CAST(pathname); + set_nameidata(&nd, dfd, pathname, NULL); + filp = path_openat(&nd, op, flags | LOOKUP_RCU); + if (unlikely(filp == ERR_PTR(-ECHILD))) + filp = path_openat(&nd, op, flags); + if (unlikely(filp == ERR_PTR(-ESTALE))) + filp = path_openat(&nd, op, flags | LOOKUP_REVAL); + restore_nameidata(); + return filp; +} + +struct file *do_file_open_root(const struct path *root, + const char *name, const struct open_flags *op) +{ + struct nameidata nd; + struct file *file; + int flags = op->lookup_flags; + + if (d_is_symlink(root->dentry) && op->intent & LOOKUP_OPEN) + return ERR_PTR(-ELOOP); + + CLASS(filename_kernel, filename)(name); + if (IS_ERR(filename)) + return ERR_CAST(filename); + + set_nameidata(&nd, -1, filename, root); + file = path_openat(&nd, op, flags | LOOKUP_RCU); + if (unlikely(file == ERR_PTR(-ECHILD))) + file = path_openat(&nd, op, flags); + if (unlikely(file == ERR_PTR(-ESTALE))) + file = path_openat(&nd, op, flags | LOOKUP_REVAL); + restore_nameidata(); + return file; +} + +static struct dentry *filename_create(int dfd, struct filename *name, + struct path *path, unsigned int lookup_flags) +{ + struct dentry *dentry = ERR_PTR(-EEXIST); + struct qstr last; + bool want_dir = lookup_flags & LOOKUP_DIRECTORY; + unsigned int reval_flag = lookup_flags & LOOKUP_REVAL; + unsigned int create_flags = LOOKUP_CREATE | LOOKUP_EXCL; + enum last_type type; + int error; + + error = filename_parentat(dfd, name, reval_flag, path, &last, &type); + if (error) + return ERR_PTR(error); + + /* + * Yucky last component or no last component at all? + * (foo/., foo/.., /////) + */ + if (unlikely(type != LAST_NORM)) + goto out; + + /* don't fail immediately if it's r/o, at least try to report other errors */ + error = mnt_want_write(path->mnt); + /* + * Do the final lookup. Suppress 'create' if there is a trailing + * '/', and a directory wasn't requested. + */ + if (last.name[last.len] && !want_dir) + create_flags &= ~LOOKUP_CREATE; + dentry = start_dirop(path->dentry, &last, reval_flag | create_flags); + if (IS_ERR(dentry)) + goto out_drop_write; + + if (unlikely(error)) + goto fail; + + return dentry; +fail: + end_dirop(dentry); + dentry = ERR_PTR(error); +out_drop_write: + if (!error) + mnt_drop_write(path->mnt); +out: + path_put(path); + return dentry; +} + +struct dentry *start_creating_path(int dfd, const char *pathname, + struct path *path, unsigned int lookup_flags) +{ + CLASS(filename_kernel, filename)(pathname); + return filename_create(dfd, filename, path, lookup_flags); +} +EXPORT_SYMBOL(start_creating_path); + +/** + * end_creating_path - finish a code section started by start_creating_path() + * @path: the path instantiated by start_creating_path() + * @dentry: the dentry returned by start_creating_path() + * + * end_creating_path() will unlock and locks taken by start_creating_path() + * and drop an references that were taken. It should only be called + * if start_creating_path() returned a non-error. + * If vfs_mkdir() was called and it returned an error, that error *should* + * be passed to end_creating_path() together with the path. + */ +void end_creating_path(const struct path *path, struct dentry *dentry) +{ + end_creating(dentry); + mnt_drop_write(path->mnt); + path_put(path); +} +EXPORT_SYMBOL(end_creating_path); + +inline struct dentry *start_creating_user_path( + int dfd, const char __user *pathname, + struct path *path, unsigned int lookup_flags) +{ + CLASS(filename, filename)(pathname); + return filename_create(dfd, filename, path, lookup_flags); +} +EXPORT_SYMBOL(start_creating_user_path); + +/** + * dentry_create - Create and open a file + * @path: path to create + * @flags: O\_ flags + * @mode: mode bits for new file + * @cred: credentials to use + * + * Caller must hold the parent directory's lock, and have prepared + * a negative dentry, placed in @path->dentry, for the new file. + * + * Caller sets @path->mnt to the vfsmount of the filesystem where + * the new file is to be created. The parent directory and the + * negative dentry must reside on the same filesystem instance. + * + * On success, returns a ``struct file *``. Otherwise an ERR_PTR + * is returned. + */ +struct file *dentry_create(struct path *path, int flags, umode_t mode, + const struct cred *cred) +{ + struct file *file __free(fput) = NULL; + struct dentry *dentry = path->dentry; + struct dentry *orig_dentry = dentry; + struct dentry *dir = dentry->d_parent; + struct inode *dir_inode = d_inode(dir); + struct mnt_idmap *idmap; + int error, create_error; + + file = alloc_empty_file(flags, cred); + if (IS_ERR(file)) + return file; + + idmap = mnt_idmap(path->mnt); + + if (dir_inode->i_op->atomic_open) { + path->dentry = dir; + mode = vfs_prepare_mode(idmap, dir_inode, mode, S_IALLUGO, S_IFREG); + + create_error = may_o_create(idmap, path, dentry, mode); + if (create_error) + flags &= ~O_CREAT; + + /* atomic_open will dput(dentry) on error */ + dget(orig_dentry); + dentry = atomic_open(path, dentry, file, flags, mode, create_error); + error = PTR_ERR_OR_ZERO(dentry); + + if (IS_ERR(dentry)) + /* keep the original */ + dentry = orig_dentry; + else + /* Drop the extra reference */ + dput(orig_dentry); + + if (!error) { + if (file->f_mode & FMODE_CREATED) + fsnotify_create(dir->d_inode, dentry); + if (file->f_mode & FMODE_OPENED) + fsnotify_open(file); + } + + path->dentry = dentry; + + } else { + error = vfs_create(mnt_idmap(path->mnt), path->dentry, mode, NULL); + if (!error) + error = vfs_open(path, file); + } + if (unlikely(error)) + return ERR_PTR(error); + + return no_free_ptr(file); +} +EXPORT_SYMBOL(dentry_create); + +/** + * vfs_mknod - create device node or file + * @idmap: idmap of the mount the inode was found from + * @dir: inode of the parent directory + * @dentry: dentry of the child device node + * @mode: mode of the child device node + * @dev: device number of device to create + * @delegated_inode: returns parent inode, if the inode is delegated. + * + * Create a device node or file. + * + * If the inode has been found through an idmapped mount the idmap of + * the vfsmount must be passed through @idmap. This function will then take + * care to map the inode according to @idmap before checking permissions. + * On non-idmapped mounts or if permission checking is to be performed on the + * raw inode simply pass @nop_mnt_idmap. + */ +int vfs_mknod(struct mnt_idmap *idmap, struct inode *dir, + struct dentry *dentry, umode_t mode, dev_t dev, + struct delegated_inode *delegated_inode) +{ + bool is_whiteout = S_ISCHR(mode) && dev == WHITEOUT_DEV; + int error = may_create_dentry(idmap, dir, dentry); + + if (error) + return error; + + if ((S_ISCHR(mode) || S_ISBLK(mode)) && !is_whiteout && + !capable(CAP_MKNOD)) + return -EPERM; + + if (!dir->i_op->mknod) + return -EPERM; + + mode = vfs_prepare_mode(idmap, dir, mode, mode, mode); + error = devcgroup_inode_mknod(mode, dev); + if (error) + return error; + + error = security_inode_mknod(dir, dentry, mode, dev); + if (error) + return error; + + error = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, delegated_inode); + if (error) + return error; + + error = dir->i_op->mknod(idmap, dir, dentry, mode, dev); + if (!error) + fsnotify_create(dir, dentry); + return error; +} +EXPORT_SYMBOL(vfs_mknod); + +static int may_mknod(umode_t mode) +{ + switch (mode & S_IFMT) { + case S_IFREG: + case S_IFCHR: + case S_IFBLK: + case S_IFIFO: + case S_IFSOCK: + case 0: /* zero mode translates to S_IFREG */ + return 0; + case S_IFDIR: + return -EPERM; + default: + return -EINVAL; + } +} + +int filename_mknodat(int dfd, struct filename *name, umode_t mode, + unsigned int dev) +{ + struct delegated_inode di = { }; + struct mnt_idmap *idmap; + struct dentry *dentry; + struct path path; + int error; + unsigned int lookup_flags = 0; + + error = may_mknod(mode); + if (error) + return error; +retry: + dentry = filename_create(dfd, name, &path, lookup_flags); + if (IS_ERR(dentry)) + return PTR_ERR(dentry); + + error = security_path_mknod(&path, dentry, + mode_strip_umask(path.dentry->d_inode, mode), dev); + if (error) + goto out2; + + idmap = mnt_idmap(path.mnt); + switch (mode & S_IFMT) { + case 0: case S_IFREG: + error = vfs_create(idmap, dentry, mode, &di); + if (!error) + security_path_post_mknod(idmap, dentry); + break; + case S_IFCHR: case S_IFBLK: + error = vfs_mknod(idmap, path.dentry->d_inode, + dentry, mode, new_decode_dev(dev), &di); + break; + case S_IFIFO: case S_IFSOCK: + error = vfs_mknod(idmap, path.dentry->d_inode, + dentry, mode, 0, &di); + break; + } +out2: + end_creating_path(&path, dentry); + if (is_delegated(&di)) { + error = break_deleg_wait(&di); + if (!error) + goto retry; + } + if (retry_estale(error, lookup_flags)) { + lookup_flags |= LOOKUP_REVAL; + goto retry; + } + return error; +} + +SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode, + unsigned int, dev) +{ + CLASS(filename, name)(filename); + return filename_mknodat(dfd, name, mode, dev); +} + +SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev) +{ + CLASS(filename, name)(filename); + return filename_mknodat(AT_FDCWD, name, mode, dev); +} + +/** + * vfs_mkdir - create directory returning correct dentry if possible + * @idmap: idmap of the mount the inode was found from + * @dir: inode of the parent directory + * @dentry: dentry of the child directory + * @mode: mode of the child directory + * @delegated_inode: returns parent inode, if the inode is delegated. + * + * Create a directory. + * + * If the inode has been found through an idmapped mount the idmap of + * the vfsmount must be passed through @idmap. This function will then take + * care to map the inode according to @idmap before checking permissions. + * On non-idmapped mounts or if permission checking is to be performed on the + * raw inode simply pass @nop_mnt_idmap. + * + * In the event that the filesystem does not use the *@dentry but leaves it + * negative or unhashes it and possibly splices a different one returning it, + * the original dentry is dput() and the alternate is returned. + * + * In case of an error the dentry is dput() and an ERR_PTR() is returned. + */ +struct dentry *vfs_mkdir(struct mnt_idmap *idmap, struct inode *dir, + struct dentry *dentry, umode_t mode, + struct delegated_inode *delegated_inode) +{ + int error; + unsigned max_links = dir->i_sb->s_max_links; + struct dentry *de; + + error = may_create_dentry(idmap, dir, dentry); + if (error) + goto err; + + error = -EPERM; + if (!dir->i_op->mkdir) + goto err; + + mode = vfs_prepare_mode(idmap, dir, mode, S_IRWXUGO | S_ISVTX, S_IFDIR); + error = security_inode_mkdir(dir, dentry, mode); + if (error) + goto err; + + error = -EMLINK; + if (max_links && dir->i_nlink >= max_links) + goto err; + + error = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, delegated_inode); + if (error) + goto err; + + de = dir->i_op->mkdir(idmap, dir, dentry, mode); + error = PTR_ERR(de); + if (IS_ERR(de)) + goto err; + if (de) { + dput(dentry); + dentry = de; + } + fsnotify_mkdir(dir, dentry); + return dentry; + +err: + end_creating(dentry); + return ERR_PTR(error); +} +EXPORT_SYMBOL(vfs_mkdir); + +int filename_mkdirat(int dfd, struct filename *name, umode_t mode) +{ + struct dentry *dentry; + struct path path; + int error; + unsigned int lookup_flags = LOOKUP_DIRECTORY; + struct delegated_inode delegated_inode = { }; + +retry: + dentry = filename_create(dfd, name, &path, lookup_flags); + if (IS_ERR(dentry)) + return PTR_ERR(dentry); + + error = security_path_mkdir(&path, dentry, + mode_strip_umask(path.dentry->d_inode, mode)); + if (!error) { + dentry = vfs_mkdir(mnt_idmap(path.mnt), path.dentry->d_inode, + dentry, mode, &delegated_inode); + if (IS_ERR(dentry)) + error = PTR_ERR(dentry); + } + end_creating_path(&path, dentry); + if (is_delegated(&delegated_inode)) { + error = break_deleg_wait(&delegated_inode); + if (!error) + goto retry; + } + if (retry_estale(error, lookup_flags)) { + lookup_flags |= LOOKUP_REVAL; + goto retry; + } + return error; +} + +SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode) +{ + CLASS(filename, name)(pathname); + return filename_mkdirat(dfd, name, mode); +} + +SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode) +{ + CLASS(filename, name)(pathname); + return filename_mkdirat(AT_FDCWD, name, mode); +} + +/** + * vfs_rmdir - remove directory + * @idmap: idmap of the mount the inode was found from + * @dir: inode of the parent directory + * @dentry: dentry of the child directory + * @delegated_inode: returns parent inode, if it's delegated. + * + * Remove a directory. + * + * If the inode has been found through an idmapped mount the idmap of + * the vfsmount must be passed through @idmap. This function will then take + * care to map the inode according to @idmap before checking permissions. + * On non-idmapped mounts or if permission checking is to be performed on the + * raw inode simply pass @nop_mnt_idmap. + */ +int vfs_rmdir(struct mnt_idmap *idmap, struct inode *dir, + struct dentry *dentry, struct delegated_inode *delegated_inode) +{ + int error = may_delete_dentry(idmap, dir, dentry, true); + + if (error) + return error; + + if (!dir->i_op->rmdir) + return -EPERM; + + dget(dentry); + inode_lock(dentry->d_inode); + + error = -EBUSY; + if (is_local_mountpoint(dentry) || + (dentry->d_inode->i_flags & S_KERNEL_FILE)) + goto out; + + error = security_inode_rmdir(dir, dentry); + if (error) + goto out; + + error = try_break_deleg(dir, LEASE_BREAK_DIR_DELETE, delegated_inode); + if (error) + goto out; + + error = dir->i_op->rmdir(dir, dentry); + if (error) + goto out; + + shrink_dcache_parent(dentry); + dentry->d_inode->i_flags |= S_DEAD; + dont_mount(dentry); + detach_mounts(dentry); + +out: + inode_unlock(dentry->d_inode); + dput(dentry); + if (!error) + d_delete_notify(dir, dentry); + return error; +} +EXPORT_SYMBOL(vfs_rmdir); + +int filename_rmdir(int dfd, struct filename *name) +{ + int error; + struct dentry *dentry; + struct path path; + struct qstr last; + enum last_type type; + unsigned int lookup_flags = 0; + struct delegated_inode delegated_inode = { }; +retry: + error = filename_parentat(dfd, name, lookup_flags, &path, &last, &type); + if (error) + return error; + + switch (type) { + case LAST_NORM: + break; + case LAST_DOTDOT: + error = -ENOTEMPTY; + goto exit2; + case LAST_DOT: + error = -EINVAL; + goto exit2; + case LAST_ROOT: + error = -EBUSY; + goto exit2; + } + + error = mnt_want_write(path.mnt); + if (error) + goto exit2; + + dentry = start_dirop(path.dentry, &last, lookup_flags); + error = PTR_ERR(dentry); + if (IS_ERR(dentry)) + goto exit3; + error = security_path_rmdir(&path, dentry); + if (error) + goto exit4; + error = vfs_rmdir(mnt_idmap(path.mnt), path.dentry->d_inode, + dentry, &delegated_inode); +exit4: + end_dirop(dentry); +exit3: + mnt_drop_write(path.mnt); +exit2: + path_put(&path); + if (is_delegated(&delegated_inode)) { + error = break_deleg_wait(&delegated_inode); + if (!error) + goto retry; + } + if (retry_estale(error, lookup_flags)) { + lookup_flags |= LOOKUP_REVAL; + goto retry; + } + return error; +} + +SYSCALL_DEFINE1(rmdir, const char __user *, pathname) +{ + CLASS(filename, name)(pathname); + return filename_rmdir(AT_FDCWD, name); +} + +/** + * vfs_unlink - unlink a filesystem object + * @idmap: idmap of the mount the inode was found from + * @dir: parent directory + * @dentry: victim + * @delegated_inode: returns victim inode, if the inode is delegated. + * + * The caller must hold dir->i_rwsem exclusively. + * + * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and + * return a reference to the inode in delegated_inode. The caller + * should then break the delegation on that inode and retry. Because + * breaking a delegation may take a long time, the caller should drop + * dir->i_rwsem before doing so. + * + * Alternatively, a caller may pass NULL for delegated_inode. This may + * be appropriate for callers that expect the underlying filesystem not + * to be NFS exported. + * + * If the inode has been found through an idmapped mount the idmap of + * the vfsmount must be passed through @idmap. This function will then take + * care to map the inode according to @idmap before checking permissions. + * On non-idmapped mounts or if permission checking is to be performed on the + * raw inode simply pass @nop_mnt_idmap. + */ +int vfs_unlink(struct mnt_idmap *idmap, struct inode *dir, + struct dentry *dentry, struct delegated_inode *delegated_inode) +{ + struct inode *target = dentry->d_inode; + int error = may_delete_dentry(idmap, dir, dentry, false); + + if (error) + return error; + + if (!dir->i_op->unlink) + return -EPERM; + + inode_lock(target); + if (IS_SWAPFILE(target)) + error = -EPERM; + else if (is_local_mountpoint(dentry)) + error = -EBUSY; + else { + error = security_inode_unlink(dir, dentry); + if (!error) { + error = try_break_deleg(dir, LEASE_BREAK_DIR_DELETE, delegated_inode); + if (error) + goto out; + error = try_break_deleg(target, 0, delegated_inode); + if (error) + goto out; + error = dir->i_op->unlink(dir, dentry); + if (!error) { + dont_mount(dentry); + detach_mounts(dentry); + } + } + } +out: + inode_unlock(target); + + /* We don't d_delete() NFS sillyrenamed files--they still exist. */ + if (!error && dentry->d_flags & DCACHE_NFSFS_RENAMED) { + fsnotify_unlink(dir, dentry); + } else if (!error) { + fsnotify_link_count(target); + d_delete_notify(dir, dentry); + } + + return error; +} +EXPORT_SYMBOL(vfs_unlink); + +/* + * Make sure that the actual truncation of the file will occur outside its + * directory's i_rwsem. Truncate can take a long time if there is a lot of + * writeout happening, and we don't want to prevent access to the directory + * while waiting on the I/O. + */ +int filename_unlinkat(int dfd, struct filename *name) +{ + int error; + struct dentry *dentry; + struct path path; + struct qstr last; + enum last_type type; + struct inode *inode; + struct delegated_inode delegated_inode = { }; + unsigned int lookup_flags = 0; +retry: + error = filename_parentat(dfd, name, lookup_flags, &path, &last, &type); + if (error) + return error; + + error = -EISDIR; + if (type != LAST_NORM) + goto exit_path_put; + + error = mnt_want_write(path.mnt); + if (error) + goto exit_path_put; +retry_deleg: + dentry = start_dirop(path.dentry, &last, lookup_flags); + error = PTR_ERR(dentry); + if (IS_ERR(dentry)) + goto exit_drop_write; + + /* Why not before? Because we want correct error value */ + if (unlikely(last.name[last.len])) { + if (d_is_dir(dentry)) + error = -EISDIR; + else + error = -ENOTDIR; + end_dirop(dentry); + goto exit_drop_write; + } + inode = dentry->d_inode; + ihold(inode); + error = security_path_unlink(&path, dentry); + if (error) + goto exit_end_dirop; + error = vfs_unlink(mnt_idmap(path.mnt), path.dentry->d_inode, + dentry, &delegated_inode); +exit_end_dirop: + end_dirop(dentry); + iput(inode); /* truncate the inode here */ + if (is_delegated(&delegated_inode)) { + error = break_deleg_wait(&delegated_inode); + if (!error) + goto retry_deleg; + } +exit_drop_write: + mnt_drop_write(path.mnt); +exit_path_put: + path_put(&path); + if (retry_estale(error, lookup_flags)) { + lookup_flags |= LOOKUP_REVAL; + goto retry; + } + return error; +} + +SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag) +{ + if ((flag & ~AT_REMOVEDIR) != 0) + return -EINVAL; + + CLASS(filename, name)(pathname); + if (flag & AT_REMOVEDIR) + return filename_rmdir(dfd, name); + return filename_unlinkat(dfd, name); +} + +SYSCALL_DEFINE1(unlink, const char __user *, pathname) +{ + CLASS(filename, name)(pathname); + return filename_unlinkat(AT_FDCWD, name); +} + +/** + * vfs_symlink - create symlink + * @idmap: idmap of the mount the inode was found from + * @dir: inode of the parent directory + * @dentry: dentry of the child symlink file + * @oldname: name of the file to link to + * @delegated_inode: returns victim inode, if the inode is delegated. + * + * Create a symlink. + * + * If the inode has been found through an idmapped mount the idmap of + * the vfsmount must be passed through @idmap. This function will then take + * care to map the inode according to @idmap before checking permissions. + * On non-idmapped mounts or if permission checking is to be performed on the + * raw inode simply pass @nop_mnt_idmap. + */ +int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir, + struct dentry *dentry, const char *oldname, + struct delegated_inode *delegated_inode) +{ + int error; + + error = may_create_dentry(idmap, dir, dentry); + if (error) + return error; + + if (!dir->i_op->symlink) + return -EPERM; + + error = security_inode_symlink(dir, dentry, oldname); + if (error) + return error; + + error = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, delegated_inode); + if (error) + return error; + + error = dir->i_op->symlink(idmap, dir, dentry, oldname); + if (!error) + fsnotify_create(dir, dentry); + return error; +} +EXPORT_SYMBOL(vfs_symlink); + +int filename_symlinkat(struct filename *from, int newdfd, struct filename *to) +{ + int error; + struct dentry *dentry; + struct path path; + unsigned int lookup_flags = 0; + struct delegated_inode delegated_inode = { }; + + if (IS_ERR(from)) + return PTR_ERR(from); + +retry: + dentry = filename_create(newdfd, to, &path, lookup_flags); + if (IS_ERR(dentry)) + return PTR_ERR(dentry); + + error = security_path_symlink(&path, dentry, from->name); + if (!error) + error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode, + dentry, from->name, &delegated_inode); + end_creating_path(&path, dentry); + if (is_delegated(&delegated_inode)) { + error = break_deleg_wait(&delegated_inode); + if (!error) + goto retry; + } + if (retry_estale(error, lookup_flags)) { + lookup_flags |= LOOKUP_REVAL; + goto retry; + } + return error; +} + +SYSCALL_DEFINE3(symlinkat, const