diff options
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 6566 |
1 files changed, 6566 insertions, 0 deletions
diff --git a/fs/namespace.c b/fs/namespace.c new file mode 100644 index 000000000..1ecd96c91 --- /dev/null +++ b/fs/namespace.c @@ -0,0 +1,6566 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * linux/fs/namespace.c + * + * (C) Copyright Al Viro 2000, 2001 + * + * Based on code from fs/super.c, copyright Linus Torvalds and others. + * Heavily rewritten. + */ + +#include <linux/syscalls.h> +#include <linux/export.h> +#include <linux/capability.h> +#include <linux/mnt_namespace.h> +#include <linux/user_namespace.h> +#include <linux/namei.h> +#include <linux/security.h> +#include <linux/cred.h> +#include <linux/idr.h> +#include <linux/init.h> /* init_rootfs */ +#include <linux/fs_struct.h> /* get_fs_root et.al. */ +#include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */ +#include <linux/file.h> +#include <linux/uaccess.h> +#include <linux/proc_ns.h> +#include <linux/magic.h> +#include <linux/memblock.h> +#include <linux/proc_fs.h> +#include <linux/task_work.h> +#include <linux/sched/task.h> +#include <uapi/linux/mount.h> +#include <linux/fs_context.h> +#include <linux/shmem_fs.h> +#include <linux/mnt_idmapping.h> +#include <linux/pidfs.h> +#include <linux/nstree.h> + +#include "pnode.h" +#include "internal.h" + +/* Maximum number of mounts in a mount namespace */ +static unsigned int sysctl_mount_max __read_mostly = 100000; + +static unsigned int m_hash_mask __ro_after_init; +static unsigned int m_hash_shift __ro_after_init; +static unsigned int mp_hash_mask __ro_after_init; +static unsigned int mp_hash_shift __ro_after_init; + +static __initdata unsigned long mhash_entries; +static int __init set_mhash_entries(char *str) +{ + return kstrtoul(str, 0, &mhash_entries) == 0; +} +__setup("mhash_entries=", set_mhash_entries); + +static __initdata unsigned long mphash_entries; +static int __init set_mphash_entries(char *str) +{ + return kstrtoul(str, 0, &mphash_entries) == 0; +} +__setup("mphash_entries=", set_mphash_entries); + +static char * __initdata initramfs_options; +static int __init initramfs_options_setup(char *str) +{ + initramfs_options = str; + return 1; +} + +__setup("initramfs_options=", initramfs_options_setup); + +static u64 event; +static DEFINE_XARRAY_FLAGS(mnt_id_xa, XA_FLAGS_ALLOC); +static DEFINE_IDA(mnt_group_ida); + +/* Don't allow confusion with old 32bit mount ID */ +#define MNT_UNIQUE_ID_OFFSET (1ULL << 31) +static u64 mnt_id_ctr = MNT_UNIQUE_ID_OFFSET; + +static struct hlist_head *mount_hashtable __ro_after_init; +static struct hlist_head *mountpoint_hashtable __ro_after_init; +static struct kmem_cache *mnt_cache __ro_after_init; +static DECLARE_RWSEM(namespace_sem); +static HLIST_HEAD(unmounted); /* protected by namespace_sem */ +static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */ +static struct mnt_namespace *emptied_ns; /* protected by namespace_sem */ + +static inline void namespace_lock(void); +static void namespace_unlock(void); +DEFINE_LOCK_GUARD_0(namespace_excl, namespace_lock(), namespace_unlock()) +DEFINE_LOCK_GUARD_0(namespace_shared, down_read(&namespace_sem), + up_read(&namespace_sem)) + +DEFINE_FREE(mntput, struct vfsmount *, if (!IS_ERR(_T)) mntput(_T)) + +#ifdef CONFIG_FSNOTIFY +LIST_HEAD(notify_list); /* protected by namespace_sem */ +#endif + +enum mount_kattr_flags_t { + MOUNT_KATTR_RECURSE = (1 << 0), + MOUNT_KATTR_IDMAP_REPLACE = (1 << 1), +}; + +struct mount_kattr { + unsigned int attr_set; + unsigned int attr_clr; + unsigned int propagation; + unsigned int lookup_flags; + enum mount_kattr_flags_t kflags; + struct user_namespace *mnt_userns; + struct mnt_idmap *mnt_idmap; +}; + +/* /sys/fs */ +struct kobject *fs_kobj __ro_after_init; +EXPORT_SYMBOL_GPL(fs_kobj); + +/* + * vfsmount lock may be taken for read to prevent changes to the + * vfsmount hash, ie. during mountpoint lookups or walking back + * up the tree. + * + * It should be taken for write in all cases where the vfsmount + * tree or hash is modified or when a vfsmount structure is modified. + */ +__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock); + +static void mnt_ns_release(struct mnt_namespace *ns) +{ + /* keep alive for {list,stat}mount() */ + if (ns && refcount_dec_and_test(&ns->passive)) { + fsnotify_mntns_delete(ns); + put_user_ns(ns->user_ns); + kfree(ns); + } +} +DEFINE_FREE(mnt_ns_release, struct mnt_namespace *, + if (!IS_ERR(_T)) mnt_ns_release(_T)) + +static void mnt_ns_release_rcu(struct rcu_head *rcu) +{ + mnt_ns_release(container_of(rcu, struct mnt_namespace, ns.ns_rcu)); +} + +static void mnt_ns_tree_remove(struct mnt_namespace *ns) +{ + /* remove from global mount namespace list */ + if (ns_tree_active(ns)) + ns_tree_remove(ns); + + call_rcu(&ns->ns.ns_rcu, mnt_ns_release_rcu); +} + +/* + * Lookup a mount namespace by id and take a passive reference count. Taking a + * passive reference means the mount namespace can be emptied if e.g., the last + * task holding an active reference exits. To access the mounts of the + * namespace the @namespace_sem must first be acquired. If the namespace has + * already shut down before acquiring @namespace_sem, {list,stat}mount() will + * see that the mount rbtree of the namespace is empty. + * + * Note the lookup is lockless protected by a sequence counter. We only + * need to guard against false negatives as false positives aren't + * possible. So if we didn't find a mount namespace and the sequence + * counter has changed we need to retry. If the sequence counter is + * still the same we know the search actually failed. + */ +static struct mnt_namespace *lookup_mnt_ns(u64 mnt_ns_id) +{ + struct mnt_namespace *mnt_ns; + struct ns_common *ns; + + guard(rcu)(); + ns = ns_tree_lookup_rcu(mnt_ns_id, CLONE_NEWNS); + if (!ns) + return NULL; + + /* + * The last reference count is put with RCU delay so we can + * unconditonally acquire a reference here. + */ + mnt_ns = container_of(ns, struct mnt_namespace, ns); + refcount_inc(&mnt_ns->passive); + return mnt_ns; +} + +static inline void lock_mount_hash(void) +{ + write_seqlock(&mount_lock); +} + +static inline void unlock_mount_hash(void) +{ + write_sequnlock(&mount_lock); +} + +static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry) +{ + unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); + tmp += ((unsigned long)dentry / L1_CACHE_BYTES); + tmp = tmp + (tmp >> m_hash_shift); + return &mount_hashtable[tmp & m_hash_mask]; +} + +static inline struct hlist_head *mp_hash(struct dentry *dentry) +{ + unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES); + tmp = tmp + (tmp >> mp_hash_shift); + return &mountpoint_hashtable[tmp & mp_hash_mask]; +} + +static int mnt_alloc_id(struct mount *mnt) +{ + int res; + + xa_lock(&mnt_id_xa); + res = __xa_alloc(&mnt_id_xa, &mnt->mnt_id, mnt, xa_limit_31b, GFP_KERNEL); + if (!res) + mnt->mnt_id_unique = ++mnt_id_ctr; + xa_unlock(&mnt_id_xa); + return res; +} + +static void mnt_free_id(struct mount *mnt) +{ + xa_erase(&mnt_id_xa, mnt->mnt_id); +} + +/* + * Allocate a new peer group ID + */ +static int mnt_alloc_group_id(struct mount *mnt) +{ + int res = ida_alloc_min(&mnt_group_ida, 1, GFP_KERNEL); + + if (res < 0) + return res; + mnt->mnt_group_id = res; + return 0; +} + +/* + * Release a peer group ID + */ +void mnt_release_group_id(struct mount *mnt) +{ + ida_free(&mnt_group_ida, mnt->mnt_group_id); + mnt->mnt_group_id = 0; +} + +/* + * vfsmount lock must be held for read + */ +static inline void mnt_add_count(struct mount *mnt, int n) +{ +#ifdef CONFIG_SMP + this_cpu_add(mnt->mnt_pcp->mnt_count, n); +#else + preempt_disable(); + mnt->mnt_count += n; + preempt_enable(); +#endif +} + +/* + * vfsmount lock must be held for write + */ +int mnt_get_count(struct mount *mnt) +{ +#ifdef CONFIG_SMP + int count = 0; + int cpu; + + for_each_possible_cpu(cpu) { + count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; + } + + return count; +#else + return mnt->mnt_count; +#endif +} + +static struct mount *alloc_vfsmnt(const char *name) +{ + struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); + if (mnt) { + int err; + + err = mnt_alloc_id(mnt); + if (err) + goto out_free_cache; + + if (name) + mnt->mnt_devname = kstrdup_const(name, + GFP_KERNEL_ACCOUNT); + else + mnt->mnt_devname = "none"; + if (!mnt->mnt_devname) + goto out_free_id; + +#ifdef CONFIG_SMP + mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); + if (!mnt->mnt_pcp) + goto out_free_devname; + + this_cpu_add(mnt->mnt_pcp->mnt_count, 1); +#else + mnt->mnt_count = 1; + mnt->mnt_writers = 0; +#endif + + INIT_HLIST_NODE(&mnt->mnt_hash); + INIT_LIST_HEAD(&mnt->mnt_child); + INIT_LIST_HEAD(&mnt->mnt_mounts); + INIT_LIST_HEAD(&mnt->mnt_list); + INIT_LIST_HEAD(&mnt->mnt_expire); + INIT_LIST_HEAD(&mnt->mnt_share); + INIT_HLIST_HEAD(&mnt->mnt_slave_list); + INIT_HLIST_NODE(&mnt->mnt_slave); + INIT_HLIST_NODE(&mnt->mnt_mp_list); + INIT_HLIST_HEAD(&mnt->mnt_stuck_children); + INIT_HLIST_NODE(&mnt->mnt_ns_visible); + RB_CLEAR_NODE(&mnt->mnt_node); + mnt->mnt.mnt_idmap = &nop_mnt_idmap; + } + return mnt; + +#ifdef CONFIG_SMP +out_free_devname: + kfree_const(mnt->mnt_devname); +#endif +out_free_id: + mnt_free_id(mnt); +out_free_cache: + kmem_cache_free(mnt_cache, mnt); + return NULL; +} + +/* + * Most r/o checks on a fs are for operations that take + * discrete amounts of time, like a write() or unlink(). + * We must keep track of when those operations start + * (for permission checks) and when they end, so that + * we can determine when writes are able to occur to + * a filesystem. + */ +/* + * __mnt_is_readonly: check whether a mount is read-only + * @mnt: the mount to check for its write status + * + * This shouldn't be used directly ouside of the VFS. + * It does not guarantee that the filesystem will stay + * r/w, just that it is right *now*. This can not and + * should not be used in place of IS_RDONLY(inode). + * mnt_want/drop_write() will _keep_ the filesystem + * r/w. + */ +bool __mnt_is_readonly(const struct vfsmount *mnt) +{ + return (mnt->mnt_flags & MNT_READONLY) || sb_rdonly(mnt->mnt_sb); +} +EXPORT_SYMBOL_GPL(__mnt_is_readonly); + +static inline void mnt_inc_writers(struct mount *mnt) +{ +#ifdef CONFIG_SMP + this_cpu_inc(mnt->mnt_pcp->mnt_writers); +#else + mnt->mnt_writers++; +#endif +} + +static inline void mnt_dec_writers(struct mount *mnt) +{ +#ifdef CONFIG_SMP + this_cpu_dec(mnt->mnt_pcp->mnt_writers); +#else + mnt->mnt_writers--; +#endif +} + +static unsigned int mnt_get_writers(struct mount *mnt) +{ +#ifdef CONFIG_SMP + unsigned int count = 0; + int cpu; + + for_each_possible_cpu(cpu) { + count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; + } + + return count; +#else + return mnt->mnt_writers; +#endif +} + +static int mnt_is_readonly(const struct vfsmount *mnt) +{ + if (READ_ONCE(mnt->mnt_sb->s_readonly_remount)) + return 1; + /* + * The barrier pairs with the barrier in sb_start_ro_state_change() + * making sure if we don't see s_readonly_remount set yet, we also will + * not see any superblock / mount flag changes done by remount. + * It also pairs with the barrier in sb_end_ro_state_change() + * assuring that if we see s_readonly_remount already cleared, we will + * see the values of superblock / mount flags updated by remount. + */ + smp_rmb(); + return __mnt_is_readonly(mnt); +} + +/* + * Most r/o & frozen checks on a fs are for operations that take discrete + * amounts of time, like a write() or unlink(). We must keep track of when + * those operations start (for permission checks) and when they end, so that we + * can determine when writes are able to occur to a filesystem. + */ +/** + * mnt_get_write_access - get write access to a mount without freeze protection + * @m: the mount on which to take a write + * + * This tells the low-level filesystem that a write is about to be performed to + * it, and makes sure that writes are allowed (mnt it read-write) before + * returning success. This operation does not protect against filesystem being + * frozen. When the write operation is finished, mnt_put_write_access() must be + * called. This is effectively a refcount. + */ +int mnt_get_write_access(struct vfsmount *m) +{ + struct mount *mnt = real_mount(m); + int ret = 0; + + preempt_disable(); + mnt_inc_writers(mnt); + /* + * The store to mnt_inc_writers must be visible before we pass + * WRITE_HOLD loop below, so that the slowpath can see our + * incremented count after it has set WRITE_HOLD. + */ + smp_mb(); + might_lock(&mount_lock.lock); + while (__test_write_hold(READ_ONCE(mnt->mnt_pprev_for_sb))) { + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) { + cpu_relax(); + } else { + /* + * This prevents priority inversion, if the task + * setting WRITE_HOLD got preempted on a remote + * CPU, and it prevents life lock if the task setting + * WRITE_HOLD has a lower priority and is bound to + * the same CPU as the task that is spinning here. + */ + preempt_enable(); + read_seqlock_excl(&mount_lock); + read_sequnlock_excl(&mount_lock); + preempt_disable(); + } + } + /* + * The barrier pairs with the barrier sb_start_ro_state_change() making + * sure that if we see WRITE_HOLD cleared, we will also see + * s_readonly_remount set (or even SB_RDONLY / MNT_READONLY flags) in + * mnt_is_readonly() and bail in case we are racing with remount + * read-only. + */ + smp_rmb(); + if (mnt_is_readonly(m)) { + mnt_dec_writers(mnt); + ret = -EROFS; + } + preempt_enable(); + + return ret; +} +EXPORT_SYMBOL_GPL(mnt_get_write_access); + +/** + * mnt_want_write - get write access to a mount + * @m: the mount on which to take a write + * + * This tells the low-level filesystem that a write is about to be performed to + * it, and makes sure that writes are allowed (mount is read-write, filesystem + * is not frozen) before returning success. When the write operation is + * finished, mnt_drop_write() must be called. This is effectively a refcount. + */ +int mnt_want_write(struct vfsmount *m) +{ + int ret; + + sb_start_write(m->mnt_sb); + ret = mnt_get_write_access(m); + if (ret) + sb_end_write(m->mnt_sb); + return ret; +} +EXPORT_SYMBOL_GPL(mnt_want_write); + +/** + * mnt_get_write_access_file - get write access to a file's mount + * @file: the file who's mount on which to take a write + * + * This is like mnt_get_write_access, but if @file is already open for write it + * skips incrementing mnt_writers (since the open file already has a reference) + * and instead only does the check for emergency r/o remounts. This must be + * paired with mnt_put_write_access_file. + */ +int mnt_get_write_access_file(struct file *file) +{ + if (file->f_mode & FMODE_WRITER) { + /* + * Superblock may have become readonly while there are still + * writable fd's, e.g. due to a fs error with errors=remount-ro + */ + if (__mnt_is_readonly(file->f_path.mnt)) + return -EROFS; + return 0; + } + return mnt_get_write_access(file->f_path.mnt); +} + +/** + * mnt_want_write_file - get write access to a file's mount + * @file: the file who's mount on which to take a write + * + * This is like mnt_want_write, but if the file is already open for writing it + * skips incrementing mnt_writers (since the open file already has a reference) + * and instead only does the freeze protection and the check for emergency r/o + * remounts. This must be paired with mnt_drop_write_file. + */ +int mnt_want_write_file(struct file *file) +{ + int ret; + + sb_start_write(file_inode(file)->i_sb); + ret = mnt_get_write_access_file(file); + if (ret) + sb_end_write(file_inode(file)->i_sb); + return ret; +} +EXPORT_SYMBOL_GPL(mnt_want_write_file); + +/** + * mnt_put_write_access - give up write access to a mount + * @mnt: the mount on which to give up write access + * + * Tells the low-level filesystem that we are done + * performing writes to it. Must be matched with + * mnt_get_write_access() call above. + */ +void mnt_put_write_access(struct vfsmount *mnt) +{ + preempt_disable(); + mnt_dec_writers(real_mount(mnt)); + preempt_enable(); +} +EXPORT_SYMBOL_GPL(mnt_put_write_access); + +/** + * mnt_drop_write - give up write access to a mount + * @mnt: the mount on which to give up write access + * + * Tells the low-level filesystem that we are done performing writes to it and + * also allows filesystem to be frozen again. Must be matched with + * mnt_want_write() call above. + */ +void mnt_drop_write(struct vfsmount *mnt) +{ + mnt_put_write_access(mnt); + sb_end_write(mnt->mnt_sb); +} +EXPORT_SYMBOL_GPL(mnt_drop_write); + +void mnt_put_write_access_file(struct file *file) +{ + if (!(file->f_mode & FMODE_WRITER)) + mnt_put_write_access(file->f_path.mnt); +} + +void mnt_drop_write_file(struct file *file) +{ + mnt_put_write_access_file(file); + sb_end_write(file_inode(file)->i_sb); +} +EXPORT_SYMBOL(mnt_drop_write_file); + +/** + * mnt_hold_writers - prevent write access to the given mount + * @mnt: mnt to prevent write access to + * + * Prevents write access to @mnt if there are no active writers for @mnt. + * This function needs to be called and return successfully before changing + * properties of @mnt that need to remain stable for callers with write access + * to @mnt. + * + * After this functions has been called successfully callers must pair it with + * a call to mnt_unhold_writers() in order to stop preventing write access to + * @mnt. + * + * Context: This function expects to be in mount_locked_reader scope serializing + * setting WRITE_HOLD. + * Return: On success 0 is returned. + * On error, -EBUSY is returned. + */ +static inline int mnt_hold_writers(struct mount *mnt) +{ + set_write_hold(mnt); + /* + * After storing WRITE_HOLD, we'll read the counters. This store + * should be visible before we do. + */ + smp_mb(); + + /* + * With writers on hold, if this value is zero, then there are + * definitely no active writers (although held writers may subsequently + * increment the count, they'll have to wait, and decrement it after + * seeing MNT_READONLY). + * + * It is OK to have counter incremented on one CPU and decremented on + * another: the sum will add up correctly. The danger would be when we + * sum up each counter, if we read a counter before it is incremented, + * but then read another CPU's count which it has been subsequently + * decremented from -- we would see more decrements than we should. + * WRITE_HOLD protects against this scenario, because + * mnt_want_write first increments count, then smp_mb, then spins on + * WRITE_HOLD, so it can't be decremented by another CPU while + * we're counting up here. + */ + if (mnt_get_writers(mnt) > 0) + return -EBUSY; + + return 0; +} + +/** + * mnt_unhold_writers - stop preventing write access to the given mount + * @mnt: mnt to stop preventing write access to + * + * Stop preventing write access to @mnt allowing callers to gain write access + * to @mnt again. + * + * This function can only be called after a call to mnt_hold_writers(). + * + * Context: This function expects to be in the same mount_locked_reader scope + * as the matching mnt_hold_writers(). + */ +static inline void mnt_unhold_writers(struct mount *mnt) +{ + if (!test_write_hold(mnt)) + return; + /* + * MNT_READONLY must become visible before ~WRITE_HOLD, so writers + * that become unheld will see MNT_READONLY. + */ + smp_wmb(); + clear_write_hold(mnt); +} + +static inline void mnt_del_instance(struct mount *m) +{ + struct mount **p = m->mnt_pprev_for_sb; + struct mount *next = m->mnt_next_for_sb; + + if (next) + next->mnt_pprev_for_sb = p; + *p = next; +} + +static inline void mnt_add_instance(struct mount *m, struct super_block *s) +{ + struct mount *first = s->s_mounts; + + if (first) + first->mnt_pprev_for_sb = &m->mnt_next_for_sb; + m->mnt_next_for_sb = first; + m->mnt_pprev_for_sb = &s->s_mounts; + s->s_mounts = m; +} + +static int mnt_make_readonly(struct mount *mnt) +{ + int ret; + + ret = mnt_hold_writers(mnt); + if (!ret) + mnt->mnt.mnt_flags |= MNT_READONLY; + mnt_unhold_writers(mnt); + return ret; +} + +int sb_prepare_remount_readonly(struct super_block *sb) +{ + int err = 0; + + /* Racy optimization. Recheck the counter under WRITE_HOLD */ + if (atomic_long_read(&sb->s_remove_count)) + return -EBUSY; + + guard(mount_locked_reader)(); + + for (struct mount *m = sb->s_mounts; m; m = m->mnt_next_for_sb) { + if (!(m->mnt.mnt_flags & MNT_READONLY)) { + err = mnt_hold_writers(m); + if (err) + break; + } + } + if (!err && atomic_long_read(&sb->s_remove_count)) + err = -EBUSY; + + if (!err) + sb_start_ro_state_change(sb); + for (struct mount *m = sb->s_mounts; m; m = m->mnt_next_for_sb) { + if (test_write_hold(m)) + clear_write_hold(m); + } + + return err; +} + +static void free_vfsmnt(struct mount *mnt) +{ + mnt_idmap_put(mnt_idmap(&mnt->mnt)); + kfree_const(mnt->mnt_devname); +#ifdef CONFIG_SMP + free_percpu(mnt->mnt_pcp); +#endif + kmem_cache_free(mnt_cache, mnt); +} + +static void delayed_free_vfsmnt(struct rcu_head *head) +{ + free_vfsmnt(container_of(head, struct mount, mnt_rcu)); +} + +/* call under rcu_read_lock */ +int __legitimize_mnt(struct vfsmount *bastard, unsigned seq) +{ + struct mount *mnt; + if (read_seqretry(&mount_lock, seq)) + return 1; + if (bastard == NULL) + return 0; + mnt = real_mount(bastard); + mnt_add_count(mnt, 1); + smp_mb(); // see mntput_no_expire() and do_umount() + if (likely(!read_seqretry(&mount_lock, seq))) + return 0; + lock_mount_hash(); + if (unlikely(bastard->mnt_flags & (MNT_SYNC_UMOUNT | MNT_DOOMED))) { + mnt_add_count(mnt, -1); + unlock_mount_hash(); + return 1; + } + unlock_mount_hash(); + /* caller will mntput() */ + return -1; +} + +/* call under rcu_read_lock */ +static bool legitimize_mnt(struct vfsmount *bastard, unsigned seq) +{ + int res = __legitimize_mnt(bastard, seq); + if (likely(!res)) + return true; + if (unlikely(res < 0)) { + rcu_read_unlock(); + mntput(bastard); + rcu_read_lock(); + } + return false; +} + +/** + * __lookup_mnt - mount hash lookup + * @mnt: parent mount + * @dentry: dentry of mountpoint + * + * If @mnt has a child mount @c mounted on @dentry find and return it. + * Caller must either hold the spinlock component of @mount_lock or + * hold rcu_read_lock(), sample the seqcount component before the call + * and recheck it afterwards. + * + * Return: The child of @mnt mounted on @dentry or %NULL. + */ +struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) +{ + struct hlist_head *head = m_hash(mnt, dentry); + struct mount *p; + + hlist_for_each_entry_rcu(p, head, mnt_hash) + if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) + return p; + return NULL; +} + +/** + * lookup_mnt - Return the child mount mounted at given location + * @path: location in the namespace + * + * Acquires and returns a new reference to mount at given location + * or %NULL if nothing is mounted there. + */ +struct vfsmount *lookup_mnt(const struct path *path) +{ + struct mount *child_mnt; + struct vfsmount *m; + unsigned seq; + + rcu_read_lock(); + do { + seq = read_seqbegin(&mount_lock); + child_mnt = __lookup_mnt(path->mnt, path->dentry); + m = child_mnt ? &child_mnt->mnt : NULL; + } while (!legitimize_mnt(m, seq)); + rcu_read_unlock(); + return m; +} + +/* + * __is_local_mountpoint - Test to see if dentry is a mountpoint in the + * current mount namespace. + * + * The common case is dentries are not mountpoints at all and that + * test is handled inline. For the slow case when we are actually + * dealing with a mountpoint of some kind, walk through all of the + * mounts in the current mount namespace and test to see if the dentry + * is a mountpoint. + * + * The mount_hashtable is not usable in the context because we + * need to identify all mounts that may be in the current mount + * namespace not just a mount that happens to have some specified + * parent mount. + */ +bool __is_local_mountpoint(const struct dentry *dentry) +{ + struct mnt_namespace *ns = current->nsproxy->mnt_ns; + struct mount *mnt, *n; + + guard(namespace_shared)(); + + rbtree_postorder_for_each_entry_safe(mnt, n, &ns->mounts, mnt_node) + if (mnt->mnt_mountpoint == dentry) + return true; + + return false; +} + +struct pinned_mountpoint { + struct hlist_node node; + struct mountpoint *mp; + struct mount *parent; +}; + +static bool lookup_mountpoint(struct dentry *dentry, struct pinned_mountpoint *m) +{ + struct hlist_head *chain = mp_hash(dentry); + struct mountpoint *mp; + + hlist_for_each_entry(mp, chain, m_hash) { + if (mp->m_dentry == dentry) { + hlist_add_head(&m->node, &mp->m_list); + m->mp = mp; + return true; + } + } + return false; +} + +static int get_mountpoint(struct dentry *dentry, struct pinned_mountpoint *m) +{ + struct mountpoint *mp __free(kfree) = NULL; + bool found; + int ret; + + if (d_mountpoint(dentry)) { + /* might be worth a WARN_ON() */ + if (d_unlinked(dentry)) + return -ENOENT; +mountpoint: + read_seqlock_excl(&mount_lock); + found = lookup_mountpoint(dentry, m); + read_sequnlock_excl(&mount_lock); + if (found) + return 0; + } + + if (!mp) + mp = kmalloc_obj(struct mountpoint); + if (!mp) + return -ENOMEM; + + /* Exactly one processes may set d_mounted */ + ret = d_set_mounted(dentry); + + /* Someone else set d_mounted? */ + if (ret == -EBUSY) + goto mountpoint; + + /* The dentry is not available as a mountpoint? */ + if (ret) + return ret; + + /* Add the new mountpoint to the hash table */ + read_seqlock_excl(&mount_lock); + mp->m_dentry = dget(dentry); + hlist_add_head(&mp->m_hash, mp_hash(dentry)); + INIT_HLIST_HEAD(&mp->m_list); + hlist_add_head(&m->node, &mp->m_list); + m->mp = no_free_ptr(mp); + read_sequnlock_excl(&mount_lock); + return 0; +} + +/* + * vfsmount lock must be held. Additionally, the caller is responsible + * for serializing calls for given disposal list. + */ +static void maybe_free_mountpoint(struct mountpoint *mp, struct list_head *list) +{ + if (hlist_empty(&mp->m_list)) { + struct dentry *dentry = mp->m_dentry; + spin_lock(&dentry->d_lock); + dentry->d_flags &= ~DCACHE_MOUNTED; + spin_unlock(&dentry->d_lock); + dput_to_list(dentry, list); + hlist_del(&mp->m_hash); + kfree(mp); + } +} + +/* + * locks: mount_lock [read_seqlock_excl], namespace_sem [excl] + */ +static void unpin_mountpoint(struct pinned_mountpoint *m) +{ + if (m->mp) { + hlist_del(&m->node); + maybe_free_mountpoint(m->mp, &ex_mountpoints); + } +} + +static inline int check_mnt(const struct mount *mnt) +{ + return mnt->mnt_ns == current->nsproxy->mnt_ns; +} + +static inline bool check_anonymous_mnt(struct mount *mnt) +{ + u64 seq; + + if (!is_anon_ns(mnt->mnt_ns)) + return false; + + seq = mnt->mnt_ns->seq_origin; + return !seq || (seq == current->nsproxy->mnt_ns->ns.ns_id); +} + +/* + * vfsmount lock must be held for write + */ +static void touch_mnt_namespace(struct mnt_namespace *ns) +{ + if (ns) { + ns->event = ++event; + wake_up_interruptible(&ns->poll); + } +} + +/* + * vfsmount lock must be held for write + */ +static void __touch_mnt_namespace(struct mnt_namespace *ns) +{ + if (ns && ns->event != event) { + ns->event = event; + wake_up_interruptible(&ns->poll); + } +} + +/* + * locks: mount_lock[write_seqlock] + */ +static void __umount_mnt(struct mount *mnt, struct list_head *shrink_list) +{ + struct mountpoint *mp; + struct mount *parent = mnt->mnt_parent; + if (unlikely(parent->overmount == mnt)) + parent->overmount = NULL; + mnt->mnt_parent = mnt; + mnt->mnt_mountpoint = mnt->mnt.mnt_root; + list_del_init(&mnt->mnt_child); + hlist_del_init_rcu(&mnt->mnt_hash); + hlist_del_init(&mnt->mnt_mp_list); + mp = mnt->mnt_mp; + mnt->mnt_mp = NULL; + maybe_free_mountpoint(mp, shrink_list); +} + +/* + * locks: mount_lock[write_seqlock], namespace_sem[excl] (for ex_mountpoints) + */ +static void umount_mnt(struct mount *mnt) +{ + __umount_mnt(mnt, &ex_mountpoints); +} + +/* + * vfsmount lock must be held for write + */ +void mnt_set_mountpoint(struct mount *mnt, + struct mountpoint *mp, + struct mount *child_mnt) +{ + child_mnt->mnt_mountpoint = mp->m_dentry; + child_mnt->mnt_parent = mnt; + child_mnt->mnt_mp = mp; + hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list); +} + +static void make_visible(struct mount *mnt) +{ + struct mount *parent = mnt->mnt_parent; + if (unlikely(mnt->mnt_mountpoint == parent->mnt.mnt_root)) + parent->overmount = mnt; + hlist_add_head_rcu(&mnt->mnt_hash, + m_hash(&parent->mnt, mnt->mnt_mountpoint)); + list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); +} + +/** + * attach_mnt - mount a mount, attach to @mount_hashtable and parent's + * list of child mounts + * @parent: the parent + * @mnt: the new mount + * @mp: the new mountpoint + * + * Mount @mnt at @mp on @parent. Then attach @mnt + * to @parent's child mount list and to @mount_hashtable. + * + * Note, when make_visible() is called @mnt->mnt_parent already points + * to the correct parent. + * + * Context: This function expects namespace_lock() and lock_mount_hash() + * to have been acquired in that order. + */ +static void attach_mnt(struct mount *mnt, struct mount *parent, + struct mountpoint *mp) +{ + mnt_set_mountpoint(parent, mp, mnt); + make_visible(mnt); +} + +void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt) +{ + struct mountpoint *old_mp = mnt->mnt_mp; + + list_del_init(&mnt->mnt_child); + hlist_del_init(&mnt->mnt_mp_list); + hlist_del_init_rcu(&mnt->mnt_hash); + + attach_mnt(mnt, parent, mp); + + maybe_free_mountpoint(old_mp, &ex_mountpoints); +} + +static inline struct mount *node_to_mount(struct rb_node *node) +{ + return node ? rb_entry(node, struct mount, mnt_node) : NULL; +} + +static void mnt_add_to_ns(struct mnt_namespace *ns, struct mount *mnt) +{ + struct rb_node **link = &ns->mounts.rb_node; + struct rb_node *parent = NULL; + bool mnt_first_node = true, mnt_last_node = true; + + WARN_ON(mnt_ns_attached(mnt)); + WRITE_ONCE(mnt->mnt_ns, ns); + while (*link) { + parent = *link; + if (mnt->mnt_id_unique < node_to_mount(parent)->mnt_id_unique) { + link = &parent->rb_left; + mnt_last_node = false; + } else { + link = &parent->rb_right; + mnt_first_node = false; + } + } + + if (mnt_last_node) + ns->mnt_last_node = &mnt->mnt_node; + if (mnt_first_node) + ns->mnt_first_node = &mnt->mnt_node; + rb_link_node(&mnt->mnt_node, parent, link); + rb_insert_color(&mnt->mnt_node, &ns->mounts); + + if ((mnt->mnt.mnt_sb->s_type->fs_flags & FS_USERNS_MOUNT_RESTRICTED) && + mnt->mnt.mnt_root == mnt->mnt.mnt_sb->s_root) + hlist_add_head(&mnt->mnt_ns_visible, &ns->mnt_visible_mounts); + + mnt_notify_add(mnt); +} + +static struct mount *next_mnt(struct mount *p, struct mount *root) +{ + struct list_head *next = p->mnt_mounts.next; + if (next == &p->mnt_mounts) { + while (1) { + if (p == root) + return NULL; + next = p->mnt_child.next; + if (next != &p->mnt_parent->mnt_mounts) + break; + p = p->mnt_parent; + } + } + return list_entry(next, struct mount, mnt_child); +} + +static struct mount *skip_mnt_tree(struct mount *p) +{ + struct list_head *prev = p->mnt_mounts.prev; + while (prev != &p->mnt_mounts) { + p = list_entry(prev, struct mount, mnt_child); + prev = p->mnt_mounts.prev; + } + return p; +} + +/* + * vfsmount lock must be held for write + */ +static void commit_tree(struct mount *mnt) +{ + struct mnt_namespace *n = mnt->mnt_parent->mnt_ns; + + if (!mnt_ns_attached(mnt)) { + for (struct mount *m = mnt; m; m = next_mnt(m, mnt)) + mnt_add_to_ns(n, m); + n->nr_mounts += n->pending_mounts; + n->pending_mounts = 0; + } + + make_visible(mnt); + touch_mnt_namespace(n); +} + +static void setup_mnt(struct mount *m, struct dentry *root) +{ + struct super_block *s = root->d_sb; + + atomic_inc(&s->s_active); + m->mnt.mnt_sb = s; + m->mnt.mnt_root = dget(root); + m->mnt_mountpoint = m->mnt.mnt_root; + m->mnt_parent = m; + + guard(mount_locked_reader)(); + mnt_add_instance(m, s); +} + +/** + * vfs_create_mount - Create a mount for a configured superblock + * @fc: The configuration context with the superblock attached + * + * Create a mount to an already configured superblock. If necessary, the + * caller should invoke vfs_get_tree() before calling this. + * + * Note that this does not attach the mount to anything. + */ +struct vfsmount *vfs_create_mount(struct fs_context *fc) +{ + struct mount *mnt; + + if (!fc->root) + return ERR_PTR(-EINVAL); + + mnt = alloc_vfsmnt(fc->source); + if (!mnt) + return ERR_PTR(-ENOMEM); + + if (fc->sb_flags & SB_KERNMOUNT) + mnt->mnt.mnt_flags = MNT_INTERNAL; + + setup_mnt(mnt, fc->root); + + return &mnt->mnt; +} +EXPORT_SYMBOL(vfs_create_mount); + +struct vfsmount *fc_mount(struct fs_context *fc) +{ + int err = vfs_get_tree(fc); + if (!err) { + up_write(&fc->root->d_sb->s_umount); + return vfs_create_mount(fc); + } + return ERR_PTR(err); +} +EXPORT_SYMBOL(fc_mount); + +struct vfsmount *fc_mount_longterm(struct fs_context *fc) +{ + struct vfsmount *mnt = fc_mount(fc); + if (!IS_ERR(mnt)) + real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; + return mnt; +} +EXPORT_SYMBOL(fc_mount_longterm); + +struct vfsmount *vfs_kern_mount(struct file_system_type *type, + int flags, const char *name, + void *data) +{ + struct fs_context *fc; + struct vfsmount *mnt; + int ret = 0; + + if (!type) + return ERR_PTR(-EINVAL); + + fc = fs_context_for_mount(type, flags); + if (IS_ERR(fc)) + return ERR_CAST(fc); + + if (name) + ret = vfs_parse_fs_string(fc, "source", name); + if (!ret) + ret = parse_monolithic_mount_data(fc, data); + if (!ret) + mnt = fc_mount(fc); + else + mnt = ERR_PTR(ret); + + put_fs_context(fc); + return mnt; +} +EXPORT_SYMBOL_GPL(vfs_kern_mount); + +static struct mount *clone_mnt(struct mount *old, struct dentry *root, + int flag) +{ + struct mount *mnt; + int err; + + mnt = alloc_vfsmnt(old->mnt_devname); + if (!mnt) + return ERR_PTR(-ENOMEM); + + mnt->mnt.mnt_flags = READ_ONCE(old->mnt.mnt_flags) & + ~MNT_INTERNAL_FLAGS; + + if (flag & (CL_SLAVE | CL_PRIVATE)) + mnt->mnt_group_id = 0; /* not a peer of original */ + else + mnt->mnt_group_id = old->mnt_group_id; + + if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { + err = mnt_alloc_group_id(mnt); + if (err) + goto out_free; + } + + if (mnt->mnt_group_id) + set_mnt_shared(mnt); + + mnt->mnt.mnt_idmap = mnt_idmap_get(mnt_idmap(&old->mnt)); + + setup_mnt(mnt, root); + + if (flag & CL_PRIVATE) // we are done with it + return mnt; + + if (peers(mnt, old)) + list_add(&mnt->mnt_share, &old->mnt_share); + + if ((flag & CL_SLAVE) && old->mnt_group_id) { + hlist_add_head(&mnt->mnt_slave, &old->mnt_slave_list); + mnt->mnt_master = old; + } else if (IS_MNT_SLAVE(old)) { + hlist_add_behind(&mnt->mnt_slave, &old->mnt_slave); + mnt->mnt_master = old->mnt_master; + } + return mnt; + + out_free: + mnt_free_id(mnt); + free_vfsmnt(mnt); + return ERR_PTR(err); +} + +static void cleanup_mnt(struct mount *mnt) +{ + struct hlist_node *p; + struct mount *m; + /* + * The warning here probably indicates that somebody messed + * up a mnt_want/drop_write() pair. If this happens, the + * filesystem was probably unable to make r/w->r/o transitions. + * The locking used to deal with mnt_count decrement provides barriers, + * so mnt_get_writers() below is safe. + */ + WARN_ON(mnt_get_writers(mnt)); + if (unlikely(mnt->mnt_pins.first)) + mnt_pin_kill(mnt); + hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) { + hlist_del(&m->mnt_umount); + mntput(&m->mnt); + } + fsnotify_vfsmount_delete(&mnt->mnt); + dput(mnt->mnt.mnt_root); + deactivate_super(mnt->mnt.mnt_sb); + mnt_free_id(mnt); + call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt); +} + +static void __cleanup_mnt(struct rcu_head *head) +{ + cleanup_mnt(container_of(head, struct mount, mnt_rcu)); +} + +static LLIST_HEAD(delayed_mntput_list); +static void delayed_mntput(struct work_struct *unused) +{ + struct llist_node *node = llist_del_all(&delayed_mntput_list); + struct mount *m, *t; + + llist_for_each_entry_safe(m, t, node, mnt_llist) + cleanup_mnt(m); +} +static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput); + +static void noinline mntput_no_expire_slowpath(struct mount *mnt) +{ + LIST_HEAD(list); + int count; + + VFS_BUG_ON(mnt->mnt_ns); + lock_mount_hash(); + /* + * make sure that if __legitimize_mnt() has not seen us grab + * mount_lock, we'll see their refcount increment here. + */ + smp_mb(); + mnt_add_count(mnt, -1); + count = mnt_get_count(mnt); + if (count != 0) { + WARN_ON(count < 0); + rcu_read_unlock(); + unlock_mount_hash(); + return; + } + if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) { + rcu_read_unlock(); + unlock_mount_hash(); + return; + } + mnt->mnt.mnt_flags |= MNT_DOOMED; + rcu_read_unlock(); + + mnt_del_instance(mnt); + if (unlikely(!list_empty(&mnt->mnt_expire))) + list_del(&mnt->mnt_expire); + + if (unlikely(!list_empty(&mnt->mnt_mounts))) { + struct mount *p, *tmp; + list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) { + __umount_mnt(p, &list); + hlist_add_head(&p->mnt_umount, &mnt->mnt_stuck_children); + } + } + unlock_mount_hash(); + shrink_dentry_list(&list); + + if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) { + struct task_struct *task = current; + if (likely(!