char __user *, oldname, + int, newdfd, const char __user *, newname) +{ + CLASS(filename, old)(oldname); + CLASS(filename, new)(newname); + return filename_symlinkat(old, newdfd, new); +} + +SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname) +{ + CLASS(filename, old)(oldname); + CLASS(filename, new)(newname); + return filename_symlinkat(old, AT_FDCWD, new); +} + +/** + * vfs_link - create a new link + * @old_dentry: object to be linked + * @idmap: idmap of the mount + * @dir: new parent + * @new_dentry: where to create the new link + * @delegated_inode: returns inode needing a delegation break + * + * The caller must hold dir->i_rwsem exclusively. + * + * If vfs_link discovers a delegation on the to-be-linked file in need + * of breaking, it will return -EWOULDBLOCK and return a reference to the + * inode in delegated_inode. The caller should then break the delegation + * and retry. Because breaking a delegation may take a long time, the + * caller should drop the i_rwsem before doing so. + * + * Alternatively, a caller may pass NULL for delegated_inode. This may + * be appropriate for callers that expect the underlying filesystem not + * to be NFS exported. + * + * If the inode has been found through an idmapped mount the idmap of + * the vfsmount must be passed through @idmap. This function will then take + * care to map the inode according to @idmap before checking permissions. + * On non-idmapped mounts or if permission checking is to be performed on the + * raw inode simply pass @nop_mnt_idmap. + */ +int vfs_link(struct dentry *old_dentry, struct mnt_idmap *idmap, + struct inode *dir, struct dentry *new_dentry, + struct delegated_inode *delegated_inode) +{ + struct inode *inode = old_dentry->d_inode; + unsigned max_links = dir->i_sb->s_max_links; + int error; + + if (!inode) + return -ENOENT; + + error = may_create_dentry(idmap, dir, new_dentry); + if (error) + return error; + + if (dir->i_sb != inode->i_sb) + return -EXDEV; + + /* + * A link to an append-only or immutable file cannot be created. + */ + if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) + return -EPERM; + /* + * Updating the link count will likely cause i_uid and i_gid to + * be written back improperly if their true value is unknown to + * the vfs. + */ + if (HAS_UNMAPPED_ID(idmap, inode)) + return -EPERM; + if (!dir->i_op->link) + return -EPERM; + if (S_ISDIR(inode->i_mode)) + return -EPERM; + + error = security_inode_link(old_dentry, dir, new_dentry); + if (error) + return error; + + inode_lock(inode); + /* Make sure we don't allow creating hardlink to an unlinked file */ + if (inode->i_nlink == 0 && !(inode_state_read_once(inode) & I_LINKABLE)) + error = -ENOENT; + else if (max_links && inode->i_nlink >= max_links) + error = -EMLINK; + else { + error = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, delegated_inode); + if (!error) + error = try_break_deleg(inode, 0, delegated_inode); + if (!error) + error = dir->i_op->link(old_dentry, dir, new_dentry); + } + + if (!error && (inode_state_read_once(inode) & I_LINKABLE)) { + spin_lock(&inode->i_lock); + inode_state_clear(inode, I_LINKABLE); + spin_unlock(&inode->i_lock); + } + inode_unlock(inode); + if (!error) + fsnotify_link(dir, inode, new_dentry); + return error; +} +EXPORT_SYMBOL(vfs_link); + +/* + * Hardlinks are often used in delicate situations. We avoid + * security-related surprises by not following symlinks on the + * newname. --KAB + * + * We don't follow them on the oldname either to be compatible + * with linux 2.0, and to avoid hard-linking to directories + * and other special files. --ADM +*/ +int filename_linkat(int olddfd, struct filename *old, + int newdfd, struct filename *new, int flags) +{ + struct mnt_idmap *idmap; + struct dentry *new_dentry; + struct path old_path, new_path; + struct delegated_inode delegated_inode = { }; + int how = 0; + int error; + + if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) + return -EINVAL; + /* + * To use null names we require CAP_DAC_READ_SEARCH or + * that the open-time creds of the dfd matches current. + * This ensures that not everyone will be able to create + * a hardlink using the passed file descriptor. + */ + if (flags & AT_EMPTY_PATH) + how |= LOOKUP_LINKAT_EMPTY; + + if (flags & AT_SYMLINK_FOLLOW) + how |= LOOKUP_FOLLOW; +retry: + error = filename_lookup(olddfd, old, how, &old_path, NULL); + if (error) + return error; + + new_dentry = filename_create(newdfd, new, &new_path, + (how & LOOKUP_REVAL)); + error = PTR_ERR(new_dentry); + if (IS_ERR(new_dentry)) + goto out_putpath; + + error = -EXDEV; + if (old_path.mnt != new_path.mnt) + goto out_dput; + idmap = mnt_idmap(new_path.mnt); + error = may_linkat(idmap, &old_path); + if (unlikely(error)) + goto out_dput; + error = security_path_link(old_path.dentry, &new_path, new_dentry); + if (error) + goto out_dput; + error = vfs_link(old_path.dentry, idmap, new_path.dentry->d_inode, + new_dentry, &delegated_inode); +out_dput: + end_creating_path(&new_path, new_dentry); + if (is_delegated(&delegated_inode)) { + error = break_deleg_wait(&delegated_inode); + if (!error) { + path_put(&old_path); + goto retry; + } + } + if (retry_estale(error, how)) { + path_put(&old_path); + how |= LOOKUP_REVAL; + goto retry; + } +out_putpath: + path_put(&old_path); + return error; +} + +SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname, + int, newdfd, const char __user *, newname, int, flags) +{ + CLASS(filename_uflags, old)(oldname, flags); + CLASS(filename, new)(newname); + return filename_linkat(olddfd, old, newdfd, new, flags); +} + +SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname) +{ + CLASS(filename, old)(oldname); + CLASS(filename, new)(newname); + return filename_linkat(AT_FDCWD, old, AT_FDCWD, new, 0); +} + +/** + * vfs_rename - rename a filesystem object + * @rd: pointer to &struct renamedata info + * + * The caller must hold multiple mutexes--see lock_rename()). + * + * If vfs_rename discovers a delegation in need of breaking at either + * the source or destination, it will return -EWOULDBLOCK and return a + * reference to the inode in delegated_inode. The caller should then + * break the delegation and retry. Because breaking a delegation may + * take a long time, the caller should drop all locks before doing + * so. + * + * Alternatively, a caller may pass NULL for delegated_inode. This may + * be appropriate for callers that expect the underlying filesystem not + * to be NFS exported. + * + * The worst of all namespace operations - renaming directory. "Perverted" + * doesn't even start to describe it. Somebody in UCB had a heck of a trip... + * Problems: + * + * a) we can get into loop creation. + * b) race potential - two innocent renames can create a loop together. + * That's where 4.4BSD screws up. Current fix: serialization on + * sb->s_vfs_rename_mutex. We might be more accurate, but that's another + * story. + * c) we may have to lock up to _four_ objects - parents and victim (if it exists), + * and source (if it's a non-directory or a subdirectory that moves to + * different parent). + * And that - after we got ->i_rwsem on parents (until then we don't know + * whether the target exists). Solution: try to be smart with locking + * order for inodes. We rely on the fact that tree topology may change + * only under ->s_vfs_rename_mutex _and_ that parent of the object we + * move will be locked. Thus we can rank directories by the tree + * (ancestors first) and rank all non-directories after them. + * That works since everybody except rename does "lock parent, lookup, + * lock child" and rename is under ->s_vfs_rename_mutex. + * HOWEVER, it relies on the assumption that any object with ->lookup() + * has no more than 1 dentry. If "hybrid" objects will ever appear, + * we'd better make sure that there's no link(2) for them. + * d) conversion from fhandle to dentry may come in the wrong moment - when + * we are removing the target. Solution: we will have to grab ->i_rwsem + * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on + * ->i_rwsem on parents, which works but leads to some truly excessive + * locking]. + */ +int vfs_rename(struct renamedata *rd) +{ + int error; + struct inode *old_dir = d_inode(rd->old_parent); + struct inode *new_dir = d_inode(rd->new_parent); + struct dentry *old_dentry = rd->old_dentry; + struct dentry *new_dentry = rd->new_dentry; + struct delegated_inode *delegated_inode = rd->delegated_inode; + unsigned int flags = rd->flags; + bool is_dir = d_is_dir(old_dentry); + struct inode *source = old_dentry->d_inode; + struct inode *target = new_dentry->d_inode; + bool new_is_dir = false; + unsigned max_links = new_dir->i_sb->s_max_links; + struct name_snapshot old_name; + bool lock_old_subdir, lock_new_subdir; + + if (source == target) + return 0; + + error = may_delete_dentry(rd->mnt_idmap, old_dir, old_dentry, is_dir); + if (error) + return error; + + if (!target) { + error = may_create_dentry(rd->mnt_idmap, new_dir, new_dentry); + } else { + new_is_dir = d_is_dir(new_dentry); + + if (!(flags & RENAME_EXCHANGE)) + error = may_delete_dentry(rd->mnt_idmap, new_dir, + new_dentry, is_dir); + else + error = may_delete_dentry(rd->mnt_idmap, new_dir, + new_dentry, new_is_dir); + } + if (error) + return error; + + if (!old_dir->i_op->rename) + return -EPERM; + + /* + * If we are going to change the parent - check write permissions, + * we'll need to flip '..'. + */ + if (new_dir != old_dir) { + if (is_dir) { + error = inode_permission(rd->mnt_idmap, source, + MAY_WRITE); + if (error) + return error; + } + if ((flags & RENAME_EXCHANGE) && new_is_dir) { + error = inode_permission(rd->mnt_idmap, target, + MAY_WRITE); + if (error) + return error; + } + } + + error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry, + flags); + if (error) + return error; + + take_dentry_name_snapshot(&old_name, old_dentry); + dget(new_dentry); + /* + * Lock children. + * The source subdirectory needs to be locked on cross-directory + * rename or cross-directory exchange since its parent changes. + * The target subdirectory needs to be locked on cross-directory + * exchange due to parent change and on any rename due to becoming + * a victim. + * Non-directories need locking in all cases (for NFS reasons); + * they get locked after any subdirectories (in inode address order). + * + * NOTE: WE ONLY LOCK UNRELATED DIRECTORIES IN CROSS-DIRECTORY CASE. + * NEVER, EVER DO THAT WITHOUT ->s_vfs_rename_mutex. + */ + lock_old_subdir = new_dir != old_dir; + lock_new_subdir = new_dir != old_dir || !