(task->flags & PF_KTHREAD))) { + init_task_work(&mnt->mnt_rcu, __cleanup_mnt); + if (!task_work_add(task, &mnt->mnt_rcu, TWA_RESUME)) + return; + } + if (llist_add(&mnt->mnt_llist, &delayed_mntput_list)) + schedule_delayed_work(&delayed_mntput_work, 1); + return; + } + cleanup_mnt(mnt); +} + +static void mntput_no_expire(struct mount *mnt) +{ + rcu_read_lock(); + if (likely(READ_ONCE(mnt->mnt_ns))) { + /* + * Since we don't do lock_mount_hash() here, + * ->mnt_ns can change under us. However, if it's + * non-NULL, then there's a reference that won't + * be dropped until after an RCU delay done after + * turning ->mnt_ns NULL. So if we observe it + * non-NULL under rcu_read_lock(), the reference + * we are dropping is not the final one. + */ + mnt_add_count(mnt, -1); + rcu_read_unlock(); + return; + } + mntput_no_expire_slowpath(mnt); +} + +void mntput(struct vfsmount *mnt) +{ + if (mnt) { + struct mount *m = real_mount(mnt); + /* avoid cacheline pingpong */ + if (unlikely(m->mnt_expiry_mark)) + WRITE_ONCE(m->mnt_expiry_mark, 0); + mntput_no_expire(m); + } +} +EXPORT_SYMBOL(mntput); + +struct vfsmount *mntget(struct vfsmount *mnt) +{ + if (mnt) + mnt_add_count(real_mount(mnt), 1); + return mnt; +} +EXPORT_SYMBOL(mntget); + +/* + * Make a mount point inaccessible to new lookups. + * Because there may still be current users, the caller MUST WAIT + * for an RCU grace period before destroying the mount point. + */ +void mnt_make_shortterm(struct vfsmount *mnt) +{ + if (mnt) + WRITE_ONCE(real_mount(mnt)->mnt_ns, NULL); +} + +/** + * path_is_mountpoint() - Check if path is a mount in the current namespace. + * @path: path to check + * + * d_mountpoint() can only be used reliably to establish if a dentry is + * not mounted in any namespace and that common case is handled inline. + * d_mountpoint() isn't aware of the possibility there may be multiple + * mounts using a given dentry in a different namespace. This function + * checks if the passed in path is a mountpoint rather than the dentry + * alone. + */ +bool path_is_mountpoint(const struct path *path) +{ + unsigned seq; + bool res; + + if (!d_mountpoint(path->dentry)) + return false; + + rcu_read_lock(); + do { + seq = read_seqbegin(&mount_lock); + res = __path_is_mountpoint(path); + } while (read_seqretry(&mount_lock, seq)); + rcu_read_unlock(); + + return res; +} +EXPORT_SYMBOL(path_is_mountpoint); + +struct vfsmount *mnt_clone_internal(const struct path *path) +{ + struct mount *p; + p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE); + if (IS_ERR(p)) + return ERR_CAST(p); + p->mnt.mnt_flags |= MNT_INTERNAL; + return &p->mnt; +} + +/* + * Returns the mount which either has the specified mnt_id, or has the next + * smallest id afer the specified one. + */ +static struct mount *mnt_find_id_at(struct mnt_namespace *ns, u64 mnt_id) +{ + struct rb_node *node = ns->mounts.rb_node; + struct mount *ret = NULL; + + while (node) { + struct mount *m = node_to_mount(node); + + if (mnt_id <= m->mnt_id_unique) { + ret = node_to_mount(node); + if (mnt_id == m->mnt_id_unique) + break; + node = node->rb_left; + } else { + node = node->rb_right; + } + } + return ret; +} + +/* + * Returns the mount which either has the specified mnt_id, or has the next + * greater id before the specified one. + */ +static struct mount *mnt_find_id_at_reverse(struct mnt_namespace *ns, u64 mnt_id) +{ + struct rb_node *node = ns->mounts.rb_node; + struct mount *ret = NULL; + + while (node) { + struct mount *m = node_to_mount(node); + + if (mnt_id >= m->mnt_id_unique) { + ret = node_to_mount(node); + if (mnt_id == m->mnt_id_unique) + break; + node = node->rb_right; + } else { + node = node->rb_left; + } + } + return ret; +} + +#ifdef CONFIG_PROC_FS + +/* iterator; we want it to have access to namespace_sem, thus here... */ +static void *m_start(struct seq_file *m, loff_t *pos) +{ + struct proc_mounts *p = m->private; + struct mount *mnt; + + down_read(&namespace_sem); + + mnt = mnt_find_id_at(p->ns, *pos); + if (mnt) + *pos = mnt->mnt_id_unique; + return mnt; +} + +static void *m_next(struct seq_file *m, void *v, loff_t *pos) +{ + struct mount *mnt = v; + struct rb_node *node = rb_next(&mnt->mnt_node); + + if (node) { + struct mount *next = node_to_mount(node); + *pos = next->mnt_id_unique; + return next; + } + + /* + * No more mounts. Set pos past current mount's ID so that if + * iteration restarts, mnt_find_id_at() returns NULL. + */ + *pos = mnt->mnt_id_unique + 1; + return NULL; +} + +static void m_stop(struct seq_file *m, void *v) +{ + up_read(&namespace_sem); +} + +static int m_show(struct seq_file *m, void *v) +{ + struct proc_mounts *p = m->private; + struct mount *r = v; + return p->show(m, &r->mnt); +} + +const struct seq_operations mounts_op = { + .start = m_start, + .next = m_next, + .stop = m_stop, + .show = m_show, +}; + +#endif /* CONFIG_PROC_FS */ + +/** + * may_umount_tree - check if a mount tree is busy + * @m: root of mount tree + * + * This is called to check if a tree of mounts has any + * open files, pwds, chroots or sub mounts that are + * busy. + */ +int may_umount_tree(struct vfsmount *m) +{ + struct mount *mnt = real_mount(m); + bool busy = false; + + /* write lock needed for mnt_get_count */ + lock_mount_hash(); + for (struct mount *p = mnt; p; p = next_mnt(p, mnt)) { + if (mnt_get_count(p) > (p == mnt ? 2 : 1)) { + busy = true; + break; + } + } + unlock_mount_hash(); + + return !busy; +} + +EXPORT_SYMBOL(may_umount_tree); + +/** + * may_umount - check if a mount point is busy + * @mnt: root of mount + * + * This is called to check if a mount point has any + * open files, pwds, chroots or sub mounts. If the + * mount has sub mounts this will return busy + * regardless of whether the sub mounts are busy. + * + * Doesn't take quota and stuff into account. IOW, in some cases it will + * give false negatives. The main reason why it's here is that we need + * a non-destructive way to look for easily umountable filesystems. + */ +int may_umount(struct vfsmount *mnt) +{ + int ret = 1; + down_read(&namespace_sem); + lock_mount_hash(); + if (propagate_mount_busy(real_mount(mnt), 2)) + ret = 0; + unlock_mount_hash(); + up_read(&namespace_sem); + return ret; +} + +EXPORT_SYMBOL(may_umount); + +#ifdef CONFIG_FSNOTIFY +static void mnt_notify(struct mount *p) +{ + if (!p->prev_ns && p->mnt_ns) { + fsnotify_mnt_attach(p->mnt_ns, &p->mnt); + } else if (p->prev_ns && !p->mnt_ns) { + fsnotify_mnt_detach(p->prev_ns, &p->mnt); + } else if (p->prev_ns == p->mnt_ns) { + fsnotify_mnt_move(p->mnt_ns, &p->mnt); + } else { + fsnotify_mnt_detach(p->prev_ns, &p->mnt); + fsnotify_mnt_attach(p->mnt_ns, &p->mnt); + } + p->prev_ns = p->mnt_ns; +} + +static void notify_mnt_list(void) +{ + struct mount *m, *tmp; + /* + * Notify about mounts that were added/reparented/detached/remain + * connected after unmount. + */ + list_for_each_entry_safe(m, tmp, ¬ify_list, to_notify) { + mnt_notify(m); + list_del_init(&m->to_notify); + } +} + +static bool need_notify_mnt_list(void) +{ + return !list_empty(¬ify_list); +} +#else +static void notify_mnt_list(void) +{ +} + +static bool need_notify_mnt_list(void) +{ + return false; +} +#endif + +static void free_mnt_ns(struct mnt_namespace *); +static void namespace_unlock(void) +{ + struct hlist_head head; + struct hlist_node *p; + struct mount *m; + struct mnt_namespace *ns = emptied_ns; + LIST_HEAD(list); + + hlist_move_list(&unmounted, &head); + list_splice_init(&ex_mountpoints, &list); + emptied_ns = NULL; + + if (need_notify_mnt_list()) { + /* + * No point blocking out concurrent readers while notifications + * are sent. This will also allow statmount()/listmount() to run + * concurrently. + */ + downgrade_write(&namespace_sem); + notify_mnt_list(); + up_read(&namespace_sem); + } else { + up_write(&namespace_sem); + } + if (unlikely(ns)) { + /* Make sure we notice when we leak mounts. */ + VFS_WARN_ON_ONCE(!mnt_ns_empty(ns)); + free_mnt_ns(ns); + } + + shrink_dentry_list(&list); + + if (likely(hlist_empty(&head))) + return; + + synchronize_rcu_expedited(); + + hlist_for_each_entry_safe(m, p, &head, mnt_umount) { + hlist_del(&m->mnt_umount); + mntput(&m->mnt); + } +} + +static inline void namespace_lock(void) +{ + down_write(&namespace_sem); +} + +enum umount_tree_flags { + UMOUNT_SYNC = 1, + UMOUNT_PROPAGATE = 2, + UMOUNT_CONNECTED = 4, +}; + +static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how) +{ + /* Leaving mounts connected is only valid for lazy umounts */ + if (how & UMOUNT_SYNC) + return true; + + /* A mount without a parent has nothing to be connected to */ + if (!mnt_has_parent(mnt)) + return true; + + /* Because the reference counting rules change when mounts are + * unmounted and connected, umounted mounts may not be + * connected to mounted mounts. + */ + if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT)) + return true; + + /* Has it been requested that the mount remain connected? */ + if (how & UMOUNT_CONNECTED) + return false; + + /* Is the mount locked such that it needs to remain connected? */ + if (IS_MNT_LOCKED(mnt)) + return false; + + /* By default disconnect the mount */ + return true; +} + +/* + * mount_lock must be held + * namespace_sem must be held for write + */ +static void umount_tree(struct mount *mnt, enum umount_tree_flags how) +{ + LIST_HEAD(tmp_list); + struct mount *p; + + if (how & UMOUNT_PROPAGATE) + propagate_mount_unlock(mnt); + + /* Gather the mounts to umount */ + for (p = mnt; p; p = next_mnt(p, mnt)) { + p->mnt.mnt_flags |= MNT_UMOUNT; + if (mnt_ns_attached(p)) + move_from_ns(p); + list_add_tail(&p->mnt_list, &tmp_list); + } + + /* Hide the mounts from mnt_mounts */ + list_for_each_entry(p, &tmp_list, mnt_list) { + list_del_init(&p->mnt_child); + } + + /* Add propagated mounts to the tmp_list */ + if (how & UMOUNT_PROPAGATE) + propagate_umount(&tmp_list); + + bulk_make_private(&tmp_list); + + while (!list_empty(&tmp_list)) { + struct mnt_namespace *ns; + bool disconnect; + p = list_first_entry(&tmp_list, struct mount, mnt_list); + list_del_init(&p->mnt_expire); + list_del_init(&p->mnt_list); + ns = p->mnt_ns; + if (ns) { + ns->nr_mounts--; + __touch_mnt_namespace(ns); + } + WRITE_ONCE(p->mnt_ns, NULL); + if (how & UMOUNT_SYNC) + p->mnt.mnt_flags |= MNT_SYNC_UMOUNT; + + disconnect = disconnect_mount(p, how); + if (mnt_has_parent(p)) { + if (!disconnect) { + /* Don't forget about p */ + list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts); + } else { + umount_mnt(p); + } + } + if (disconnect) + hlist_add_head(&p->mnt_umount, &unmounted); + + /* + * At this point p->mnt_ns is NULL, notification will be queued + * only if + * + * - p->prev_ns is non-NULL *and* + * - p->prev_ns->n_fsnotify_marks is non-NULL + * + * This will preclude queuing the mount if this is a cleanup + * after a failed copy_tree() or destruction of an anonymous + * namespace, etc. + */ + mnt_notify_add(p); + } +} + +static void shrink_submounts(struct mount *mnt); + +static int do_umount_root(struct super_block *sb) +{ + int ret = 0; + + down_write(&sb->s_umount); + if (!sb_rdonly(sb)) { + struct fs_context *fc; + + fc = fs_context_for_reconfigure(sb->s_root, SB_RDONLY, + SB_RDONLY); + if (IS_ERR(fc)) { + ret = PTR_ERR(fc); + } else { + ret = parse_monolithic_mount_data(fc, NULL); + if (!ret) + ret = reconfigure_super(fc); + put_fs_context(fc); + } + } + up_write(&sb->s_umount); + return ret; +} + +static int do_umount(struct mount *mnt, int flags) +{ + struct super_block *sb = mnt->mnt.mnt_sb; + int retval; + + retval = security_sb_umount(&mnt->mnt, flags); + if (retval) + return retval; + + /* + * Allow userspace to request a mountpoint be expired rather than + * unmounting unconditionally. Unmount only happens if: + * (1) the mark is already set (the mark is cleared by mntput()) + * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] + */ + if (flags & MNT_EXPIRE) { + if (&mnt->mnt == current->fs->root.mnt || + flags & (MNT_FORCE | MNT_DETACH)) + return -EINVAL; + + /* + * probably don't strictly need the lock here if we examined + * all race cases, but it's a slowpath. + */ + lock_mount_hash(); + if (!list_empty(&mnt->mnt_mounts) || mnt_get_count(mnt) != 2) { + unlock_mount_hash(); + return -EBUSY; + } + unlock_mount_hash(); + + if (!xchg(&mnt->mnt_expiry_mark, 1)) + return -EAGAIN; + } + + /* + * If we may have to abort operations to get out of this + * mount, and they will themselves hold resources we must + * allow the fs to do things. In the Unix tradition of + * 'Gee thats tricky lets do it in userspace' the umount_begin + * might fail to complete on the first run through as other tasks + * must return, and the like. Thats for the mount program to worry + * about for the moment. + */ + + if (flags & MNT_FORCE && sb->s_op->umount_begin) { + sb->s_op->umount_begin(sb); + } + + /* + * No sense to grab the lock for this test, but test itself looks + * somewhat bogus. Suggestions for better replacement? + * Ho-hum... In principle, we might treat that as umount + switch + * to rootfs. GC would eventually take care of the old vfsmount. + * Actually it makes sense, especially if rootfs would contain a + * /reboot - static binary that would close all descriptors and + * call reboot(9). Then init(8) could umount root and exec /reboot. + */ + if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { + /* + * Special case for "unmounting" root ... + * we just try to remount it readonly. + */ + if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) + return -EPERM; + return do_umount_root(sb); + } + + namespace_lock(); + lock_mount_hash(); + + /* Repeat the earlier racy checks, now that we are holding the locks */ + retval = -EINVAL; + if (!check_mnt(mnt)) + goto out; + + if (mnt->mnt.mnt_flags & MNT_LOCKED) + goto out; + + if (!mnt_has_parent(mnt)) /* not the absolute root */ + goto out; + + event++; + if (flags & MNT_DETACH) { + umount_tree(mnt, UMOUNT_PROPAGATE); + retval = 0; + } else { + smp_mb(); // paired with __legitimize_mnt() + shrink_submounts(mnt); + retval = -EBUSY; + if (!propagate_mount_busy(mnt, 2)) { + umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); + retval = 0; + } + } +out: + unlock_mount_hash(); + namespace_unlock(); + return retval; +} + +/* + * __detach_mounts - lazily unmount all mounts on the specified dentry + * + * During unlink, rmdir, and d_drop it is possible to loose the path + * to an existing mountpoint, and wind up leaking the mount. + * detach_mounts allows lazily unmounting those mounts instead of + * leaking them. + * + * The caller may hold dentry->d_inode->i_rwsem. + */ +void __detach_mounts(struct dentry *dentry) +{ + struct pinned_mountpoint mp = {}; + struct mount *mnt; + + guard(namespace_excl)(); + guard(mount_writer)(); + + if (!lookup_mountpoint(dentry, &mp)) + return; + + event++; + while (mp.node.next) { + mnt = hlist_entry(mp.node.next, struct mount, mnt_mp_list); + if (mnt->mnt.mnt_flags & MNT_UMOUNT) { + umount_mnt(mnt); + hlist_add_head(&mnt->mnt_umount, &unmounted); + } + else umount_tree(mnt, UMOUNT_CONNECTED); + } + unpin_mountpoint(&mp); +} + +/* + * Is the caller allowed to modify his namespace? + */ +bool may_mount(void) +{ + return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); +} + +static void warn_mandlock(void) +{ + pr_warn_once("=======================================================\n" + "WARNING: The mand mount option has been deprecated and\n" + " and is ignored by this kernel. Remove the mand\n" + " option from the mount to silence this warning.\n" + "=======================================================\n"); +} + +static int can_umount(const struct path *path, int flags) +{ + struct mount *mnt = real_mount(path->mnt); + struct super_block *sb = path->dentry->d_sb; + + if (!may_mount()) + return -EPERM; + if (!path_mounted(path)) + return -EINVAL; + if (!check_mnt(mnt)) + return -EINVAL; + if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */ + return -EINVAL; + if (flags & MNT_FORCE && !ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) + return -EPERM; + return 0; +} + +// caller is responsible for flags being sane +int path_umount(const struct path *path, int flags) +{ + struct mount *mnt = real_mount(path->mnt); + int ret; + + ret = can_umount(path, flags); + if (!ret) + ret = do_umount(mnt, flags); + + /* we mustn't call path_put() as that would clear mnt_expiry_mark */ + dput(path->dentry); + mntput_no_expire(mnt); + return ret; +} + +static int ksys_umount(char __user *name, int flags) +{ + int lookup_flags = LOOKUP_MOUNTPOINT; + struct path path; + int ret; + + // basic validity checks done first + if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) + return -EINVAL; + + if (!(flags & UMOUNT_NOFOLLOW)) + lookup_flags |= LOOKUP_FOLLOW; + ret = user_path_at(AT_FDCWD, name, lookup_flags, &path); + if (ret) + return ret; + return path_umount(&path, flags); +} + +SYSCALL_DEFINE2(umount, char __user *, name, int, flags) +{ + return ksys_umount(name, flags); +} + +#ifdef __ARCH_WANT_SYS_OLDUMOUNT + +/* + * The 2.0 compatible umount. No flags. + */ +SYSCALL_DEFINE1(oldumount, char __user *, name) +{ + return ksys_umount(name, 0); +} + +#endif + +static bool is_mnt_ns_file(struct dentry *dentry) +{ + struct ns_common *ns; + + /* Is this a proxy for a mount namespace? */ + if (dentry->d_op != &ns_dentry_operations) + return false; + + ns = d_inode(dentry)->i_private; + + return ns->ops == &mntns_operations; +} + +struct ns_common *from_mnt_ns(struct mnt_namespace *mnt) +{ + return &mnt->ns; +} + +struct mnt_namespace *get_sequential_mnt_ns(struct mnt_namespace *mntns, bool previous) +{ + struct ns_common *ns; + + guard(rcu)(); + + for (;;) { + ns = ns_tree_adjoined_rcu(mntns, previous); + if (IS_ERR(ns)) + return ERR_CAST(ns); + + mntns = to_mnt_ns(ns); + + /* + * The last passive reference count is put with RCU + * delay so accessing the mount namespace is not just + * safe but all relevant members are still valid. + */ + if (!ns_capable_noaudit(mntns->user_ns, CAP_SYS_ADMIN)) + continue; + + /* + * We need an active reference count as we're persisting + * the mount namespace and it might already be on its + * deathbed. + */ + if (!ns_ref_get(mntns)) + continue; + + return mntns; + } +} + +struct mnt_namespace *mnt_ns_from_dentry(struct dentry *dentry) +{ + if (!is_mnt_ns_file(dentry)) + return NULL; + + return to_mnt_ns(get_proc_ns(dentry->d_inode)); +} + +static bool mnt_ns_loop(struct dentry *dentry) +{ + /* Could bind mounting the mount namespace inode cause a + * mount namespace loop? + */ + struct mnt_namespace *mnt_ns = mnt_ns_from_dentry(dentry); + + if (!mnt_ns) + return false; + + return current->nsproxy->mnt_ns->ns.ns_id >= mnt_ns->ns.ns_id; +} + +struct mount *copy_tree(struct mount *src_root, struct dentry *dentry, + int flag) +{ + struct mount *res, *src_parent, *src_root_child, *src_mnt, + *dst_parent, *dst_mnt; + + if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(src_root)) + return ERR_PTR(-EINVAL); + + if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry)) + return ERR_PTR(-EINVAL); + + res = dst_mnt = clone_mnt(src_root, dentry, flag); + if (IS_ERR(dst_mnt)) + return dst_mnt; + + src_parent = src_root; + + list_for_each_entry(src_root_child, &src_root->mnt_mounts, mnt_child) { + if (!is_subdir(src_root_child->mnt_mountpoint, dentry)) + continue; + + for (src_mnt = src_root_child; src_mnt; + src_mnt = next_mnt(src_mnt, src_root_child)) { + if (!(flag & CL_COPY_UNBINDABLE) && + IS_MNT_UNBINDABLE(src_mnt)) { + if (src_mnt->mnt.mnt_flags & MNT_LOCKED) { + /* Both unbindable and locked. */ + dst_mnt = ERR_PTR(-EPERM); + goto out; + } else { + src_mnt = skip_mnt_tree(src_mnt); + continue; + } + } + if (!(flag & CL_COPY_MNT_NS_FILE) && + is_mnt_ns_file(src_mnt->mnt.mnt_root)) { + src_mnt = skip_mnt_tree(src_mnt); + continue; + } + while (src_parent != src_mnt->mnt_parent) { + src_parent = src_parent->mnt_parent; + dst_mnt = dst_mnt->mnt_parent; + } + + src_parent = src_mnt; + dst_parent = dst_mnt; + dst_mnt = clone_mnt(src_mnt, src_mnt->mnt.mnt_root, flag); + if (IS_ERR(dst_mnt)) + goto out; + lock_mount_hash(); + if (src_mnt->mnt.mnt_flags & MNT_LOCKED) + dst_mnt->mnt.mnt_flags |= MNT_LOCKED; + if (unlikely(flag & CL_EXPIRE)) { + /* stick the duplicate mount on the same expiry + * list as the original if that was on one */ + if (!list_empty(&src_mnt->mnt_expire)) + list_add(&dst_mnt->mnt_expire, + &src_mnt->mnt_expire); + } + attach_mnt(dst_mnt, dst_parent, src_parent->mnt_mp); + unlock_mount_hash(); + } + } + return res; + +out: + if (res) { + lock_mount_hash(); + umount_tree(res, UMOUNT_SYNC); + unlock_mount_hash(); + } + return dst_mnt; +} + +static inline bool extend_array(struct path **res, struct path **to_free, + unsigned n, unsigned *count, unsigned new_count) +{ + struct path *p; + + if (likely(n < *count)) + return true; + p = kmalloc_objs(struct path, new_count); + if (p && *count) + memcpy(p, *res, *count * sizeof(struct path)); + *count = new_count; + kfree(*to_free); + *to_free = *res = p; + return p; +} + +const struct path *collect_paths(const struct path *path, + struct path *prealloc, unsigned count) +{ + struct mount *root = real_mount(path->mnt); + struct mount *child; + struct path *res = prealloc, *to_free = NULL; + unsigned n = 0; + + guard(namespace_shared)(); + + if (!check_mnt(root)) + return ERR_PTR(-EINVAL); + if (!extend_array(&res, &to_free, 0, &count, 32)) + return ERR_PTR(-ENOMEM); + res[n++] = *path; + list_for_each_entry(child, &root->mnt_mounts, mnt_child) { + if (!is_subdir(child->mnt_mountpoint, path->dentry)) + continue; + for (struct mount *m = child; m; m = next_mnt(m, child)) { + if (!extend_array(&res, &to_free, n, &count, 2 * count)) + return ERR_PTR(-ENOMEM); + res[n].mnt = &m->mnt; + res[n].dentry = m->mnt.mnt_root; + n++; + } + } + if (!extend_array(&res, &to_free, n, &count, count + 1)) + return ERR_PTR(-ENOMEM); + memset(res + n, 0, (count - n) * sizeof(struct path)); + for (struct path *p = res; p->mnt; p++) + path_get(p); + return res; +} + +void drop_collected_paths(const struct path *paths, const struct path *prealloc) +{ + for (const struct path *p = paths; p->mnt; p++) + path_put(p); + if (paths != prealloc) + kfree(paths); +} + +static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *, bool); + +void dissolve_on_fput(struct vfsmount *mnt) +{ + struct mount *m = real_mount(mnt); + + /* + * m used to be the root of anon namespace; if it still is one, + * we need to dissolve the mount tree and free that namespace. + * Let's try to avoid taking namespace_sem if we can determine + * that there's nothing to do without it - rcu_read_lock() is + * enough to make anon_ns_root() memory-safe and once m has + * left its namespace, it's no longer our concern, since it will + * never become a root of anon ns again. + */ + + scoped_guard(rcu) { + if (!anon_ns_root(m)) + return; + } + + scoped_guard(namespace_excl) { + if (!anon_ns_root(m)) + return; + + emptied_ns = m->mnt_ns; + lock_mount_hash(); + umount_tree(m, UMOUNT_CONNECTED); + unlock_mount_hash(); + } +} + +/* locks: namespace_shared && pinned(mnt) || mount_locked_reader */ +static bool __has_locked_children(struct mount *mnt, struct dentry *dentry) +{ + struct mount *child; + + list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { + if (!is_subdir(child->mnt_mountpoint, dentry)) + continue; + + if (child->mnt.mnt_flags & MNT_LOCKED) + return true; + } + return false; +} + +bool has_locked_children(struct mount *mnt, struct dentry *dentry) +{ + guard(mount_locked_reader)(); + return __has_locked_children(mnt, dentry); +} + +/* + * Check that there aren't references to earlier/same mount namespaces in the + * specified subtree. Such references can act as pins for mount namespaces + * that aren't checked by the mount-cycle checking code, thereby allowing + * cycles to be made. + * + * locks: mount_locked_reader || namespace_shared && pinned(subtree) + */ +static bool check_for_nsfs_mounts(struct mount *subtree) +{ + for (struct mount *p = subtree; p; p = next_mnt(p, subtree)) + if (mnt_ns_loop(p->mnt.mnt_root)) + return false; + return true; +} + +/** + * clone_private_mount - create a private clone of a path + * @path: path to clone + * + * This creates a new vfsmount, which will be the clone of @path. The new mount + * will not be attached anywhere in the namespace and will be private (i.e. + * changes to the originating mount won't be propagated into this). + * + * This assumes caller has called or done the equivalent of may_mount(). + * + * Release with mntput(). + */ +struct vfsmount *clone_private_mount(const struct path *path) +{ + struct mount *old_mnt = real_mount(path->mnt); + struct mount *new_mnt; + + guard(namespace_shared)(); + + if (IS_MNT_UNBINDABLE(old_mnt)) + return ERR_PTR(-EINVAL); + + /* + * Make sure the source mount is acceptable. + * Anything mounted in our mount namespace is allowed. + * Otherwise, it must be the root of an anonymous mount + * namespace, and we need to make sure no namespace + * loops get created. + */ + if (!check_mnt(old_mnt)) { + if (!anon_ns_root(old_mnt)) + return ERR_PTR(-EINVAL); + + if (!check_for_nsfs_mounts(old_mnt)) + return ERR_PTR(-EINVAL); + } + + if (!ns_capable(old_mnt->mnt_ns->user_ns, CAP_SYS_ADMIN)) + return ERR_PTR(-EPERM); + + if (__has_locked_children(old_mnt, path->dentry)) + return ERR_PTR(-EINVAL); + + new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE); + if (IS_ERR(new_mnt)) + return ERR_PTR(-EINVAL); + + /* Longterm mount to be removed by kern_unmount*() */ + new_mnt->mnt_ns = MNT_NS_INTERNAL; + return &new_mnt->mnt; +} +EXPORT_SYMBOL_GPL(clone_private_mount); + +static void lock_mnt_tree(struct mount *mnt) +{ + struct mount *p; + + for (p = mnt; p; p = next_mnt(p, mnt)) { + int flags = p->mnt.mnt_flags; + /* Don't allow unprivileged users to change mount flags */ + flags |= MNT_LOCK_ATIME; + + if (flags & MNT_READONLY) + flags |= MNT_LOCK_READONLY; + + if (flags & MNT_NODEV) + flags |= MNT_LOCK_NODEV; + + if (flags & MNT_NOSUID) + flags |= MNT_LOCK_NOSUID; + + if (flags & MNT_NOEXEC) + flags |= MNT_LOCK_NOEXEC; + /* Don't allow unprivileged users to reveal what is under a mount */ + if (list_empty(&p->mnt_expire) && p != mnt) + flags |= MNT_LOCKED; + p->mnt.mnt_flags = flags; + } +} + +static void cleanup_group_ids(struct mount *mnt, struct mount *end) +{ + struct mount *p; + + for (p = mnt; p != end; p = next_mnt(p, mnt)) { + if (p->mnt_group_id && !IS_MNT_SHARED(p)) + mnt_release_group_id(p); + } +} + +static int invent_group_ids(struct mount *mnt, bool recurse) +{ + struct mount *p; + + for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { + if (!p->mnt_group_id) { + int err = mnt_alloc_group_id(p); + if (err) { + cleanup_group_ids(mnt, p); + return err; + } + } + } + + return 0; +} + +int count_mounts(struct mnt_namespace *ns, struct mount *mnt) +{ + unsigned int max = READ_ONCE(sysctl_mount_max); + unsigned int mounts = 0; + struct mount *p; + + if (ns->nr_mounts >= max) + return -ENOSPC; + max -= ns->nr_mounts; + if (ns->pending_mounts >= max) + return -ENOSPC; + max -= ns->pending_mounts; + + for (p = mnt; p; p = next_mnt(p, mnt)) + mounts++; + + if (mounts > max) + return -ENOSPC; + + ns->pending_mounts += mounts; + return 0; +} + +enum mnt_tree_flags_t { + MNT_TREE_BENEATH = BIT(0), + MNT_TREE_PROPAGATION = BIT(1), +}; + +/** + * attach_recursive_mnt - attach a source mount tree + * @source_mnt: mount tree to be attached + * @dest: the context for mounting at the place where the tree should go + * + * NOTE: in the table below explains the semantics when a source mount + * of a given type is attached to a destination mount of a given type. + * --------------------------------------------------------------------------- + * | BIND MOUNT OPERATION | + * |************************************************************************** + * | source-->| shared | private | slave | unbindable | + * | dest | | | | | + * | | | | | | | + * | v | | | | | + * |************************************************************************** + * | shared | shared (++) | shared (+) | shared(+++)| invalid | + * | | | | | | + * |non-shared| shared (+) | private | slave (*) | invalid | + * *************************************************************************** + * A bind operation clones the source mount and mounts the clone on the + * destination mount. + * + * (++) the cloned mount is propagated to all the mounts in the propagation + * tree of the destination mount and the cloned mount is added to + * the peer group of the source mount. + * (+) the cloned mount is created under the destination mount and is marked + * as shared. The cloned mount is added to the peer group of the source + * mount. + * (+++) the mount is propagated to all the mounts in the propagation tree + * of the destination mount and the cloned mount is made slave + * of the same master as that of the source mount. The cloned mount + * is marked as 'shared and slave'. + * (*) the cloned mount is made a slave of the same master as that of the + * source mount. + * + * --------------------------------------------------------------------------- + * | MOVE MOUNT OPERATION | + * |************************************************************************** + * | source-->| shared | private | slave | unbindable | + * | dest | | | | | + * | | | | | | | + * | v | | | | | + * |************************************************************************** + * | shared | shared (+) | shared (+) | shared(+++) | invalid | + * | | | | | | + * |non-shared| shared (+*) | private | slave (*) | unbindable | + * *************************************************************************** + * + * (+) the mount is moved to the destination. And is then propagated to + * all the mounts in the propagation tree of the destination mount. + * (+*) the mount is moved to the destination. + * (+++) the mount is moved to the destination and is then propagated to + * all the mounts belonging to the destination mount's propagation tree. + * the mount is marked as 'shared and slave'. + * (*) the mount continues to be a slave at the new location. + * + * if the source mount is a tree, the operations explained above is + * applied to each mount in the tree. + * Must be called without spinlocks held, since this function can sleep + * in allocations. + * + * Context: The function expects namespace_lock() to be held. + * Return: If @source_mnt was successfully attached 0 is returned. + * Otherwise a negative error code is returned. + */ +static int attach_recursive_mnt(struct mount *source_mnt, + const struct pinned_mountpoint *dest) +{ + struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; + struct mount *dest_mnt = dest->parent; + struct mountpoint *dest_mp = dest->mp; + HLIST_HEAD(tree_list); + struct mnt_namespace *ns = dest_mnt->mnt_ns; + struct pinned_mountpoint root = {}; + struct mountpoint *shorter = NULL; + struct mount *child, *p; + struct mount *top; + struct hlist_node *n; + int err = 0; + bool moving = mnt_has_parent(source_mnt); + + /* + * Preallocate a mountpoint in case the new mounts need to be + * mounted beneath mounts on the same mountpoint. + */ + for (top = source_mnt; unlikely(top->overmount); top = top->overmount) { + if (!shorter && is_mnt_ns_file(top->mnt.mnt_root)) + shorter = top->mnt_mp; + } + err = get_mountpoint(top->mnt.mnt_root, &root); + if (err) + return err; + + /* Is there space to add these mounts to the mount namespace? */ + if (!moving) { + err = count_mounts(ns, source_mnt); + if (err) + goto out; + } + + if (IS_MNT_SHARED(dest_mnt)) { + err = invent_group_ids(source_mnt, true); + if (err) + goto out; + err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list); + } + lock_mount_hash(); + if (err) + goto out_cleanup_ids; + + if (IS_MNT_SHARED(dest_mnt)) { + for (p = source_mnt; p; p = next_mnt(p, source_mnt)) + set_mnt_shared(p); + } + + if (moving) { + umount_mnt(source_mnt); + mnt_notify_add(source_mnt); + /* if the mount is moved, it should no longer be expired + * automatically */ + list_del_init(&source_mnt->mnt_expire); + } else { + if (source_mnt->mnt_ns) { + /* move from anon - the caller will destroy */ + emptied_ns = source_mnt->mnt_ns; + for (p = source_mnt; p; p = next_mnt(p, source_mnt)) + move_from_ns(p); + } + } + + mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt); + /* + * Now the original copy is in the same state as the secondaries - + * its root attached to mountpoint, but not hashed and all mounts + * in it are either in our namespace or in no namespace at all. + * Add the original to the list of copies and deal with the + * rest of work for all of them uniformly. + */ + hlist_add_head(&source_mnt->mnt_hash, &tree_list); + + hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) { + struct mount *q; + hlist_del_init(&child->mnt_hash); + /* Notice when we are propagating across user namespaces */ + if (child->mnt_parent->mnt_ns->user_ns != user_ns) + lock_mnt_tree(child); + q = __lookup_mnt(&child->mnt_parent->mnt, + child->mnt_mountpoint); + commit_tree(child); + if (q) { + struct mount *r = topmost_overmount(child); + struct mountpoint *mp = root.mp; + + if (unlikely(shorter) && child != source_mnt) + mp = shorter; + /* + * If @q was locked it was meant to hide + * whatever was under it. Let @child take over + * that job and lock it, then we can unlock @q. + * That'll allow another namespace to shed @q + * and reveal @child. Clearly, that mounter + * consented to this by not severing the mount + * relationship. Otherwise, what's the point. + */ + if (IS_MNT_LOCKED(q)) { + child->mnt.mnt_flags |= MNT_LOCKED; + q->mnt.mnt_flags &= ~MNT_LOCKED; + } + mnt_change_mountpoint(r, mp, q); + } + } + unpin_mountpoint(&root); + unlock_mount_hash(); + + return 0; + + out_cleanup_ids: + while (!hlist_empty(&tree_list)) { + child = hlist_entry(tree_list.first, struct mount, mnt_hash); + child->mnt_parent->mnt_ns->pending_mounts = 0; + umount_tree(child, UMOUNT_SYNC); + } + unlock_mount_hash(); + cleanup_group_ids(source_mnt, NULL); + out: + ns->pending_mounts = 0; + + read_seqlock_excl(&mount_lock); + unpin_mountpoint(&root); + read_sequnlock_excl(&mount_lock); + + return err; +} + +static inline struct mount *where_to_mount(const struct path *path, + struct dentry **dentry, + bool beneath) +{ + struct mount *m; + + if (unlikely(beneath)) { + m = topmost_overmount(real_mount(path->mnt)); + *dentry = m->mnt_mountpoint; + return m->mnt_parent; + } + m = __lookup_mnt(path->mnt, path->dentry); + if (unlikely(m)) { + m = topmost_overmount(m); + *dentry = m->mnt.mnt_root; + return m; + } + *dentry = path->dentry; + return real_mount(path->mnt); +} + +/** + * do_lock_mount - acquire environment for mounting + * @path: target path + * @res: context to set up + * @beneath: whether the intention is to mount beneath @path + * + * To mount something at given location, we need + * namespace_sem locked exclusive + * inode of dentry we are mounting on locked exclusive + * struct mountpoint for that dentry + * struct mount we are mounting on + * + * Results are stored in caller-supplied context (pinned_mountpoint); + * on success we have res->parent and res->mp pointing to parent and + * mountpoint respectively and res->node inserted into the ->m_list + * of the mountpoint, making sure the mountpoint won't disappear. + * On failure we have res->parent set to ERR_PTR(-E...), res->mp + * left NULL, res->node - empty. + * In case of success do_lock_mount returns with locks acquired (in + * proper order - inode lock nests outside of namespace_sem). + * + * Request to mount on overmounted location is treated as "mount on + * top of whatever's overmounting it"; request to mount beneath + * a location - "mount immediately beneath the topmost mount at that + * place". + * + * In all cases the location must not have been unmounted and the + * chosen mountpoint must be allowed to be mounted on. For "beneath" + * case we also require the location to be at the root of a mount + * that has something mounted on top of it (i.e. has an overmount). + */ +static void do_lock_mount(const struct path *path, + struct pinned_mountpoint *res, + bool beneath) +{ + int err; + + if (unlikely(beneath) && !path_mounted(path)) { + res->parent = ERR_PTR(-EINVAL); + return; + } + + do { + struct dentry *dentry, *d; + struct mount *m, *n; + + scoped_guard(mount_locked_reader) { + m = where_to_mount(path, &dentry, beneath); + if (&m->mnt != path->mnt) { + mntget(&m->mnt); + dget(dentry); + } + } + + inode_lock(dentry->d_inode); + namespace_lock(); + + // check if the chain of mounts (if any) has changed. + scoped_guard(mount_locked_reader) + n = where_to_mount(path, &d, beneath); + + if (unlikely(n != m || dentry != d)) + err = -EAGAIN; // something moved, retry + else if (unlikely(cant_mount(dentry) || !is_mounted(path->mnt))) + err = -ENOENT; // not to be mounted on + else if (beneath && &m->mnt == path->mnt && !m->overmount) + err = -EINVAL; + else + err = get_mountpoint(dentry, res); + + if (unlikely(err)) { + res->parent = ERR_PTR(err); + namespace_unlock(); + inode_unlock(dentry->d_inode); + } else { + res->parent = m; + } + /* + * Drop the temporary references. This is subtle - on success + * we are doing that under namespace_sem, which would normally + * be forbidden. However, in that case we are guaranteed that + * refcounts won't reach zero, since we know that path->mnt + * is mounted and thus all mounts reachable from it are pinned + * and stable, along with their mountpoints and roots. + */ + if (&m->mnt != path->mnt) { + dput(dentry); + mntput(&m->mnt); + } + } while (err == -EAGAIN); +} + +static void __unlock_mount(struct pinned_mountpoint *m) +{ + inode_unlock(m->mp->m_dentry->d_inode); + read_seqlock_excl(&mount_lock); + unpin_mountpoint(m); + read_sequnlock_excl(&mount_lock); + namespace_unlock(); +} + +static inline void unlock_mount(struct pinned_mountpoint *m) +{ + if (!IS_ERR(m->parent)) + __unlock_mount(m); +} + +static void lock_mount_exact(const struct path *path, + struct pinned_mountpoint *mp, bool copy_mount, + unsigned int copy_flags); + +#define LOCK_MOUNT_MAYBE_BENEATH(mp, path, beneath) \ + struct pinned_mountpoint mp __cleanup(unlock_mount) = {}; \ + do_lock_mount((path), &mp, (beneath)) +#define LOCK_MOUNT(mp, path) LOCK_MOUNT_MAYBE_BENEATH(mp, (path), false) +#define LOCK_MOUNT_EXACT(mp, path) \ + struct pinned_mountpoint mp __cleanup(unlock_mount) = {}; \ + lock_mount_exact((path), &mp, false, 0) +#define LOCK_MOUNT_EXACT_COPY(mp, path, copy_flags) \ + struct pinned_mountpoint mp __cleanup(unlock_mount) = {}; \ + lock_mount_exact((path), &mp, true, (copy_flags)) + +static int graft_tree(struct mount *mnt, const struct pinned_mountpoint *mp) +{ + if (mnt->mnt.mnt_sb->s_flags & SB_NOUSER) + return -EINVAL; + + if (d_is_dir(mp->mp->m_dentry) != + d_is_dir(mnt->mnt.mnt_root)) + return -ENOTDIR; + + return attach_recursive_mnt(mnt, mp); +} + +static int may_change_propagation(const struct mount *m) +{ + struct mnt_namespace *ns = m->mnt_ns; + + // it must be mounted in some namespace + if (IS_ERR_OR_NULL(ns)) // is_mounted() + return -EINVAL; + // and the caller must be admin in userns of that namespace + if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) + return -EPERM; + return 0; +} + +/* + * Sanity check the flags to change_mnt_propagation. + */ + +static int flags_to_propagation_type(int ms_flags) +{ + int type = ms_flags & ~(MS_REC | MS_SILENT); + + /* Fail if any non-propagation flags are set */ + if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) + return 0; + /* Only one propagation flag should be set */ + if (!is_power_of_2(type)) + return 0; + return type; +} + +/* + * recursively change the type of the mountpoint. + */ +static int do_change_type(const struct path *path, int ms_flags) +{ + struct mount *m; + struct mount *mnt = real_mount(path->mnt); + int recurse = ms_flags & MS_REC; + int type; + int err; + + if (!path_mounted(path)) + return -EINVAL; + + type = flags_to_propagation_type(ms_flags); + if (!type) + return -EINVAL; + + guard(namespace_excl)(); + + err = may_change_propagation(mnt); + if (err) + return err; + + if (type == MS_SHARED) { + err = invent_group_ids(mnt, recurse); + if (err) + return err; + } + + for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) + change_mnt_propagation(m, type); + + guard(mount_locked_reader)(); + touch_mnt_namespace(mnt->mnt_ns); + + return 0; +} + +/* may_copy_tree() - check if a mount tree can be copied + * @path: path to the mount tree to be copied + * + * This helper checks if the caller may copy the mount tree starting + * from @path->mnt. The caller may copy the mount tree under the + * following circumstances: + * + * (1) The caller is located in the mount namespace of the mount tree. + * This also implies that the mount does not belong to an anonymous + * mount namespace. + * (2) The caller tries to copy an nfs mount referring to a mount + * namespace, i.e., the caller is trying to copy a mount namespace + * entry from nsfs. + * (3) The caller tries to copy a pidfs mount referring to a pidfd. + * (4) The caller is trying to copy a mount tree that belongs to an + * anonymous mount namespace. + * + * For that to be safe, this helper enforces that the origin mount + * namespace the anonymous mount namespace was created from is the + * same as the caller's mount namespace by comparing the sequence + * numbers. + * + * This is not strictly necessary. The current semantics of the new + * mount api enforce that the caller must be located in the same + * mount namespace as the mount tree it interacts with. Using the + * origin sequence number preserves these semantics even for + * anonymous mount namespaces. However, one could envision extending + * the api to directly operate across mount namespace if needed. + * + * The ownership of a non-anonymous mount namespace such as the + * caller's cannot change. + * => We know that the caller's mount namespace is stable. + * + * If the origin sequence number of the anonymous mount namespace is + * the same as the sequence number of the caller's mount namespace. + * => The owning namespaces are the same. + * + * ==> The earlier capability check on the owning namespace of the + * caller's mount namespace ensures that the caller has the + * ability to copy the mount tree. + * + * Returns true if the mount tree can be copied, false otherwise. + */ +static inline bool may_copy_tree(const struct path *path) +{ + struct mount *mnt = real_mount(path->mnt); + const struct dentry_operations *d_op; + + if (check_mnt(mnt)) + return true; + + d_op = path->dentry->d_op; + if (d_op == &ns_dentry_operations) + return true; + + if (d_op == &pidfs_dentry_operations) + return true; + + if (!is_mounted(path->mnt)) + return false; + + return check_anonymous_mnt(mnt); +} + +static struct mount *__do_loopback(const struct path *old_path, + bool recurse, unsigned int copy_flags) +{ + struct mount *old = real_mount(old_path->mnt); + + if (IS_MNT_UNBINDABLE(old)) + return ERR_PTR(-EINVAL); + + if (!may_copy_tree(old_path)) + return ERR_PTR(-EINVAL); + + if (!recurse && __has_locked_children(old, old_path->dentry)) + return ERR_PTR(-EINVAL); + + if (recurse) + return copy_tree(old, old_path->dentry, copy_flags); + + return clone_mnt(old, old_path->dentry, copy_flags); +} + +/* + * do loopback mount. + */ +static int do_loopback(const struct path *path, const char *old_name, + int recurse) +{ + struct path old_path __free(path_put) = {}; + struct mount *mnt = NULL; + int err; + + if (!old_name || !