(flags & RENAME_EXCHANGE); + if (is_dir) { + if (lock_old_subdir) + inode_lock_nested(source, I_MUTEX_CHILD); + if (target && (!new_is_dir || lock_new_subdir)) + inode_lock(target); + } else if (new_is_dir) { + if (lock_new_subdir) + inode_lock_nested(target, I_MUTEX_CHILD); + inode_lock(source); + } else { + lock_two_nondirectories(source, target); + } + + error = -EPERM; + if (IS_SWAPFILE(source) || (target && IS_SWAPFILE(target))) + goto out; + + error = -EBUSY; + if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry)) + goto out; + + if (max_links && new_dir != old_dir) { + error = -EMLINK; + if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links) + goto out; + if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir && + old_dir->i_nlink >= max_links) + goto out; + } + error = try_break_deleg(old_dir, + old_dir == new_dir ? LEASE_BREAK_DIR_RENAME : + LEASE_BREAK_DIR_DELETE, + delegated_inode); + if (error) + goto out; + if (new_dir != old_dir) { + error = try_break_deleg(new_dir, LEASE_BREAK_DIR_CREATE, delegated_inode); + if (error) + goto out; + } + if (!is_dir) { + error = try_break_deleg(source, 0, delegated_inode); + if (error) + goto out; + } + if (target && !new_is_dir) { + error = try_break_deleg(target, 0, delegated_inode); + if (error) + goto out; + } + error = old_dir->i_op->rename(rd->mnt_idmap, old_dir, old_dentry, + new_dir, new_dentry, flags); + if (error) + goto out; + + if (!(flags & RENAME_EXCHANGE) && target) { + if (is_dir) { + shrink_dcache_parent(new_dentry); + target->i_flags |= S_DEAD; + } + dont_mount(new_dentry); + detach_mounts(new_dentry); + } + if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) { + if (!(flags & RENAME_EXCHANGE)) + d_move(old_dentry, new_dentry); + else + d_exchange(old_dentry, new_dentry); + } +out: + if (!is_dir || lock_old_subdir) + inode_unlock(source); + if (target && (!new_is_dir || lock_new_subdir)) + inode_unlock(target); + dput(new_dentry); + if (!error) { + fsnotify_move(old_dir, new_dir, &old_name.name, is_dir, + !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry); + if (flags & RENAME_EXCHANGE) { + fsnotify_move(new_dir, old_dir, &old_dentry->d_name, + new_is_dir, NULL, new_dentry); + } + } + release_dentry_name_snapshot(&old_name); + + return error; +} +EXPORT_SYMBOL(vfs_rename); + +int filename_renameat2(int olddfd, struct filename *from, + int newdfd, struct filename *to, unsigned int flags) +{ + struct renamedata rd; + struct path old_path, new_path; + struct qstr old_last, new_last; + enum last_type old_type, new_type; + struct delegated_inode delegated_inode = { }; + unsigned int lookup_flags = 0; + bool should_retry = false; + int error; + + if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT)) + return -EINVAL; + + if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) && + (flags & RENAME_EXCHANGE)) + return -EINVAL; + +retry: + error = filename_parentat(olddfd, from, lookup_flags, &old_path, + &old_last, &old_type); + if (error) + return error; + + error = filename_parentat(newdfd, to, lookup_flags, &new_path, &new_last, + &new_type); + if (error) + goto exit1; + + error = -EXDEV; + if (old_path.mnt != new_path.mnt) + goto exit2; + + error = -EBUSY; + if (old_type != LAST_NORM) + goto exit2; + + if (flags & RENAME_NOREPLACE) + error = -EEXIST; + if (new_type != LAST_NORM) + goto exit2; + + error = mnt_want_write(old_path.mnt); + if (error) + goto exit2; + +retry_deleg: + rd.old_parent = old_path.dentry; + rd.mnt_idmap = mnt_idmap(old_path.mnt); + rd.new_parent = new_path.dentry; + rd.delegated_inode = &delegated_inode; + rd.flags = flags; + + error = __start_renaming(&rd, lookup_flags, &old_last, &new_last); + if (error) + goto exit_lock_rename; + + if (flags & RENAME_EXCHANGE) { + if (!d_is_dir(rd.new_dentry)) { + error = -ENOTDIR; + if (new_last.name[new_last.len]) + goto exit_unlock; + } + } + /* unless the source is a directory trailing slashes give -ENOTDIR */ + if (!d_is_dir(rd.old_dentry)) { + error = -ENOTDIR; + if (old_last.name[old_last.len]) + goto exit_unlock; + if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len]) + goto exit_unlock; + } + + error = security_path_rename(&old_path, rd.old_dentry, + &new_path, rd.new_dentry, flags); + if (error) + goto exit_unlock; + + error = vfs_rename(&rd); +exit_unlock: + end_renaming(&rd); +exit_lock_rename: + if (is_delegated(&delegated_inode)) { + error = break_deleg_wait(&delegated_inode); + if (!error) + goto retry_deleg; + } + mnt_drop_write(old_path.mnt); +exit2: + if (retry_estale(error, lookup_flags)) + should_retry = true; + path_put(&new_path); +exit1: + path_put(&old_path); + if (should_retry) { + should_retry = false; + lookup_flags |= LOOKUP_REVAL; + goto retry; + } + return error; +} + +SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname, + int, newdfd, const char __user *, newname, unsigned int, flags) +{ + CLASS(filename, old)(oldname); + CLASS(filename, new)(newname); + return filename_renameat2(olddfd, old, newdfd, new, flags); +} + +SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname, + int, newdfd, const char __user *, newname) +{ + CLASS(filename, old)(oldname); + CLASS(filename, new)(newname); + return filename_renameat2(olddfd, old, newdfd, new, 0); +} + +SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname) +{ + CLASS(filename, old)(oldname); + CLASS(filename, new)(newname); + return filename_renameat2(AT_FDCWD, old, AT_FDCWD, new, 0); +} + +int readlink_copy(char __user *buffer, int buflen, const char *link, int linklen) +{ + int copylen; + + copylen = linklen; + if (unlikely(copylen > (unsigned) buflen)) + copylen = buflen; + if (copy_to_user(buffer, link, copylen)) + copylen = -EFAULT; + return copylen; +} + +/** + * vfs_readlink - copy symlink body into userspace buffer + * @dentry: dentry on which to get symbolic