*old_name) + return -EINVAL; + err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); + if (err) + return err; + + if (mnt_ns_loop(old_path.dentry)) + return -EINVAL; + + LOCK_MOUNT(mp, path); + if (IS_ERR(mp.parent)) + return PTR_ERR(mp.parent); + + if (!check_mnt(mp.parent)) + return -EINVAL; + + mnt = __do_loopback(&old_path, recurse, CL_COPY_MNT_NS_FILE); + if (IS_ERR(mnt)) + return PTR_ERR(mnt); + + err = graft_tree(mnt, &mp); + if (err) { + lock_mount_hash(); + umount_tree(mnt, UMOUNT_SYNC); + unlock_mount_hash(); + } + return err; +} + +static struct mnt_namespace *get_detached_copy(const struct path *path, unsigned int flags) +{ + struct mnt_namespace *ns, *mnt_ns = current->nsproxy->mnt_ns, *src_mnt_ns; + struct user_namespace *user_ns = mnt_ns->user_ns; + struct mount *mnt, *p; + + ns = alloc_mnt_ns(user_ns, true); + if (IS_ERR(ns)) + return ns; + + guard(namespace_excl)(); + + /* + * Record the sequence number of the source mount namespace. + * This needs to hold namespace_sem to ensure that the mount + * doesn't get attached. + */ + if (is_mounted(path->mnt)) { + src_mnt_ns = real_mount(path->mnt)->mnt_ns; + if (is_anon_ns(src_mnt_ns)) + ns->seq_origin = src_mnt_ns->seq_origin; + else + ns->seq_origin = src_mnt_ns->ns.ns_id; + } + + mnt = __do_loopback(path, (flags & AT_RECURSIVE), CL_COPY_MNT_NS_FILE); + if (IS_ERR(mnt)) { + emptied_ns = ns; + return ERR_CAST(mnt); + } + + for (p = mnt; p; p = next_mnt(p, mnt)) { + mnt_add_to_ns(ns, p); + ns->nr_mounts++; + } + ns->root = mnt; + return ns; +} + +static struct file *open_detached_copy(struct path *path, unsigned int flags) +{ + struct mnt_namespace *ns = get_detached_copy(path, flags); + struct file *file; + + if (IS_ERR(ns)) + return ERR_CAST(ns); + + mntput(path->mnt); + path->mnt = mntget(&ns->root->mnt); + file = dentry_open(path, O_PATH, current_cred()); + if (IS_ERR(file)) + dissolve_on_fput(path->mnt); + else + file->f_mode |= FMODE_NEED_UNMOUNT; + return file; +} + +enum mount_copy_flags_t { + MOUNT_COPY_RECURSIVE = (1 << 0), + MOUNT_COPY_NEW = (1 << 1), +}; + +static struct mnt_namespace *create_new_namespace(struct path *path, + enum mount_copy_flags_t flags) +{ + struct mnt_namespace *ns = current->nsproxy->mnt_ns; + struct user_namespace *user_ns = current_user_ns(); + struct mnt_namespace *new_ns; + struct mount *new_ns_root, *old_ns_root; + struct path to_path; + struct mount *mnt; + unsigned int copy_flags = 0; + bool locked = false, recurse = flags & MOUNT_COPY_RECURSIVE; + + if (unlikely(!d_can_lookup(path->dentry))) + return ERR_PTR(-ENOTDIR); + + if (user_ns != ns->user_ns) + copy_flags |= CL_SLAVE; + + new_ns = alloc_mnt_ns(user_ns, false); + if (IS_ERR(new_ns)) + return ERR_CAST(new_ns); + + old_ns_root = ns->root; + to_path.mnt = &old_ns_root->mnt; + to_path.dentry = old_ns_root->mnt.mnt_root; + + VFS_WARN_ON_ONCE(old_ns_root->mnt.mnt_sb->s_type != &nullfs_fs_type); + + LOCK_MOUNT_EXACT_COPY(mp, &to_path, copy_flags); + if (IS_ERR(mp.parent)) { + free_mnt_ns(new_ns); + return ERR_CAST(mp.parent); + } + new_ns_root = mp.parent; + + /* + * If the real rootfs had a locked mount on top of it somewhere + * in the stack, lock the new mount tree as well so it can't be + * exposed. + */ + mnt = old_ns_root; + while (mnt->overmount) { + mnt = mnt->overmount; + if (mnt->mnt.mnt_flags & MNT_LOCKED) + locked = true; + } + + /* + * We don't emulate unshare()ing a mount namespace. We stick to + * the restrictions of creating detached bind-mounts. It has a + * lot saner and simpler semantics. + */ + if (flags & MOUNT_COPY_NEW) + mnt = clone_mnt(real_mount(path->mnt), path->dentry, copy_flags); + else + mnt = __do_loopback(path, recurse, copy_flags); + scoped_guard(mount_writer) { + if (IS_ERR(mnt)) { + emptied_ns = new_ns; + umount_tree(new_ns_root, 0); + return ERR_CAST(mnt); + } + + if (locked) + mnt->mnt.mnt_flags |= MNT_LOCKED; + /* + * now mount the detached tree on top of the copy + * of the real rootfs we created. + */ + attach_mnt(mnt, new_ns_root, mp.mp); + if (user_ns != ns->user_ns) + lock_mnt_tree(new_ns_root); + } + + for (mnt = new_ns_root; mnt; mnt = next_mnt(mnt, new_ns_root)) { + mnt_add_to_ns(new_ns, mnt); + new_ns->nr_mounts++; + } + + new_ns->root = new_ns_root; + ns_tree_add_raw(new_ns); + return new_ns; +} + +static struct file *open_new_namespace(struct path *path, + enum mount_copy_flags_t flags) +{ + struct mnt_namespace *new_ns; + + new_ns = create_new_namespace(path, flags); + if (IS_ERR(new_ns)) + return ERR_CAST(new_ns); + return open_namespace_file(to_ns_common(new_ns)); +} + +static struct file *vfs_open_tree(int dfd, const char __user *filename, unsigned int flags) +{ + int ret; + struct path path __free(path_put) = {}; + int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW; + + BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC); + + if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE | + AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE | + OPEN_TREE_CLOEXEC | OPEN_TREE_NAMESPACE)) + return ERR_PTR(-EINVAL); + + if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE | OPEN_TREE_NAMESPACE)) == + AT_RECURSIVE) + return ERR_PTR(-EINVAL); + + if (hweight32(flags & (OPEN_TREE_CLONE | OPEN_TREE_NAMESPACE)) > 1) + return ERR_PTR(-EINVAL); + + if (flags & AT_NO_AUTOMOUNT) + lookup_flags &= ~LOOKUP_AUTOMOUNT; + if (flags & AT_SYMLINK_NOFOLLOW) + lookup_flags &= ~LOOKUP_FOLLOW; + + /* + * If we create a new mount namespace with the cloned mount tree we + * just care about being privileged over our current user namespace. + * The new mount namespace will be owned by it. + */ + if ((flags & OPEN_TREE_NAMESPACE) && + !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) + return ERR_PTR(-EPERM); + + if ((flags & OPEN_TREE_CLONE) && !may_mount()) + return ERR_PTR(-EPERM); + + CLASS(filename_uflags, name)(filename, flags); + ret = filename_lookup(dfd, name, lookup_flags, &path, NULL); + if (unlikely(ret)) + return ERR_PTR(ret); + + if (flags & OPEN_TREE_NAMESPACE) + return open_new_namespace(&path, (flags & AT_RECURSIVE) ? MOUNT_COPY_RECURSIVE : 0); + + if (flags & OPEN_TREE_CLONE) + return open_detached_copy(&path, flags); + + return dentry_open(&path, O_PATH, current_cred()); +} + +SYSCALL_DEFINE3(open_tree, int, dfd, const char __user *, filename, unsigned, flags) +{ + return FD_ADD(flags, vfs_open_tree(dfd, filename, flags)); +} + +/* + * Don't allow locked mount flags to be cleared. + * + * No locks need to be held here while testing the various MNT_LOCK + * flags because those flags can never be cleared once they are set. + */ +static bool can_change_locked_flags(struct mount *mnt, unsigned int mnt_flags) +{ + unsigned int fl = mnt->mnt.mnt_flags; + + if ((fl & MNT_LOCK_READONLY) && + !(mnt_flags & MNT_READONLY)) + return false; + + if ((fl & MNT_LOCK_NODEV) && + !(mnt_flags & MNT_NODEV)) + return false; + + if ((fl & MNT_LOCK_NOSUID) && + !(mnt_flags & MNT_NOSUID)) + return false; + + if ((fl & MNT_LOCK_NOEXEC) && + !(mnt_flags & MNT_NOEXEC)) + return false; + + if ((fl & MNT_LOCK_ATIME) && + ((fl & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK))) + return false; + + return true; +} + +static int change_mount_ro_state(struct mount *mnt, unsigned int mnt_flags) +{ + bool readonly_request = (mnt_flags & MNT_READONLY); + + if (readonly_request == __mnt_is_readonly(&mnt->mnt)) + return 0; + + if (readonly_request) + return mnt_make_readonly(mnt); + + mnt->mnt.mnt_flags &= ~MNT_READONLY; + return 0; +} + +static void set_mount_attributes(struct mount *mnt, unsigned int mnt_flags) +{ + mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK; + mnt->mnt.mnt_flags = mnt_flags; + touch_mnt_namespace(mnt->mnt_ns); +} + +static void mnt_warn_timestamp_expiry(const struct path *mountpoint, + struct vfsmount *mnt) +{ + struct super_block *sb = mnt->mnt_sb; + + if (!__mnt_is_readonly(mnt) && + (!(sb->s_iflags & SB_I_TS_EXPIRY_WARNED)) && + (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) { + char *buf, *mntpath; + + buf = __getname(); + if (buf) + mntpath = d_path(mountpoint, buf, PATH_MAX); + else + mntpath = ERR_PTR(-ENOMEM); + if (IS_ERR(mntpath)) + mntpath = "(unknown)"; + + pr_warn("%s filesystem being %s at %s supports timestamps until %ptTd (0x%llx)\n", + sb->s_type->name, + is_mounted(mnt) ? "remounted" : "mounted", + mntpath, &sb->s_time_max, + (unsigned long long)sb->s_time_max); + + sb->s_iflags |= SB_I_TS_EXPIRY_WARNED; + __putname(buf); + } +} + +/* + * Handle reconfiguration of the mountpoint only without alteration of the + * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND + * to mount(2). + */ +static int do_reconfigure_mnt(const struct path *path, unsigned int mnt_flags) +{ + struct super_block *sb = path->mnt->mnt_sb; + struct mount *mnt = real_mount(path->mnt); + int ret; + + if (!check_mnt(mnt)) + return -EINVAL; + + if (!path_mounted(path)) + return -EINVAL; + + if (!can_change_locked_flags(mnt, mnt_flags)) + return -EPERM; + + /* + * We're only checking whether the superblock is read-only not + * changing it, so only take down_read(&sb->s_umount). + */ + down_read(&sb->s_umount); + lock_mount_hash(); + ret = change_mount_ro_state(mnt, mnt_flags); + if (ret == 0) + set_mount_attributes(mnt, mnt_flags); + unlock_mount_hash(); + up_read(&sb->s_umount); + + mnt_warn_timestamp_expiry(path, &mnt->mnt); + + return ret; +} + +/* + * change filesystem flags. dir should be a physical root of filesystem. + * If you've mounted a non-root directory somewhere and want to do remount + * on it - tough luck. + */ +static int do_remount(const struct path *path, int sb_flags, + int mnt_flags, void *data) +{ + int err; + struct super_block *sb = path->mnt->mnt_sb; + struct mount *mnt = real_mount(path->mnt); + struct fs_context *fc; + + if (!check_mnt(mnt)) + return -EINVAL; + + if (!path_mounted(path)) + return -EINVAL; + + if (!can_change_locked_flags(mnt, mnt_flags)) + return -EPERM; + + fc = fs_context_for_reconfigure(path->dentry, sb_flags, MS_RMT_MASK); + if (IS_ERR(fc)) + return PTR_ERR(fc); + + /* + * Indicate to the filesystem that the remount request is coming + * from the legacy mount system call. + */ + fc->oldapi = true; + + err = parse_monolithic_mount_data(fc, data); + if (!err) { + down_write(&sb->s_umount); + err = -EPERM; + if (ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) { + err = reconfigure_super(fc); + if (!err) { + lock_mount_hash(); + set_mount_attributes(mnt, mnt_flags); + unlock_mount_hash(); + } + } + up_write(&sb->s_umount); + } + + mnt_warn_timestamp_expiry(path, &mnt->mnt); + + put_fs_context(fc); + return err; +} + +static inline int tree_contains_unbindable(struct mount *mnt) +{ + struct mount *p; + for (p = mnt; p; p = next_mnt(p, mnt)) { + if (IS_MNT_UNBINDABLE(p)) + return 1; + } + return 0; +} + +static int do_set_group(const struct path *from_path, const struct path *to_path) +{ + struct mount *from = real_mount(from_path->mnt); + struct mount *to = real_mount(to_path->mnt); + int err; + + guard(namespace_excl)(); + + err = may_change_propagation(from); + if (err) + return err; + err = may_change_propagation(to); + if (err) + return err; + + /* To and From paths should be mount roots */ + if (!path_mounted(from_path)) + return -EINVAL; + if (!path_mounted(to_path)) + return -EINVAL; + + /* Setting sharing groups is only allowed across same superblock */ + if (from->mnt.mnt_sb != to->mnt.mnt_sb) + return -EINVAL; + + /* From mount root should be wider than To mount root */ + if (!is_subdir(to->mnt.mnt_root, from->mnt.mnt_root)) + return -EINVAL; + + /* From mount should not have locked children in place of To's root */ + if (__has_locked_children(from, to->mnt.mnt_root)) + return -EINVAL; + + /* Setting sharing groups is only allowed on private mounts */ + if (IS_MNT_SHARED(to) || IS_MNT_SLAVE(to)) + return -EINVAL; + + /* From should not be private */ + if (!IS_MNT_SHARED(from) && !IS_MNT_SLAVE(from)) + return -EINVAL; + + if (IS_MNT_SLAVE(from)) { + hlist_add_behind(&to->mnt_slave, &from->mnt_slave); + to->mnt_master = from->mnt_master; + } + + if (IS_MNT_SHARED(from)) { + to->mnt_group_id = from->mnt_group_id; + list_add(&to->mnt_share, &from->mnt_share); + set_mnt_shared(to); + } + + guard(mount_locked_reader)(); + touch_mnt_namespace(to->mnt_ns); + + return 0; +} + +/** + * path_overmounted - check if path is overmounted + * @path: path to check + * + * Check if path is overmounted, i.e., if there's a mount on top of + * @path->mnt with @path->dentry as mountpoint. + * + * Context: namespace_sem must be held at least shared. + * MUST NOT be called under lock_mount_hash() (there one should just + * call __lookup_mnt() and check if it returns NULL). + * Return: If path is overmounted true is returned, false if not. + */ +static inline bool path_overmounted(const struct path *path) +{ + unsigned seq = read_seqbegin(&mount_lock); + bool no_child; + + rcu_read_lock(); + no_child = !__lookup_mnt(path->mnt, path->dentry); + rcu_read_unlock(); + if (need_seqretry(&mount_lock, seq)) { + read_seqlock_excl(&mount_lock); + no_child = !__lookup_mnt(path->mnt, path->dentry); + read_sequnlock_excl(&mount_lock); + } + return unlikely(!no_child); +} + +/* + * Check if there is a possibly empty chain of descent from p1 to p2. + * Locks: namespace_sem (shared) or mount_lock (read_seqlock_excl). + */ +static bool mount_is_ancestor(const struct mount *p1, const struct mount *p2) +{ + while (p2 != p1 && mnt_has_parent(p2)) + p2 = p2->mnt_parent; + return p2 == p1; +} + +/** + * can_move_mount_beneath - check that we can mount beneath the top mount + * @mnt_from: mount we are trying to move + * @mnt_to: mount under which to mount + * @mp: mountpoint of @mnt_to + * + * - Make sure that the caller can unmount the topmost mount ensuring + * that the caller could reveal the underlying mountpoint. + * - Ensure that nothing has been mounted on top of @mnt_from before we + * grabbed @namespace_sem to avoid creating pointless shadow mounts. + * - Prevent mounting beneath a mount if the propagation relationship + * between the source mount, parent mount, and top mount would lead to + * nonsensical mount trees. + * + * Context: This function expects namespace_lock() to be held. + * Return: On success 0, and on error a negative error code is returned. + */ +static int can_move_mount_beneath(const struct mount *mnt_from, + const struct mount *mnt_to, + struct pinned_mountpoint *mp) +{ + struct mount *parent_mnt_to = mnt_to->mnt_parent; + + /* Avoid creating shadow mounts during mount propagation. */ + if (mnt_from->overmount) + return -EINVAL; + + if (mount_is_ancestor(mnt_to, mnt_from)) + return -EINVAL; + + /* + * If the parent mount propagates to the child mount this would + * mean mounting @mnt_from on @mnt_to->mnt_parent and then + * propagating a copy @c of @mnt_from on top of @mnt_to. This + * defeats the whole purpose of mounting beneath another mount. + */ + if (propagation_would_overmount(parent_mnt_to, mnt_to, mp->mp)) + return -EINVAL; + + /* + * If @mnt_to->mnt_parent propagates to @mnt_from this would + * mean propagating a copy @c of @mnt_from on top of @mnt_from. + * Afterwards @mnt_from would be mounted on top of + * @mnt_to->mnt_parent and @mnt_to would be unmounted from + * @mnt->mnt_parent and remounted on @mnt_from. But since @c is + * already mounted on @mnt_from, @mnt_to would ultimately be + * remounted on top of @c. Afterwards, @mnt_from would be + * covered by a copy @c of @mnt_from and @c would be covered by + * @mnt_from itself. This defeats the whole purpose of mounting + * @mnt_from beneath @mnt_to. + */ + if (check_mnt(mnt_from) && + propagation_would_overmount(parent_mnt_to, mnt_from, mp->mp)) + return -EINVAL; + + return 0; +} + +/* may_use_mount() - check if a mount tree can be used + * @mnt: vfsmount to be used + * + * This helper checks if the caller may use the mount tree starting + * from @path->mnt. The caller may use the mount tree under the + * following circumstances: + * + * (1) The caller is located in the mount namespace of the mount tree. + * This also implies that the mount does not belong to an anonymous + * mount namespace. + * (2) The caller is trying to use a mount tree that belongs to an + * anonymous mount namespace. + * + * For that to be safe, this helper enforces that the origin mount + * namespace the anonymous mount namespace was created from is the + * same as the caller's mount namespace by comparing the sequence + * numbers. + * + * The ownership of a non-anonymous mount namespace such as the + * caller's cannot change. + * => We know that the caller's mount namespace is stable. + * + * If the origin sequence number of the anonymous mount namespace is + * the same as the sequence number of the caller's mount namespace. + * => The owning namespaces are the same. + * + * ==> The earlier capability check on the owning namespace of the + * caller's mount namespace ensures that the caller has the + * ability to use the mount tree. + * + * Returns true if the mount tree can be used, false otherwise. + */ +static inline bool may_use_mount(struct mount *mnt) +{ + if (check_mnt(mnt)) + return true; + + /* + * Make sure that noone unmounted the target path or somehow + * managed to get their hands on something purely kernel + * internal. + */ + if (!is_mounted(&mnt->mnt)) + return false; + + return check_anonymous_mnt(mnt); +} + +static int do_move_mount(const struct path *old_path, + const struct path *new_path, + enum mnt_tree_flags_t flags) +{ + struct mount *old = real_mount(old_path->mnt); + int err; + bool beneath = flags & MNT_TREE_BENEATH; + + if (!path_mounted(old_path)) + return -EINVAL; + + if (d_is_dir(new_path->dentry) != d_is_dir(old_path->dentry)) + return -EINVAL; + + LOCK_MOUNT_MAYBE_BENEATH(mp, new_path, beneath); + if (IS_ERR(mp.parent)) + return PTR_ERR(mp.parent); + + if (check_mnt(old)) { + /* if the source is in our namespace... */ + /* ... it should be detachable from parent */ + if (!mnt_has_parent(old) || IS_MNT_LOCKED(old)) + return -EINVAL; + /* ... which should not be shared */ + if (IS_MNT_SHARED(old->mnt_parent)) + return -EINVAL; + /* ... and the target should be in our namespace */ + if (!check_mnt(mp.parent)) + return -EINVAL; + } else { + /* + * otherwise the source must be the root of some anon namespace. + */ + if (!anon_ns_root(old)) + return -EINVAL; + /* + * Bail out early if the target is within the same namespace - + * subsequent checks would've rejected that, but they lose + * some corner cases if we check it early. + */ + if (old->mnt_ns == mp.parent->mnt_ns) + return -EINVAL; + /* + * Target should be either in our namespace or in an acceptable + * anon namespace, sensu check_anonymous_mnt(). + */ + if (!may_use_mount(mp.parent)) + return -EINVAL; + } + + if (beneath) { + struct mount *over = real_mount(new_path->mnt); + + if (mp.parent != over->mnt_parent) + over = mp.parent->overmount; + err = can_move_mount_beneath(old, over, &mp); + if (err) + return err; + } + + /* + * Don't move a mount tree containing unbindable mounts to a destination + * mount which is shared. + */ + if (IS_MNT_SHARED(mp.parent) && tree_contains_unbindable(old)) + return -EINVAL; + if (!check_for_nsfs_mounts(old)) + return -ELOOP; + if (mount_is_ancestor(old, mp.parent)) + return -ELOOP; + + return attach_recursive_mnt(old, &mp); +} + +static int do_move_mount_old(const struct path *path, const char *old_name) +{ + struct path old_path __free(path_put) = {}; + int err; + + if (!old_name || !*old_name) + return -EINVAL; + + err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); + if (err) + return err; + + return do_move_mount(&old_path, path, 0); +} + +/* + * add a mount into a namespace's mount tree + */ +static int do_add_mount(struct mount *newmnt, const struct pinned_mountpoint *mp, + int mnt_flags) +{ + struct mount *parent = mp->parent; + + if (IS_ERR(parent)) + return PTR_ERR(parent); + + mnt_flags &= ~MNT_INTERNAL_FLAGS; + + if (unlikely(!check_mnt(parent))) { + /* that's acceptable only for automounts done in private ns */ + if (!(mnt_flags & MNT_SHRINKABLE)) + return -EINVAL; + /* ... and for those we'd better have mountpoint still alive */ + if (!parent->mnt_ns) + return -EINVAL; + } + + /* Refuse the same filesystem on the same mount point */ + if (parent->mnt.mnt_sb == newmnt->mnt.mnt_sb && + parent->mnt.mnt_root == mp->mp->m_dentry) + return -EBUSY; + + if (d_is_symlink(newmnt->mnt.mnt_root)) + return -EINVAL; + + newmnt->mnt.mnt_flags = mnt_flags; + return graft_tree(newmnt, mp); +} + +static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags); + +/* + * Create a new mount using a superblock configuration and request it + * be added to the namespace tree. + */ +static int do_new_mount_fc(struct fs_context *fc, const struct path *mountpoint, + unsigned int mnt_flags) +{ + struct super_block *sb; + struct vfsmount *mnt __free(mntput) = fc_mount(fc); + int error; + + if (IS_ERR(mnt)) + return PTR_ERR(mnt); + + sb = fc->root->d_sb; + error = security_sb_kern_mount(sb); + if (unlikely(error)) + return error; + + if (unlikely(mount_too_revealing(sb, &mnt_flags))) { + errorfcp(fc, "VFS", "Mount too revealing"); + return -EPERM; + } + + mnt_warn_timestamp_expiry(mountpoint, mnt); + + LOCK_MOUNT(mp, mountpoint); + error = do_add_mount(real_mount(mnt), &mp, mnt_flags); + if (!error) + retain_and_null_ptr(mnt); // consumed on success + return error; +} + +/* + * create a new mount for userspace and request it to be added into the + * namespace's tree + */ +static int do_new_mount(const struct path *path, const char *fstype, + int sb_flags, int mnt_flags, + const char *name, void *data) +{ + struct file_system_type *type; + struct fs_context *fc; + const char *subtype = NULL; + int err = 0; + + if (!fstype) + return -EINVAL; + + type = get_fs_type(fstype); + if (!type) + return -ENODEV; + + if (type->fs_flags & FS_HAS_SUBTYPE) { + subtype = strchr(fstype, '.'); + if (subtype) { + subtype++; + if (!*subtype) { + put_filesystem(type); + return -EINVAL; + } + } + } + + fc = fs_context_for_mount(type, sb_flags); + put_filesystem(type); + if (IS_ERR(fc)) + return PTR_ERR(fc); + + /* + * Indicate to the filesystem that the mount request is coming + * from the legacy mount system call. + */ + fc->oldapi = true; + + if (subtype) + err = vfs_parse_fs_string(fc, "subtype", subtype); + if (!err && name) + err = vfs_parse_fs_string(fc, "source", name); + if (!err) + err = parse_monolithic_mount_data(fc, data); + if (!err && !mount_capable(fc)) + err = -EPERM; + if (!err) + err = do_new_mount_fc(fc, path, mnt_flags); + + put_fs_context(fc); + return err; +} + +static void lock_mount_exact(const struct path *path, + struct pinned_mountpoint *mp, bool copy_mount, + unsigned int copy_flags) +{ + struct dentry *dentry = path->dentry; + int err; + + /* Assert that inode_lock() locked the correct inode. */ + VFS_WARN_ON_ONCE(copy_mount && !path_mounted(path)); + + inode_lock(dentry->d_inode); + namespace_lock(); + if (unlikely(cant_mount(dentry))) + err = -ENOENT; + else if (!copy_mount && path_overmounted(path)) + err = -EBUSY; + else + err = get_mountpoint(dentry, mp); + if (unlikely(err)) { + namespace_unlock(); + inode_unlock(dentry->d_inode); + mp->parent = ERR_PTR(err); + return; + } + + if (copy_mount) + mp->parent = clone_mnt(real_mount(path->mnt), dentry, copy_flags); + else + mp->parent = real_mount(path->mnt); + if (unlikely(IS_ERR(mp->parent))) + __unlock_mount(mp); +} + +int finish_automount(struct vfsmount *__m, const struct path *path) +{ + struct vfsmount *m __free(mntput) = __m; + struct mount *mnt; + int err; + + if (!m) + return 0; + if (IS_ERR(m)) + return PTR_ERR(m); + + mnt = real_mount(m); + + if (m->mnt_root == path->dentry) + return -ELOOP; + + /* + * we don't want to use LOCK_MOUNT() - in this case finding something + * that overmounts our mountpoint to be means "quitely drop what we've + * got", not "try to mount it on top". + */ + LOCK_MOUNT_EXACT(mp, path); + if (mp.parent == ERR_PTR(-EBUSY)) + return 0; + + err = do_add_mount(mnt, &mp, path->mnt->mnt_flags | MNT_SHRINKABLE); + if (likely(!err)) + retain_and_null_ptr(m); + return err; +} + +/** + * mnt_set_expiry - Put a mount on an expiration list + * @mnt: The mount to list. + * @expiry_list: The list to add the mount to. + */ +void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) +{ + guard(mount_locked_reader)(); + list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); +} +EXPORT_SYMBOL(mnt_set_expiry); + +/* + * process a list of expirable mountpoints with the intent of discarding any + * mountpoints that aren't in use and haven't been touched since last we came + * here + */ +void mark_mounts_for_expiry(struct list_head *mounts) +{ + struct mount *mnt, *next; + LIST_HEAD(graveyard); + + if (list_empty(mounts)) + return; + + guard(namespace_excl)(); + guard(mount_writer)(); + + /* extract from the expiration list every vfsmount that matches the + * following criteria: + * - already mounted + * - only referenced by its parent vfsmount + * - still marked for expiry (marked on the last call here; marks are + * cleared by mntput()) + */ + list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { + if (!is_mounted(&mnt->mnt)) + continue; + if (!xchg(&mnt->mnt_expiry_mark, 1) || + propagate_mount_busy(mnt, 1)) + continue; + list_move(&mnt->mnt_expire, &graveyard); + } + while (!list_empty(&graveyard)) { + mnt = list_first_entry(&graveyard, struct mount, mnt_expire); + touch_mnt_namespace(mnt->mnt_ns); + umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); + } +} + +EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); + +/* + * Ripoff of 'select_parent()' + * + * search the list of submounts for a given mountpoint, and move any + * shrinkable submounts to the 'graveyard' list. + */ +static int select_submounts(struct mount *parent, struct list_head *graveyard) +{ + struct mount *this_parent = parent; + struct list_head *next; + int found = 0; + +repeat: + next = this_parent->mnt_mounts.next; +resume: + while (next != &this_parent->mnt_mounts) { + struct list_head *tmp = next; + struct mount *mnt = list_entry(tmp, struct mount, mnt_child); + + next = tmp->next; + if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) + continue; + /* + * Descend a level if the d_mounts list is non-empty. + */ + if (!list_empty(&mnt->mnt_mounts)) { + this_parent = mnt; + goto repeat; + } + + if (!propagate_mount_busy(mnt, 1)) { + list_move_tail(&mnt->mnt_expire, graveyard); + found++; + } + } + /* + * All done at this level ... ascend and resume the search + */ + if (this_parent != parent) { + next = this_parent->mnt_child.next; + this_parent = this_parent->mnt_parent; + goto resume; + } + return found; +} + +/* + * process a list of expirable mountpoints with the intent of discarding any + * submounts of a specific parent mountpoint + * + * mount_lock must be held for write + */ +static void shrink_submounts(struct mount *mnt) +{ + LIST_HEAD(graveyard); + struct mount *m; + + /* extract submounts of 'mountpoint' from the expiration list */ + while (select_submounts(mnt, &graveyard)) { + while (!list_empty(&graveyard)) { + m = list_first_entry(&graveyard, struct mount, + mnt_expire); + touch_mnt_namespace(m->mnt_ns); + umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC); + } + } +} + +static void *copy_mount_options(const void __user * data) +{ + char *copy; + unsigned left, offset; + + if (!data) + return NULL; + + copy = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!copy) + return ERR_PTR(-ENOMEM); + + left = copy_from_user(copy, data, PAGE_SIZE); + + /* + * Not all architectures have an exact copy_from_user(). Resort to + * byte at a time. + */ + offset = PAGE_SIZE - left; + while (left) { + char c; + if (get_user(c, (const char __user *)data + offset)) + break; + copy[offset] = c; + left--; + offset++; + } + + if (left == PAGE_SIZE) { + kfree(copy); + return ERR_PTR(-EFAULT); + } + + return copy; +} + +static char *copy_mount_string(const void __user *data) +{ + return data ? strndup_user(data, PATH_MAX) : NULL; +} + +/* + * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to + * be given to the mount() call (ie: read-only, no-dev, no-suid etc). + * + * data is a (void *) that can point to any structure up to + * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent + * information (or be NULL). + * + * Pre-0.97 versions of mount() didn't have a flags word. + * When the flags word was introduced its top half was required + * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. + * Therefore, if this magic number is present, it carries no information + * and must be discarded. + */ +int path_mount(const char *dev_name, const struct path *path, + const char *type_page, unsigned long flags, void *data_page) +{ + unsigned int mnt_flags = 0, sb_flags; + int ret; + + /* Discard magic */ + if ((flags & MS_MGC_MSK) == MS_MGC_VAL) + flags &= ~MS_MGC_MSK; + + /* Basic sanity checks */ + if (data_page) + ((char *)data_page)[PAGE_SIZE - 1] = 0; + + if (flags & MS_NOUSER) + return -EINVAL; + + ret = security_sb_mount(dev_name, path, type_page, flags, data_page); + if (ret) + return ret; + if (!may_mount()) + return -EPERM; + if (flags & SB_MANDLOCK) + warn_mandlock(); + + /* Default to relatime unless overriden */ + if (!(flags & MS_NOATIME)) + mnt_flags |= MNT_RELATIME; + + /* Separate the per-mountpoint flags */ + if (flags & MS_NOSUID) + mnt_flags |= MNT_NOSUID; + if (flags & MS_NODEV) + mnt_flags |= MNT_NODEV; + if (flags & MS_NOEXEC) + mnt_flags |= MNT_NOEXEC; + if (flags & MS_NOATIME) + mnt_flags |= MNT_NOATIME; + if (flags & MS_NODIRATIME) + mnt_flags |= MNT_NODIRATIME; + if (flags & MS_STRICTATIME) + mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); + if (flags & MS_RDONLY) + mnt_flags |= MNT_READONLY; + if (flags & MS_NOSYMFOLLOW) + mnt_flags |= MNT_NOSYMFOLLOW; + + /* The default atime for remount is preservation */ + if ((flags & MS_REMOUNT) && + ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME | + MS_STRICTATIME)) == 0)) { + mnt_flags &= ~MNT_ATIME_MASK; + mnt_flags |= path->mnt->mnt_flags & MNT_ATIME_MASK; + } + + sb_flags = flags & (SB_RDONLY | + SB_SYNCHRONOUS | + SB_MANDLOCK | + SB_DIRSYNC | + SB_SILENT | + SB_POSIXACL | + SB_LAZYTIME | + SB_I_VERSION); + + if ((flags & (MS_REMOUNT | MS_BIND)) == (MS_REMOUNT | MS_BIND)) + return do_reconfigure_mnt(path, mnt_flags); + if (flags & MS_REMOUNT) + return do_remount(path, sb_flags, mnt_flags, data_page); + if (flags & MS_BIND) + return do_loopback(path, dev_name, flags & MS_REC); + if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) + return do_change_type(path, flags); + if (flags & MS_MOVE) + return do_move_mount_old(path, dev_name); + + return do_new_mount(path, type_page, sb_flags, mnt_flags, dev_name, + data_page); +} + +int do_mount(const char *dev_name, const char __user *dir_name, + const char *type_page, unsigned long flags, void *data_page) +{ + struct path path __free(path_put) = {}; + int ret; + + ret = user_path_at(AT_FDCWD, dir_name, LOOKUP_FOLLOW, &path); + if (ret) + return ret; + return path_mount(dev_name, &path, type_page, flags, data_page); +} + +static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns) +{ + return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES); +} + +static void dec_mnt_namespaces(struct ucounts *ucounts) +{ + dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES); +} + +static void free_mnt_ns(struct mnt_namespace *ns) +{ + if (!is_anon_ns(ns)) + ns_common_free(ns); + dec_mnt_namespaces(ns->ucounts); + mnt_ns_tree_remove(ns); +} + +static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool anon) +{ + struct mnt_namespace *new_ns; + struct ucounts *ucounts; + int ret; + + ucounts = inc_mnt_namespaces(user_ns); + if (!ucounts) + return ERR_PTR(-ENOSPC); + + new_ns = kzalloc_obj(struct mnt_namespace, GFP_KERNEL_ACCOUNT); + if (!new_ns) { + dec_mnt_namespaces(ucounts); + return ERR_PTR(-ENOMEM); + } + + if (anon) + ret = ns_common_init_inum(new_ns, MNT_NS_ANON_INO); + else + ret = ns_common_init(new_ns); + if (ret) { + kfree(new_ns); + dec_mnt_namespaces(ucounts); + return ERR_PTR(ret); + } + ns_tree_gen_id(new_ns); + + new_ns->is_anon = anon; + refcount_set(&new_ns->passive, 1); + new_ns->mounts = RB_ROOT; + init_waitqueue_head(&new_ns->poll); + new_ns->user_ns = get_user_ns(user_ns); + new_ns->ucounts = ucounts; + return new_ns; +} + +__latent_entropy +struct mnt_namespace *copy_mnt_ns(u64 flags, struct mnt_namespace *ns, + struct user_namespace *user_ns, struct fs_struct *new_fs) +{ + struct mnt_namespace *new_ns; + struct path old_root __free(path_put) = {}; + struct path old_pwd __free(path_put) = {}; + struct mount *p, *q; + struct mount *old; + struct mount *new; + int copy_flags; + + BUG_ON(!ns); + + if (likely(!(flags & CLONE_NEWNS))) { + get_mnt_ns(ns); + return ns; + } + + old = ns->root; + + new_ns = alloc_mnt_ns(user_ns, false); + if (IS_ERR(new_ns)) + return new_ns; + + guard(namespace_excl)(); + + if (flags & CLONE_EMPTY_MNTNS) + copy_flags = 0; + else + copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE; + if (user_ns != ns->user_ns) + copy_flags |= CL_SLAVE; + + if (flags & CLONE_EMPTY_MNTNS) + new = clone_mnt(old, old->mnt.mnt_root, copy_flags); + else + new = copy_tree(old, old->mnt.mnt_root, copy_flags); + if (IS_ERR(new)) { + emptied_ns = new_ns; + return ERR_CAST(new); + } + if (user_ns != ns->user_ns) { + guard(mount_writer)(); + lock_mnt_tree(new); + } + new_ns->root = new; + + if (flags & CLONE_EMPTY_MNTNS) { + /* + * Empty mount namespace: only the root mount exists. + * Reset root and pwd to the cloned mount's root dentry. + */ + if (new_fs) { + old_root = new_fs->root; + old_pwd = new_fs->pwd; + + new_fs->root.mnt = mntget(&new->mnt); + new_fs->root.dentry = dget(new->mnt.mnt_root); + + new_fs->pwd.mnt = mntget(&new->mnt); + new_fs->pwd.dentry = dget(new->mnt.mnt_root); + } + mnt_add_to_ns(new_ns, new); + new_ns->nr_mounts++; + } else { + /* + * Full copy: walk old and new trees in parallel, switching + * the tsk->fs->* elements and marking new vfsmounts as + * belonging to new namespace. We have already acquired a + * private fs_struct, so tsk->fs->lock is not needed. + */ + p = old; + q = new; + while (p) { + mnt_add_to_ns(new_ns, q); + new_ns->nr_mounts++; + if (new_fs) { + if (&p->mnt == new_fs->root.mnt) { + old_root.mnt = new_fs->root.mnt; + new_fs->root.mnt = mntget(&q->mnt); + } + if (&p->mnt == new_fs->pwd.mnt) { + old_pwd.mnt = new_fs->pwd.mnt; + new_fs->pwd.mnt = mntget(&q->mnt); + } + } + p = next_mnt(p, old); + q = next_mnt(q, new); + if (!q) + break; + // an mntns binding we'd skipped? + while (p->mnt.mnt_root != q->mnt.mnt_root) + p = next_mnt(skip_mnt_tree(p), old); + } + } + ns_tree_add_raw(new_ns); + return new_ns; +} + +struct dentry *mount_subtree(struct vfsmount *m, const char *name) +{ + struct mount *mnt = real_mount(m); + struct mnt_namespace *ns; + struct super_block *s; + struct path path; + int err; + + ns = alloc_mnt_ns(&init_user_ns, true); + if (IS_ERR(ns)) { + mntput(m); + return ERR_CAST(ns); + } + ns->root = mnt; + ns->nr_mounts++; + mnt_add_to_ns(ns, mnt); + + err = vfs_path_lookup(m->mnt_root, m, + name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); + + put_mnt_ns(ns); + + if (err) + return ERR_PTR(err); + + /* trade a vfsmount reference for active sb one */ + s = path.mnt->mnt_sb; + atomic_inc(&s->s_active); + mntput(path.mnt); + /* lock the sucker */ + down_write(&s->s_umount); + /* ... and return the root of (sub)tree on it */ + return path.dentry; +} +EXPORT_SYMBOL(mount_subtree); + +SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, + char __user *, type, unsigned long, flags, void __user *, data) +{ + int ret; + char *kernel_type; + char *kernel_dev; + void *options; + + kernel_type = copy_mount_string(type); + ret = PTR_ERR(kernel_type); + if (IS_ERR(kernel_type)) + goto out_type; + + kernel_dev = copy_mount_string(dev_name); + ret = PTR_ERR(kernel_dev); + if (IS_ERR(kernel_dev)) + goto out_dev; + + options = copy_mount_options(data); + ret = PTR_ERR(options); + if (IS_ERR(options)) + goto out_data; + + ret = do_mount(kernel_dev, dir_name, kernel_type, flags, options); + + kfree(options); +out_data: + kfree(kernel_dev); +out_dev: + kfree(kernel_type); +out_type: + return ret; +} + +#define FSMOUNT_VALID_FLAGS \ + (MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \ + MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \ + MOUNT_ATTR_NOSYMFOLLOW) + +#define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP) + +#define MOUNT_SETATTR_PROPAGATION_FLAGS \ + (MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED) + +static unsigned int attr_flags_to_mnt_flags(u64 attr_flags) +{ + unsigned int mnt_flags = 0; + + if (attr_flags & MOUNT_ATTR_RDONLY) + mnt_flags |= MNT_READONLY; + if (attr_flags & MOUNT_ATTR_NOSUID) + mnt_flags |= MNT_NOSUID; + if (attr_flags & MOUNT_ATTR_NODEV) + mnt_flags |= MNT_NODEV; + if (attr_flags & MOUNT_ATTR_NOEXEC) + mnt_flags |= MNT_NOEXEC; + if (attr_flags & MOUNT_ATTR_NODIRATIME) + mnt_flags |= MNT_NODIRATIME; + if (attr_flags & MOUNT_ATTR_NOSYMFOLLOW) + mnt_flags |= MNT_NOSYMFOLLOW; + + return mnt_flags; +} + +/* + * Create a kernel mount representation for a new, prepared superblock + * (specified by fs_fd) and attach to an open_tree-like file descriptor. + */ +SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags, + unsigned int, attr_flags) +{ + struct path new_path __free(path_put) = {}; + struct mnt_namespace *ns; + struct fs_context *fc; + struct vfsmount *new_mnt; + struct mount *mnt; + unsigned int mnt_flags = 0; + long ret; + + if ((flags & ~(FSMOUNT_CLOEXEC | FSMOUNT_NAMESPACE)) != 0) + return -EINVAL; + + if ((flags & FSMOUNT_NAMESPACE) && + !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) + return -EPERM; + + if (!