link + * @buffer: user memory pointer + * @buflen: size of buffer + * + * Does not touch atime. That's up to the caller if necessary + * + * Does not call security hook. + */ +int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen) +{ + struct inode *inode = d_inode(dentry); + DEFINE_DELAYED_CALL(done); + const char *link; + int res; + + if (inode->i_opflags & IOP_CACHED_LINK) + return readlink_copy(buffer, buflen, inode->i_link, inode->i_linklen); + + if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) { + if (unlikely(inode->i_op->readlink)) + return inode->i_op->readlink(dentry, buffer, buflen); + + if (!d_is_symlink(dentry)) + return -EINVAL; + + spin_lock(&inode->i_lock); + inode->i_opflags |= IOP_DEFAULT_READLINK; + spin_unlock(&inode->i_lock); + } + + link = READ_ONCE(inode->i_link); + if (!link) { + link = inode->i_op->get_link(dentry, inode, &done); + if (IS_ERR(link)) + return PTR_ERR(link); + } + res = readlink_copy(buffer, buflen, link, strlen(link)); + do_delayed_call(&done); + return res; +} +EXPORT_SYMBOL(vfs_readlink); + +/** + * vfs_get_link - get symlink body + * @dentry: dentry on which to get symbolic link + * @done: caller needs to free returned data with this + * + * Calls security hook and i_op->get_link() on the supplied inode. + * + * It does not touch atime. That's up to the caller if necessary. + * + * Does not work on "special" symlinks like /proc/$$/fd/N + */ +const char *vfs_get_link(struct dentry *dentry, struct delayed_call *done) +{ + const char *res = ERR_PTR(-EINVAL); + struct inode *inode = d_inode(dentry); + + if (d_is_symlink(dentry)) { + res = ERR_PTR(security_inode_readlink(dentry)); + if (!res) + res = inode->i_op->get_link(dentry, inode, done); + } + return res; +} +EXPORT_SYMBOL(vfs_get_link); + +/* get the link contents into pagecache */ +static char *__page_get_link(struct dentry *dentry, struct inode *inode, + struct delayed_call *callback) +{ + struct folio *folio; + struct address_space *mapping = inode->i_mapping; + + if (!dentry) { + folio = filemap_get_folio(mapping, 0); + if (IS_ERR(folio)) + return ERR_PTR(-ECHILD); + if (!folio_test_uptodate(folio)) { + folio_put(folio); + return ERR_PTR(-ECHILD); + } + } else { + folio = read_mapping_folio(mapping, 0, NULL); + if (IS_ERR(folio)) + return ERR_CAST(folio); + } + set_delayed_call(callback, page_put_link, folio); + BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM); + return folio_address(folio); +} + +const char *page_get_link_raw(struct dentry *dentry, struct inode *inode, + struct delayed_call *callback) +{ + return __page_get_link(dentry, inode, callback); +} +EXPORT_SYMBOL_GPL(page_get_link_raw); + +/** + * page_get_link() - An implementation of the get_link inode_operation. + * @dentry: The directory entry which is the symlink. + * @inode: The inode for the symlink. + * @callback: Used to drop the reference to the symlink. + * + * Filesystems which store their symlinks in the page cache should use + * this to implement the get_link() member of their inode_operations. + * + * Return: A pointer to the NUL-terminated symlink. + */ +const char *page_get_link(struct dentry *dentry, struct inode *inode, + struct delayed_call *callback) +{ + char *kaddr = __page_get_link(dentry, inode, callback); + + if (!IS_ERR(kaddr)) + nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1); + return kaddr; +} +EXPORT_SYMBOL(page_get_link); + +/** + * page_put_link() - Drop the reference to the symlink. + * @arg: The folio which contains the symlink. + * + * This is used internally by page_get_link(). It is exported for use + * by filesystems which need to implement a variant of page_get_link() + * themselves. Despite the apparent symmetry, filesystems which use + * page_get_link() do not need to call page_put_link(). + * + * The argument, while it has a void pointer type, must be a pointer to + * the folio which was retrieved from the page cache. The delayed_call + * infrastructure is used to drop the reference count once the caller + * is done with the symlink. + */ +void page_put_link(void *arg) +{ + folio_put(arg); +} +EXPORT_SYMBOL(page_put_link); + +int page_readlink(struct dentry *dentry, char __user *buffer, int buflen) +{ + const char *link; + int res; + + DEFINE_DELAYED_CALL(done); + link = page_get_link(dentry, d_inode(dentry), &done); + res = PTR_ERR(link); + if (!IS_ERR(link)) + res = readlink_copy(buffer, buflen, link, strlen(link)); + do_delayed_call(&done); + return res; +} +EXPORT_SYMBOL(page_readlink); + +int page_symlink(struct inode *inode, const char *symname, int len) +{ + struct address_space *mapping = inode->i_mapping; + const struct address_space_operations *aops = mapping->a_ops; + bool nofs = !mapping_gfp_constraint(mapping, __GFP_FS); + struct folio *folio; + void *fsdata = NULL; + int err; + unsigned int flags; + +retry: + if (nofs) + flags = memalloc_nofs_save(); + err = aops->write_begin(NULL, mapping, 0, len-1, &folio, &fsdata); + if (nofs) + memalloc_nofs_restore(flags); + if (err) + goto fail; + + memcpy(folio_address(folio), symname, len - 1); + + err = aops->write_end(NULL, mapping, 0, len - 1, len - 1, + folio, fsdata); + if (err < 0) + goto fail; + if (err < len-1) + goto retry; + + mark_inode_dirty(inode); + return 0; +fail: + return err; +} +EXPORT_SYMBOL(page_symlink); + +const struct inode_operations page_symlink_inode_operations = { + .get_link = page_get_link, +}; +EXPORT_SYMBOL(page_symlink_inode_operations); |