(flags & FSMOUNT_NAMESPACE) && !may_mount()) + return -EPERM; + + if (attr_flags & ~FSMOUNT_VALID_FLAGS) + return -EINVAL; + + mnt_flags = attr_flags_to_mnt_flags(attr_flags); + + switch (attr_flags & MOUNT_ATTR__ATIME) { + case MOUNT_ATTR_STRICTATIME: + break; + case MOUNT_ATTR_NOATIME: + mnt_flags |= MNT_NOATIME; + break; + case MOUNT_ATTR_RELATIME: + mnt_flags |= MNT_RELATIME; + break; + default: + return -EINVAL; + } + + CLASS(fd, f)(fs_fd); + if (fd_empty(f)) + return -EBADF; + + if (fd_file(f)->f_op != &fscontext_fops) + return -EINVAL; + + fc = fd_file(f)->private_data; + + ACQUIRE(mutex_intr, uapi_mutex)(&fc->uapi_mutex); + ret = ACQUIRE_ERR(mutex_intr, &uapi_mutex); + if (ret) + return ret; + + /* There must be a valid superblock or we can't mount it */ + ret = -EINVAL; + if (!fc->root) + return ret; + + ret = -EPERM; + if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) { + errorfcp(fc, "VFS", "Mount too revealing"); + return ret; + } + + ret = -EBUSY; + if (fc->phase != FS_CONTEXT_AWAITING_MOUNT) + return ret; + + if (fc->sb_flags & SB_MANDLOCK) + warn_mandlock(); + + new_mnt = vfs_create_mount(fc); + if (IS_ERR(new_mnt)) + return PTR_ERR(new_mnt); + if (new_mnt->mnt_sb->s_flags & SB_NOUSER) { + mntput(new_mnt); + return -EINVAL; + } + new_mnt->mnt_flags = mnt_flags; + + new_path.dentry = dget(fc->root); + new_path.mnt = new_mnt; + + /* We've done the mount bit - now move the file context into more or + * less the same state as if we'd done an fspick(). We don't want to + * do any memory allocation or anything like that at this point as we + * don't want to have to handle any errors incurred. + */ + vfs_clean_context(fc); + + if (flags & FSMOUNT_NAMESPACE) + return FD_ADD((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0, + open_new_namespace(&new_path, MOUNT_COPY_NEW)); + + ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true); + if (IS_ERR(ns)) + return PTR_ERR(ns); + mnt = real_mount(new_path.mnt); + ns->root = mnt; + ns->nr_mounts = 1; + mnt_add_to_ns(ns, mnt); + mntget(new_path.mnt); + + FD_PREPARE(fdf, (flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0, + dentry_open(&new_path, O_PATH, fc->cred)); + if (fdf.err) { + dissolve_on_fput(new_path.mnt); + return fdf.err; + } + + /* + * Attach to an apparent O_PATH fd with a note that we + * need to unmount it, not just simply put it. + */ + fd_prepare_file(fdf)->f_mode |= FMODE_NEED_UNMOUNT; + return fd_publish(fdf); +} + +static inline int vfs_move_mount(const struct path *from_path, + const struct path *to_path, + enum mnt_tree_flags_t mflags) +{ + int ret; + + ret = security_move_mount(from_path, to_path); + if (ret) + return ret; + + if (mflags & MNT_TREE_PROPAGATION) + return do_set_group(from_path, to_path); + + return do_move_mount(from_path, to_path, mflags); +} + +/* + * Move a mount from one place to another. In combination with + * fsopen()/fsmount() this is used to install a new mount and in combination + * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy + * a mount subtree. + * + * Note the flags value is a combination of MOVE_MOUNT_* flags. + */ +SYSCALL_DEFINE5(move_mount, + int, from_dfd, const char __user *, from_pathname, + int, to_dfd, const char __user *, to_pathname, + unsigned int, flags) +{ + struct path to_path __free(path_put) = {}; + struct path from_path __free(path_put) = {}; + unsigned int lflags, uflags; + enum mnt_tree_flags_t mflags = 0; + int ret = 0; + + if (!may_mount()) + return -EPERM; + + if (flags & ~MOVE_MOUNT__MASK) + return -EINVAL; + + if ((flags & (MOVE_MOUNT_BENEATH | MOVE_MOUNT_SET_GROUP)) == + (MOVE_MOUNT_BENEATH | MOVE_MOUNT_SET_GROUP)) + return -EINVAL; + + if (flags & MOVE_MOUNT_SET_GROUP) mflags |= MNT_TREE_PROPAGATION; + if (flags & MOVE_MOUNT_BENEATH) mflags |= MNT_TREE_BENEATH; + + uflags = 0; + if (flags & MOVE_MOUNT_T_EMPTY_PATH) + uflags = AT_EMPTY_PATH; + + CLASS(filename_maybe_null,to_name)(to_pathname, uflags); + if (!to_name && to_dfd >= 0) { + CLASS(fd_raw, f_to)(to_dfd); + if (fd_empty(f_to)) + return -EBADF; + + to_path = fd_file(f_to)->f_path; + path_get(&to_path); + } else { + lflags = 0; + if (flags & MOVE_MOUNT_T_SYMLINKS) + lflags |= LOOKUP_FOLLOW; + if (flags & MOVE_MOUNT_T_AUTOMOUNTS) + lflags |= LOOKUP_AUTOMOUNT; + ret = filename_lookup(to_dfd, to_name, lflags, &to_path, NULL); + if (ret) + return ret; + } + + uflags = 0; + if (flags & MOVE_MOUNT_F_EMPTY_PATH) + uflags = AT_EMPTY_PATH; + + CLASS(filename_maybe_null,from_name)(from_pathname, uflags); + if (!from_name && from_dfd >= 0) { + CLASS(fd_raw, f_from)(from_dfd); + if (fd_empty(f_from)) + return -EBADF; + + return vfs_move_mount(&fd_file(f_from)->f_path, &to_path, mflags); + } + + lflags = 0; + if (flags & MOVE_MOUNT_F_SYMLINKS) + lflags |= LOOKUP_FOLLOW; + if (flags & MOVE_MOUNT_F_AUTOMOUNTS) + lflags |= LOOKUP_AUTOMOUNT; + ret = filename_lookup(from_dfd, from_name, lflags, &from_path, NULL); + if (ret) + return ret; + + return vfs_move_mount(&from_path, &to_path, mflags); +} + +/* + * Return true if path is reachable from root + * + * locks: mount_locked_reader || namespace_shared && is_mounted(mnt) + */ +bool is_path_reachable(struct mount *mnt, struct dentry *dentry, + const struct path *root) +{ + while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { + dentry = mnt->mnt_mountpoint; + mnt = mnt->mnt_parent; + } + return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); +} + +bool path_is_under(const struct path *path1, const struct path *path2) +{ + guard(mount_locked_reader)(); + return is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); +} +EXPORT_SYMBOL(path_is_under); + +int path_pivot_root(struct path *new, struct path *old) +{ + struct path root __free(path_put) = {}; + struct mount *new_mnt, *root_mnt, *old_mnt, *root_parent, *ex_parent; + int error; + + if (!may_mount()) + return -EPERM; + + error = security_sb_pivotroot(old, new); + if (error) + return error; + + get_fs_root(current->fs, &root); + + LOCK_MOUNT(old_mp, old); + old_mnt = old_mp.parent; + if (IS_ERR(old_mnt)) + return PTR_ERR(old_mnt); + + new_mnt = real_mount(new->mnt); + root_mnt = real_mount(root.mnt); + ex_parent = new_mnt->mnt_parent; + root_parent = root_mnt->mnt_parent; + if (IS_MNT_SHARED(old_mnt) || + IS_MNT_SHARED(ex_parent) || + IS_MNT_SHARED(root_parent)) + return -EINVAL; + if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) + return -EINVAL; + if (new_mnt->mnt.mnt_flags & MNT_LOCKED) + return -EINVAL; + if (d_unlinked(new->dentry)) + return -ENOENT; + if (new_mnt == root_mnt || old_mnt == root_mnt) + return -EBUSY; /* loop, on the same file system */ + if (!path_mounted(&root)) + return -EINVAL; /* not a mountpoint */ + if (!mnt_has_parent(root_mnt)) + return -EINVAL; /* absolute root */ + if (!path_mounted(new)) + return -EINVAL; /* not a mountpoint */ + if (!mnt_has_parent(new_mnt)) + return -EINVAL; /* absolute root */ + /* make sure we can reach put_old from new_root */ + if (!is_path_reachable(old_mnt, old_mp.mp->m_dentry, new)) + return -EINVAL; + /* make certain new is below the root */ + if (!is_path_reachable(new_mnt, new->dentry, &root)) + return -EINVAL; + lock_mount_hash(); + umount_mnt(new_mnt); + if (root_mnt->mnt.mnt_flags & MNT_LOCKED) { + new_mnt->mnt.mnt_flags |= MNT_LOCKED; + root_mnt->mnt.mnt_flags &= ~MNT_LOCKED; + } + /* mount new_root on / */ + attach_mnt(new_mnt, root_parent, root_mnt->mnt_mp); + umount_mnt(root_mnt); + /* mount old root on put_old */ + attach_mnt(root_mnt, old_mnt, old_mp.mp); + touch_mnt_namespace(current->nsproxy->mnt_ns); + /* A moved mount should not expire automatically */ + list_del_init(&new_mnt->mnt_expire); + unlock_mount_hash(); + mnt_notify_add(root_mnt); + mnt_notify_add(new_mnt); + chroot_fs_refs(&root, new); + return 0; +} + +/* + * pivot_root Semantics: + * Moves the root file system of the current process to the directory put_old, + * makes new_root as the new root file system of the current process, and sets + * root/cwd of all processes which had them on the current root to new_root. + * + * Restrictions: + * The new_root and put_old must be directories, and must not be on the + * same file system as the current process root. The put_old must be + * underneath new_root, i.e. adding a non-zero number of /.. to the string + * pointed to by put_old must yield the same directory as new_root. No other + * file system may be mounted on put_old. After all, new_root is a mountpoint. + * + * The immutable nullfs filesystem is mounted as the true root of the VFS + * hierarchy. The mutable rootfs (tmpfs/ramfs) is layered on top of this, + * allowing pivot_root() to work normally from initramfs. + * + * Notes: + * - we don't move root/cwd if they are not at the root (reason: if something + * cared enough to change them, it's probably wrong to force them elsewhere) + * - it's okay to pick a root that isn't the root of a file system, e.g. + * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, + * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root + * first. + */ +SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, + const char __user *, put_old) +{ + struct path new __free(path_put) = {}; + struct path old __free(path_put) = {}; + int error; + + error = user_path_at(AT_FDCWD, new_root, + LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &new); + if (error) + return error; + + error = user_path_at(AT_FDCWD, put_old, + LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old); + if (error) + return error; + + return path_pivot_root(&new, &old); +} + +static unsigned int recalc_flags(struct mount_kattr *kattr, struct mount *mnt) +{ + unsigned int flags = mnt->mnt.mnt_flags; + + /* flags to clear */ + flags &= ~kattr->attr_clr; + /* flags to raise */ + flags |= kattr->attr_set; + + return flags; +} + +static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) +{ + struct vfsmount *m = &mnt->mnt; + struct user_namespace *fs_userns = m->mnt_sb->s_user_ns; + + if (!kattr->mnt_idmap) + return 0; + + /* + * Creating an idmapped mount with the filesystem wide idmapping + * doesn't make sense so block that. We don't allow mushy semantics. + */ + if (kattr->mnt_userns == m->mnt_sb->s_user_ns) + return -EINVAL; + + /* + * We only allow an mount to change it's idmapping if it has + * never been accessible to userspace. + */ + if (!(kattr->kflags & MOUNT_KATTR_IDMAP_REPLACE) && is_idmapped_mnt(m)) + return -EPERM; + + /* The underlying filesystem doesn't support idmapped mounts yet. */ + if (!(m->mnt_sb->s_type->fs_flags & FS_ALLOW_IDMAP)) + return -EINVAL; + + /* The filesystem has turned off idmapped mounts. */ + if (m->mnt_sb->s_iflags & SB_I_NOIDMAP) + return -EINVAL; + + /* We're not controlling the superblock. */ + if (!ns_capable(fs_userns, CAP_SYS_ADMIN)) + return -EPERM; + + /* Mount has already been visible in the filesystem hierarchy. */ + if (!is_anon_ns(mnt->mnt_ns)) + return -EINVAL; + + return 0; +} + +/** + * mnt_allow_writers() - check whether the attribute change allows writers + * @kattr: the new mount attributes + * @mnt: the mount to which @kattr will be applied + * + * Check whether thew new mount attributes in @kattr allow concurrent writers. + * + * Return: true if writers need to be held, false if not + */ +static inline bool mnt_allow_writers(const struct mount_kattr *kattr, + const struct mount *mnt) +{ + return (!(kattr->attr_set & MNT_READONLY) || + (mnt->mnt.mnt_flags & MNT_READONLY)) && + !kattr->mnt_idmap; +} + +static int mount_setattr_prepare(struct mount_kattr *kattr, struct mount *mnt) +{ + struct mount *m; + int err; + + for (m = mnt; m; m = next_mnt(m, mnt)) { + if (!can_change_locked_flags(m, recalc_flags(kattr, m))) { + err = -EPERM; + break; + } + + err = can_idmap_mount(kattr, m); + if (err) + break; + + if (!mnt_allow_writers(kattr, m)) { + err = mnt_hold_writers(m); + if (err) { + m = next_mnt(m, mnt); + break; + } + } + + if (!(kattr->kflags & MOUNT_KATTR_RECURSE)) + return 0; + } + + if (err) { + /* undo all mnt_hold_writers() we'd done */ + for (struct mount *p = mnt; p != m; p = next_mnt(p, mnt)) + mnt_unhold_writers(p); + } + return err; +} + +static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) +{ + struct mnt_idmap *old_idmap; + + if (!kattr->mnt_idmap) + return; + + old_idmap = mnt_idmap(&mnt->mnt); + + /* Pairs with smp_load_acquire() in mnt_idmap(). */ + smp_store_release(&mnt->mnt.mnt_idmap, mnt_idmap_get(kattr->mnt_idmap)); + mnt_idmap_put(old_idmap); +} + +static void mount_setattr_commit(struct mount_kattr *kattr, struct mount *mnt) +{ + struct mount *m; + + for (m = mnt; m; m = next_mnt(m, mnt)) { + unsigned int flags; + + do_idmap_mount(kattr, m); + flags = recalc_flags(kattr, m); + WRITE_ONCE(m->mnt.mnt_flags, flags); + + /* If we had to hold writers unblock them. */ + mnt_unhold_writers(m); + + if (kattr->propagation) + change_mnt_propagation(m, kattr->propagation); + if (!(kattr->kflags & MOUNT_KATTR_RECURSE)) + break; + } + touch_mnt_namespace(mnt->mnt_ns); +} + +static int do_mount_setattr(const struct path *path, struct mount_kattr *kattr) +{ + struct mount *mnt = real_mount(path->mnt); + int err = 0; + + if (!path_mounted(path)) + return -EINVAL; + + if (kattr->mnt_userns) { + struct mnt_idmap *mnt_idmap; + + mnt_idmap = alloc_mnt_idmap(kattr->mnt_userns); + if (IS_ERR(mnt_idmap)) + return PTR_ERR(mnt_idmap); + kattr->mnt_idmap = mnt_idmap; + } + + if (kattr->propagation) { + /* + * Only take namespace_lock() if we're actually changing + * propagation. + */ + namespace_lock(); + if (kattr->propagation == MS_SHARED) { + err = invent_group_ids(mnt, kattr->kflags & MOUNT_KATTR_RECURSE); + if (err) { + namespace_unlock(); + return err; + } + } + } + + err = -EINVAL; + lock_mount_hash(); + + if (!anon_ns_root(mnt) && !check_mnt(mnt)) + goto out; + + /* + * First, we get the mount tree in a shape where we can change mount + * properties without failure. If we succeeded to do so we commit all + * changes and if we failed we clean up. + */ + err = mount_setattr_prepare(kattr, mnt); + if (!err) + mount_setattr_commit(kattr, mnt); + +out: + unlock_mount_hash(); + + if (kattr->propagation) { + if (err) + cleanup_group_ids(mnt, NULL); + namespace_unlock(); + } + + return err; +} + +static int build_mount_idmapped(const struct mount_attr *attr, size_t usize, + struct mount_kattr *kattr) +{ + struct ns_common *ns; + struct user_namespace *mnt_userns; + + if (!((attr->attr_set | attr->attr_clr) & MOUNT_ATTR_IDMAP)) + return 0; + + if (attr->attr_clr & MOUNT_ATTR_IDMAP) { + /* + * We can only remove an idmapping if it's never been + * exposed to userspace. + */ + if (!(kattr->kflags & MOUNT_KATTR_IDMAP_REPLACE)) + return -EINVAL; + + /* + * Removal of idmappings is equivalent to setting + * nop_mnt_idmap. + */ + if (!(attr->attr_set & MOUNT_ATTR_IDMAP)) { + kattr->mnt_idmap = &nop_mnt_idmap; + return 0; + } + } + + if (attr->userns_fd > INT_MAX) + return -EINVAL; + + CLASS(fd, f)(attr->userns_fd); + if (fd_empty(f)) + return -EBADF; + + if (!proc_ns_file(fd_file(f))) + return -EINVAL; + + ns = get_proc_ns(file_inode(fd_file(f))); + if (ns->ns_type != CLONE_NEWUSER) + return -EINVAL; + + /* + * The initial idmapping cannot be used to create an idmapped + * mount. We use the initial idmapping as an indicator of a mount + * that is not idmapped. It can simply be passed into helpers that + * are aware of idmapped mounts as a convenient shortcut. A user + * can just create a dedicated identity mapping to achieve the same + * result. + */ + mnt_userns = container_of(ns, struct user_namespace, ns); + if (mnt_userns == &init_user_ns) + return -EPERM; + + /* We're not controlling the target namespace. */ + if (!ns_capable(mnt_userns, CAP_SYS_ADMIN)) + return -EPERM; + + kattr->mnt_userns = get_user_ns(mnt_userns); + return 0; +} + +static int build_mount_kattr(const struct mount_attr *attr, size_t usize, + struct mount_kattr *kattr) +{ + if (attr->propagation & ~MOUNT_SETATTR_PROPAGATION_FLAGS) + return -EINVAL; + if (hweight32(attr->propagation & MOUNT_SETATTR_PROPAGATION_FLAGS) > 1) + return -EINVAL; + kattr->propagation = attr->propagation; + + if ((attr->attr_set | attr->attr_clr) & ~MOUNT_SETATTR_VALID_FLAGS) + return -EINVAL; + + kattr->attr_set = attr_flags_to_mnt_flags(attr->attr_set); + kattr->attr_clr = attr_flags_to_mnt_flags(attr->attr_clr); + + /* + * Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap, + * users wanting to transition to a different atime setting cannot + * simply specify the atime setting in @attr_set, but must also + * specify MOUNT_ATTR__ATIME in the @attr_clr field. + * So ensure that MOUNT_ATTR__ATIME can't be partially set in + * @attr_clr and that @attr_set can't have any atime bits set if + * MOUNT_ATTR__ATIME isn't set in @attr_clr. + */ + if (attr->attr_clr & MOUNT_ATTR__ATIME) { + if ((attr->attr_clr & MOUNT_ATTR__ATIME) != MOUNT_ATTR__ATIME) + return -EINVAL; + + /* + * Clear all previous time settings as they are mutually + * exclusive. + */ + kattr->attr_clr |= MNT_RELATIME | MNT_NOATIME; + switch (attr->attr_set & MOUNT_ATTR__ATIME) { + case MOUNT_ATTR_RELATIME: + kattr->attr_set |= MNT_RELATIME; + break; + case MOUNT_ATTR_NOATIME: + kattr->attr_set |= MNT_NOATIME; + break; + case MOUNT_ATTR_STRICTATIME: + break; + default: + return -EINVAL; + } + } else { + if (attr->attr_set & MOUNT_ATTR__ATIME) + return -EINVAL; + } + + return build_mount_idmapped(attr, usize, kattr); +} + +static void finish_mount_kattr(struct mount_kattr *kattr) +{ + if (kattr->mnt_userns) { + put_user_ns(kattr->mnt_userns); + kattr->mnt_userns = NULL; + } + + if (kattr->mnt_idmap) + mnt_idmap_put(kattr->mnt_idmap); +} + +static int wants_mount_setattr(struct mount_attr __user *uattr, size_t usize, + struct mount_kattr *kattr) +{ + int ret; + struct mount_attr attr; + + BUILD_BUG_ON(sizeof(struct mount_attr) != MOUNT_ATTR_SIZE_VER0); + + if (unlikely(usize > PAGE_SIZE)) + return -E2BIG; + if (unlikely(usize < MOUNT_ATTR_SIZE_VER0)) + return -EINVAL; + + if (!may_mount()) + return -EPERM; + + ret = copy_struct_from_user(&attr, sizeof(attr), uattr, usize); + if (ret) + return ret; + + /* Don't bother walking through the mounts if this is a nop. */ + if (attr.attr_set == 0 && + attr.attr_clr == 0 && + attr.propagation == 0) + return 0; /* Tell caller to not bother. */ + + ret = build_mount_kattr(&attr, usize, kattr); + if (ret < 0) + return ret; + + return 1; +} + +SYSCALL_DEFINE5(mount_setattr, int, dfd, const char __user *, path, + unsigned int, flags, struct mount_attr __user *, uattr, + size_t, usize) +{ + int err; + struct path target; + struct mount_kattr kattr; + unsigned int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW; + + if (flags & ~(AT_EMPTY_PATH | + AT_RECURSIVE | + AT_SYMLINK_NOFOLLOW | + AT_NO_AUTOMOUNT)) + return -EINVAL; + + if (flags & AT_NO_AUTOMOUNT) + lookup_flags &= ~LOOKUP_AUTOMOUNT; + if (flags & AT_SYMLINK_NOFOLLOW) + lookup_flags &= ~LOOKUP_FOLLOW; + + kattr = (struct mount_kattr) { + .lookup_flags = lookup_flags, + }; + + if (flags & AT_RECURSIVE) + kattr.kflags |= MOUNT_KATTR_RECURSE; + + err = wants_mount_setattr(uattr, usize, &kattr); + if (err <= 0) + return err; + + CLASS(filename_uflags, name)(path, flags); + err = filename_lookup(dfd, name, kattr.lookup_flags, &target, NULL); + if (!err) { + err = do_mount_setattr(&target, &kattr); + path_put(&target); + } + finish_mount_kattr(&kattr); + return err; +} + +SYSCALL_DEFINE5(open_tree_attr, int, dfd, const char __user *, filename, + unsigned, flags, struct mount_attr __user *, uattr, + size_t, usize) +{ + if (!uattr && usize) + return -EINVAL; + + FD_PREPARE(fdf, flags, vfs_open_tree(dfd, filename, flags)); + if (fdf.err) + return fdf.err; + + if (uattr) { + struct mount_kattr kattr = {}; + struct file *file = fd_prepare_file(fdf); + int ret; + + if (flags & OPEN_TREE_CLONE) + kattr.kflags = MOUNT_KATTR_IDMAP_REPLACE; + if (flags & AT_RECURSIVE) + kattr.kflags |= MOUNT_KATTR_RECURSE; + + ret = wants_mount_setattr(uattr, usize, &kattr); + if (ret > 0) { + ret = do_mount_setattr(&file->f_path, &kattr); + finish_mount_kattr(&kattr); + } + if (ret) + return ret; + } + + return fd_publish(fdf); +} + +int show_path(struct seq_file *m, struct dentry *root) +{ + if (root->d_sb->s_op->show_path) + return root->d_sb->s_op->show_path(m, root); + + seq_dentry(m, root, " \t\n\\"); + return 0; +} + +static struct vfsmount *lookup_mnt_in_ns(u64 id, struct mnt_namespace *ns) +{ + struct mount *mnt = mnt_find_id_at(ns, id); + + if (!mnt || mnt->mnt_id_unique != id) + return NULL; + + return &mnt->mnt; +} + +struct kstatmount { + struct statmount __user *buf; + size_t bufsize; + struct vfsmount *mnt; + struct mnt_idmap *idmap; + u64 mask; + struct path root; + struct seq_file seq; + + /* Must be last --ends in a flexible-array member. */ + struct statmount sm; +}; + +static u64 mnt_to_attr_flags(struct vfsmount *mnt) +{ + unsigned int mnt_flags = READ_ONCE(mnt->mnt_flags); + u64 attr_flags = 0; + + if (mnt_flags & MNT_READONLY) + attr_flags |= MOUNT_ATTR_RDONLY; + if (mnt_flags & MNT_NOSUID) + attr_flags |= MOUNT_ATTR_NOSUID; + if (mnt_flags & MNT_NODEV) + attr_flags |= MOUNT_ATTR_NODEV; + if (mnt_flags & MNT_NOEXEC) + attr_flags |= MOUNT_ATTR_NOEXEC; + if (mnt_flags & MNT_NODIRATIME) + attr_flags |= MOUNT_ATTR_NODIRATIME; + if (mnt_flags & MNT_NOSYMFOLLOW) + attr_flags |= MOUNT_ATTR_NOSYMFOLLOW; + + if (mnt_flags & MNT_NOATIME) + attr_flags |= MOUNT_ATTR_NOATIME; + else if (mnt_flags & MNT_RELATIME) + attr_flags |= MOUNT_ATTR_RELATIME; + else + attr_flags |= MOUNT_ATTR_STRICTATIME; + + if (is_idmapped_mnt(mnt)) + attr_flags |= MOUNT_ATTR_IDMAP; + + return attr_flags; +} + +static u64 mnt_to_propagation_flags(struct mount *m) +{ + u64 propagation = 0; + + if (IS_MNT_SHARED(m)) + propagation |= MS_SHARED; + if (IS_MNT_SLAVE(m)) + propagation |= MS_SLAVE; + if (IS_MNT_UNBINDABLE(m)) + propagation |= MS_UNBINDABLE; + if (!propagation) + propagation |= MS_PRIVATE; + + return propagation; +} + +u64 vfsmount_to_propagation_flags(struct vfsmount *mnt) +{ + return mnt_to_propagation_flags(real_mount(mnt)); +} +EXPORT_SYMBOL_GPL(vfsmount_to_propagation_flags); + +static void statmount_sb_basic(struct kstatmount *s) +{ + struct super_block *sb = s->mnt->mnt_sb; + + s->sm.mask |= STATMOUNT_SB_BASIC; + s->sm.sb_dev_major = MAJOR(sb->s_dev); + s->sm.sb_dev_minor = MINOR(sb->s_dev); + s->sm.sb_magic = sb->s_magic; + s->sm.sb_flags = sb->s_flags & (SB_RDONLY|SB_SYNCHRONOUS|SB_DIRSYNC|SB_LAZYTIME); +} + +static void statmount_mnt_basic(struct kstatmount *s) +{ + struct mount *m = real_mount(s->mnt); + + s->sm.mask |= STATMOUNT_MNT_BASIC; + s->sm.mnt_id = m->mnt_id_unique; + s->sm.mnt_parent_id = m->mnt_parent->mnt_id_unique; + s->sm.mnt_id_old = m->mnt_id; + s->sm.mnt_parent_id_old = m->mnt_parent->mnt_id; + s->sm.mnt_attr = mnt_to_attr_flags(&m->mnt); + s->sm.mnt_propagation = mnt_to_propagation_flags(m); + s->sm.mnt_peer_group = m->mnt_group_id; + s->sm.mnt_master = IS_MNT_SLAVE(m) ? m->mnt_master->mnt_group_id : 0; +} + +static void statmount_propagate_from(struct kstatmount *s) +{ + struct mount *m = real_mount(s->mnt); + + s->sm.mask |= STATMOUNT_PROPAGATE_FROM; + if (IS_MNT_SLAVE(m)) + s->sm.propagate_from = get_dominating_id(m, ¤t->fs->root); +} + +static int statmount_mnt_root(struct kstatmount *s, struct seq_file *seq) +{ + int ret; + size_t start = seq->count; + + ret = show_path(seq, s->mnt->mnt_root); + if (ret) + return ret; + + if (unlikely(seq_has_overflowed(seq))) + return -EAGAIN; + + /* + * Unescape the result. It would be better if supplied string was not + * escaped in the first place, but that's a pretty invasive change. + */ + seq->buf[seq->count] = '\0'; + seq->count = start; + seq_commit(seq, string_unescape_inplace(seq->buf + start, UNESCAPE_OCTAL)); + return 0; +} + +static int statmount_mnt_point(struct kstatmount *s, struct seq_file *seq) +{ + struct vfsmount *mnt = s->mnt; + struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; + int err; + + err = seq_path_root(seq, &mnt_path, &s->root, ""); + return err == SEQ_SKIP ? 0 : err; +} + +static int statmount_fs_type(struct kstatmount *s, struct seq_file *seq) +{ + struct super_block *sb = s->mnt->mnt_sb; + + seq_puts(seq, sb->s_type->name); + return 0; +} + +static void statmount_fs_subtype(struct kstatmount *s, struct seq_file *seq) +{ + struct super_block *sb = s->mnt->mnt_sb; + + if (sb->s_subtype) + seq_puts(seq, sb->s_subtype); +} + +static int statmount_sb_source(struct kstatmount *s, struct seq_file *seq) +{ + struct super_block *sb = s->mnt->mnt_sb; + struct mount *r = real_mount(s->mnt); + + if (sb->s_op->show_devname) { + size_t start = seq->count; + int ret; + + ret = sb->s_op->show_devname(seq, s->mnt->mnt_root); + if (ret) + return ret; + + if (unlikely(seq_has_overflowed(seq))) + return -EAGAIN; + + /* Unescape the result */ + seq->buf[seq->count] = '\0'; + seq->count = start; + seq_commit(seq, string_unescape_inplace(seq->buf + start, UNESCAPE_OCTAL)); + } else { + seq_puts(seq, r->mnt_devname); + } + return 0; +} + +static void statmount_mnt_ns_id(struct kstatmount *s, struct mnt_namespace *ns) +{ + s->sm.mask |= STATMOUNT_MNT_NS_ID; + s->sm.mnt_ns_id = ns->ns.ns_id; +} + +static int statmount_mnt_opts(struct kstatmount *s, struct seq_file *seq) +{ + struct vfsmount *mnt = s->mnt; + struct super_block *sb = mnt->mnt_sb; + size_t start = seq->count; + int err; + + err = security_sb_show_options(seq, sb); + if (err) + return err; + + if (sb->s_op->show_options) { + err = sb->s_op->show_options(seq, mnt->mnt_root); + if (err) + return err; + } + + if (unlikely(seq_has_overflowed(seq))) + return -EAGAIN; + + if (seq->count == start) + return 0; + + /* skip leading comma */ + memmove(seq->buf + start, seq->buf + start + 1, + seq->count - start - 1); + seq->count--; + + return 0; +} + +static inline int statmount_opt_process(struct seq_file *seq, size_t start) +{ + char *buf_end, *opt_end, *src, *dst; + int count = 0; + + if (unlikely(seq_has_overflowed(seq))) + return -EAGAIN; + + buf_end = seq->buf + seq->count; + dst = seq->buf + start; + src = dst + 1; /* skip initial comma */ + + if (src >= buf_end) { + seq->count = start; + return 0; + } + + *buf_end = '\0'; + for (; src < buf_end; src = opt_end + 1) { + opt_end = strchrnul(src, ','); + *opt_end = '\0'; + dst += string_unescape(src, dst, 0, UNESCAPE_OCTAL) + 1; + if (WARN_ON_ONCE(++count == INT_MAX)) + return -EOVERFLOW; + } + seq->count = dst - 1 - seq->buf; + return count; +} + +static int statmount_opt_array(struct kstatmount *s, struct seq_file *seq) +{ + struct vfsmount *mnt = s->mnt; + struct super_block *sb = mnt->mnt_sb; + size_t start = seq->count; + int err; + + if (!sb->s_op->show_options) + return 0; + + err = sb->s_op->show_options(seq, mnt->mnt_root); + if (err) + return err; + + err = statmount_opt_process(seq, start); + if (err < 0) + return err; + + s->sm.opt_num = err; + return 0; +} + +static int statmount_opt_sec_array(struct kstatmount *s, struct seq_file *seq) +{ + struct vfsmount *mnt = s->mnt; + struct super_block *sb = mnt->mnt_sb; + size_t start = seq->count; + int err; + + err = security_sb_show_options(seq, sb); + if (err) + return err; + + err = statmount_opt_process(seq, start); + if (err < 0) + return err; + + s->sm.opt_sec_num = err; + return 0; +} + +static inline int statmount_mnt_uidmap(struct kstatmount *s, struct seq_file *seq) +{ + int ret; + + ret = statmount_mnt_idmap(s->idmap, seq, true); + if (ret < 0) + return ret; + + s->sm.mnt_uidmap_num = ret; + /* + * Always raise STATMOUNT_MNT_UIDMAP even if there are no valid + * mappings. This allows userspace to distinguish between a + * non-idmapped mount and an idmapped mount where none of the + * individual mappings are valid in the caller's idmapping. + */ + if (is_valid_mnt_idmap(s->idmap)) + s->sm.mask |= STATMOUNT_MNT_UIDMAP; + return 0; +} + +static inline int statmount_mnt_gidmap(struct kstatmount *s, struct seq_file *seq) +{ + int ret; + + ret = statmount_mnt_idmap(s->idmap, seq, false); + if (ret < 0) + return ret; + + s->sm.mnt_gidmap_num = ret; + /* + * Always raise STATMOUNT_MNT_GIDMAP even if there are no valid + * mappings. This allows userspace to distinguish between a + * non-idmapped mount and an idmapped mount where none of the + * individual mappings are valid in the caller's idmapping. + */ + if (is_valid_mnt_idmap(s->idmap)) + s->sm.mask |= STATMOUNT_MNT_GIDMAP; + return 0; +} + +static int statmount_string(struct kstatmount *s, u64 flag) +{ + int ret = 0; + size_t kbufsize; + struct seq_file *seq = &s->seq; + struct statmount *sm = &s->sm; + u32 start, *offp; + + /* Reserve an empty string at the beginning for any unset offsets */ + if (!seq->count) + seq_putc(seq, 0); + + start = seq->count; + + switch (flag) { + case STATMOUNT_FS_TYPE: + offp = &sm->fs_type; + ret = statmount_fs_type(s, seq); + break; + case STATMOUNT_MNT_ROOT: + offp = &sm->mnt_root; + ret = statmount_mnt_root(s, seq); + break; + case STATMOUNT_MNT_POINT: + offp = &sm->mnt_point; + ret = statmount_mnt_point(s, seq); + break; + case STATMOUNT_MNT_OPTS: + offp = &sm->mnt_opts; + ret = statmount_mnt_opts(s, seq); + break; + case STATMOUNT_OPT_ARRAY: + offp = &sm->opt_array; + ret = statmount_opt_array(s, seq); + break; + case STATMOUNT_OPT_SEC_ARRAY: + offp = &sm->opt_sec_array; + ret = statmount_opt_sec_array(s, seq); + break; + case STATMOUNT_FS_SUBTYPE: + offp = &sm->fs_subtype; + statmount_fs_subtype(s, seq); + break; + case STATMOUNT_SB_SOURCE: + offp = &sm->sb_source; + ret = statmount_sb_source(s, seq); + break; + case STATMOUNT_MNT_UIDMAP: + offp = &sm->mnt_uidmap; + ret = statmount_mnt_uidmap(s, seq); + break; + case STATMOUNT_MNT_GIDMAP: + offp = &sm->mnt_gidmap; + ret = statmount_mnt_gidmap(s, seq); + break; + default: + WARN_ON_ONCE(true); + return -EINVAL; + } + + /* + * If nothing was emitted, return to avoid setting the flag + * and terminating the buffer. + */ + if (seq->count == start) + return ret; + if (unlikely(check_add_overflow(sizeof(*sm), seq->count, &kbufsize))) + return -EOVERFLOW; + if (kbufsize >= s->bufsize) + return -EOVERFLOW; + + /* signal a retry */ + if (unlikely(seq_has_overflowed(seq))) + return -EAGAIN; + + if (ret) + return ret; + + seq->buf[seq->count++] = '\0'; + sm->mask |= flag; + *offp = start; + return 0; +} + +static int copy_statmount_to_user(struct kstatmount *s) +{ + struct statmount *sm = &s->sm; + struct seq_file *seq = &s->seq; + char __user *str = ((char __user *)s->buf) + sizeof(*sm); + size_t copysize = min_t(size_t, s->bufsize, sizeof(*sm)); + + if (seq->count && copy_to_user(str, seq->buf, seq->count)) + return -EFAULT; + + /* Return the number of bytes copied to the buffer */ + sm->size = copysize + seq->count; + if (copy_to_user(s->buf, sm, copysize)) + return -EFAULT; + + return 0; +} + +static struct mount *listmnt_next(struct mount *curr, bool reverse) +{ + struct rb_node *node; + + if (reverse) + node = rb_prev(&curr->mnt_node); + else + node = rb_next(&curr->mnt_node); + + return node_to_mount(node); +} + +static int grab_requested_root(struct mnt_namespace *ns, struct path *root) +{ + struct mount *first, *child; + + rwsem_assert_held(&namespace_sem); + + /* We're looking at our own ns, just use get_fs_root. */ + if (ns == current->nsproxy->mnt_ns) { + get_fs_root(current->fs, root); + return 0; + } + + /* + * We have to find the first mount in our ns and use that, however it + * may not exist, so handle that properly. + */ + if (mnt_ns_empty(ns)) + return -ENOENT; + + first = ns->root; + for (child = node_to_mount(ns->mnt_first_node); child; + child = listmnt_next(child, false)) { + if (child != first && child->mnt_parent == first) + break; + } + if (!child) + return -ENOENT; + + root->mnt = mntget(&child->mnt); + root->dentry = dget(root->mnt->mnt_root); + return 0; +} + +/* This must be updated whenever a new flag is added */ +#define STATMOUNT_SUPPORTED (STATMOUNT_SB_BASIC | \ + STATMOUNT_MNT_BASIC | \ + STATMOUNT_PROPAGATE_FROM | \ + STATMOUNT_MNT_ROOT | \ + STATMOUNT_MNT_POINT | \ + STATMOUNT_FS_TYPE | \ + STATMOUNT_MNT_NS_ID | \ + STATMOUNT_MNT_OPTS | \ + STATMOUNT_FS_SUBTYPE | \ + STATMOUNT_SB_SOURCE | \ + STATMOUNT_OPT_ARRAY | \ + STATMOUNT_OPT_SEC_ARRAY | \ + STATMOUNT_SUPPORTED_MASK | \ + STATMOUNT_MNT_UIDMAP | \ + STATMOUNT_MNT_GIDMAP) + +/* locks: namespace_shared */ +static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id, + struct file *mnt_file, struct mnt_namespace *ns) +{ + int err; + + if (mnt_file) { + WARN_ON_ONCE(ns != NULL); + + s->mnt = mnt_file->f_path.mnt; + ns = real_mount(s->mnt)->mnt_ns; + if (IS_ERR(ns)) + return PTR_ERR(ns); + if (!ns) + /* + * We can't set mount point and mnt_ns_id since we don't have a + * ns for the mount. This can happen if the mount is unmounted + * with MNT_DETACH. + */ + s->mask &= ~(STATMOUNT_MNT_POINT | STATMOUNT_MNT_NS_ID); + } else { + /* Has the namespace already been emptied? */ + if (mnt_ns_id && mnt_ns_empty(ns)) + return -ENOENT; + + s->mnt = lookup_mnt_in_ns(mnt_id, ns); + if (!s->mnt) + return -ENOENT; + } + + if (ns) { + err = grab_requested_root(ns, &s->root); + if (err) + return err; + + if (!mnt_file) { + struct mount *m; + /* + * Don't trigger audit denials. We just want to determine what + * mounts to show users. + */ + m = real_mount(s->mnt); + if (!is_path_reachable(m, m->mnt.mnt_root, &s->root) && + !ns_capable_noaudit(ns->user_ns, CAP_SYS_ADMIN)) + return -EPERM; + } + } + + err = security_sb_statfs(s->mnt->mnt_root); + if (err) + return err; + + /* + * Note that mount properties in mnt->mnt_flags, mnt->mnt_idmap + * can change concurrently as we only hold the read-side of the + * namespace semaphore and mount properties may change with only + * the mount lock held. + * + * We could sample the mount lock sequence counter to detect + * those changes and retry. But it's not worth it. Worst that + * happens is that the mnt->mnt_idmap pointer is already changed + * while mnt->mnt_flags isn't or vica versa. So what. + * + * Both mnt->mnt_flags and mnt->mnt_idmap are set and retrieved + * via READ_ONCE()/WRITE_ONCE() and guard against theoretical + * torn read/write. That's all we care about right now. + */ + s->idmap = mnt_idmap(s->mnt); + if (s->mask & STATMOUNT_MNT_BASIC) + statmount_mnt_basic(s); + + if (s->mask & STATMOUNT_SB_BASIC) + statmount_sb_basic(s); + + if (s->mask & STATMOUNT_PROPAGATE_FROM) + statmount_propagate_from(s); + + if (s->mask & STATMOUNT_FS_TYPE) + err = statmount_string(s, STATMOUNT_FS_TYPE); + + if (!err && s->mask & STATMOUNT_MNT_ROOT) + err = statmount_string(s, STATMOUNT_MNT_ROOT); + + if (!err && s->mask & STATMOUNT_MNT_POINT) + err = statmount_string(s, STATMOUNT_MNT_POINT); + + if (!err && s->mask & STATMOUNT_MNT_OPTS) + err = statmount_string(s, STATMOUNT_MNT_OPTS); + + if (!err && s->mask & STATMOUNT_OPT_ARRAY) + err = statmount_string(s, STATMOUNT_OPT_ARRAY); + + if (!err && s->mask & STATMOUNT_OPT_SEC_ARRAY) + err = statmount_string(s, STATMOUNT_OPT_SEC_ARRAY); + + if (!err && s->mask & STATMOUNT_FS_SUBTYPE) + err = statmount_string(s, STATMOUNT_FS_SUBTYPE); + + if (!err && s->mask & STATMOUNT_SB_SOURCE) + err = statmount_string(s, STATMOUNT_SB_SOURCE); + + if (!err && s->mask & STATMOUNT_MNT_UIDMAP) + err = statmount_string(s, STATMOUNT_MNT_UIDMAP); + + if (!err && s->mask & STATMOUNT_MNT_GIDMAP) + err = statmount_string(s, STATMOUNT_MNT_GIDMAP); + + if (!err && s->mask & STATMOUNT_MNT_NS_ID) + statmount_mnt_ns_id(s, ns); + + if (!err && s->mask & STATMOUNT_SUPPORTED_MASK) { + s->sm.mask |= STATMOUNT_SUPPORTED_MASK; + s->sm.supported_mask = STATMOUNT_SUPPORTED; + } + + if (err) + return err; + + /* Are there bits in the return mask not present in STATMOUNT_SUPPORTED? */ + WARN_ON_ONCE(~STATMOUNT_SUPPORTED & s->sm.mask); + + return 0; +} + +static inline bool retry_statmount(const long ret, size_t *seq_size) +{ + if (likely(ret != -EAGAIN)) + return false; + if (unlikely(check_mul_overflow(*seq_size, 2, seq_size))) + return false; + if (unlikely(*seq_size > MAX_RW_COUNT)) + return false; + return true; +} + +#define STATMOUNT_STRING_REQ (STATMOUNT_MNT_ROOT | STATMOUNT_MNT_POINT | \ + STATMOUNT_FS_TYPE | STATMOUNT_MNT_OPTS | \ + STATMOUNT_FS_SUBTYPE | STATMOUNT_SB_SOURCE | \ + STATMOUNT_OPT_ARRAY | STATMOUNT_OPT_SEC_ARRAY | \ + STATMOUNT_MNT_UIDMAP | STATMOUNT_MNT_GIDMAP) + +static int prepare_kstatmount(struct kstatmount *ks, struct mnt_id_req *kreq, + struct statmount __user *buf, size_t bufsize, + size_t seq_size) +{ + if (!access_ok(buf, bufsize)) + return -EFAULT; + + memset(ks, 0, sizeof(*ks)); + ks->mask = kreq->param; + ks->buf = buf; + ks->bufsize = bufsize; + + if (ks->mask & STATMOUNT_STRING_REQ) { + if (bufsize == sizeof(ks->sm)) + return -EOVERFLOW; + + ks->seq.buf = kvmalloc(seq_size, GFP_KERNEL_ACCOUNT); + if (!ks->seq.buf) + return -ENOMEM; + + ks->seq.size = seq_size; + } + + return 0; +} + +static int copy_mnt_id_req(const struct mnt_id_req __user *req, + struct mnt_id_req *kreq, unsigned int flags) +{ + int ret; + size_t usize; + + BUILD_BUG_ON(sizeof(struct mnt_id_req) != MNT_ID_REQ_SIZE_VER1); + + ret = get_user(usize, &req->size); + if (ret) + return -EFAULT; + if (unlikely(usize > PAGE_SIZE)) + return -E2BIG; + if (unlikely(usize < MNT_ID_REQ_SIZE_VER0)) + return -EINVAL; + memset(kreq, 0, sizeof(*kreq)); + ret = copy_struct_from_user(kreq, sizeof(*kreq), req, usize); + if (ret) + return ret; + + if (flags & STATMOUNT_BY_FD) { + if (kreq->mnt_id || kreq->mnt_ns_id) + return -EINVAL; + } else { + if (kreq->mnt_ns_fd != 0 && kreq->mnt_ns_id) + return -EINVAL; + /* The first valid unique mount id is MNT_UNIQUE_ID_OFFSET + 1. */ + if (kreq->mnt_id <= MNT_UNIQUE_ID_OFFSET) + return -EINVAL; + } + return 0; +} + +/* + * If the user requested a specific mount namespace id, look that up and return + * that, or if not simply grab a passive reference on our mount namespace and + * return that. + */ +static struct mnt_namespace *grab_requested_mnt_ns(const struct mnt_id_req *kreq) +{ + struct mnt_namespace *mnt_ns; + + if (kreq->mnt_ns_id) { + mnt_ns = lookup_mnt_ns(kreq->mnt_ns_id); + if (!mnt_ns) + return ERR_PTR(-ENOENT); + } else if (kreq->mnt_ns_fd) { + struct ns_common *ns; + + CLASS(fd, f)(kreq->mnt_ns_fd); + if (fd_empty(f)) + return ERR_PTR(-EBADF); + + if (!proc_ns_file(fd_file(f))) + return ERR_PTR(-EINVAL); + + ns = get_proc_ns(file_inode(fd_file(f))); + if (ns->ns_type != CLONE_NEWNS) + return ERR_PTR(-EINVAL); + + mnt_ns = to_mnt_ns(ns); + refcount_inc(&mnt_ns->passive); + } else { + mnt_ns = current->nsproxy->mnt_ns; + refcount_inc(&mnt_ns->passive); + } + + return mnt_ns; +} + +SYSCALL_DEFINE4(statmount, const struct mnt_id_req __user *, req, + struct statmount __user *, buf, size_t, bufsize, + unsigned int, flags) +{ + struct mnt_namespace *ns __free(mnt_ns_release) = NULL; + struct kstatmount *ks __free(kfree) = NULL; + struct file *mnt_file __free(fput) = NULL; + struct mnt_id_req kreq; + /* We currently support retrieval of 3 strings. */ + size_t seq_size = 3 * PATH_MAX; + int ret; + + if (flags & ~STATMOUNT_BY_FD) + return -EINVAL; + + ret = copy_mnt_id_req(req, &kreq, flags); + if (ret) + return ret; + + if (flags & STATMOUNT_BY_FD) { + mnt_file = fget_raw(kreq.mnt_fd); + if (!mnt_file) + return -EBADF; + /* do_statmount sets ns in case of STATMOUNT_BY_FD */ + } else { + ns = grab_requested_mnt_ns(&kreq); + if (IS_ERR(ns)) + return PTR_ERR(ns); + + if (kreq.mnt_ns_id && (ns != current->nsproxy->mnt_ns) && + !ns_capable_noaudit(ns->user_ns, CAP_SYS_ADMIN)) + return -EPERM; + } + + ks = kmalloc(sizeof(*ks), GFP_KERNEL_ACCOUNT); + if (!ks) + return -ENOMEM; + +retry: + ret = prepare_kstatmount(ks, &kreq, buf, bufsize, seq_size); + if (ret) + return ret; + + scoped_guard(namespace_shared) + ret = do_statmount(ks, kreq.mnt_id, kreq.mnt_ns_id, mnt_file, ns); + + if (!ret) + ret = copy_statmount_to_user(ks); + kvfree(ks->seq.buf); + path_put(&ks->root); + if (retry_statmount(ret, &seq_size)) + goto retry; + return ret; +} + +struct klistmount { + u64 last_mnt_id; + u64 mnt_parent_id; + u64 *kmnt_ids; + u32 nr_mnt_ids; + struct mnt_namespace *ns; + struct path root; +}; + +/* locks: namespace_shared */ +static ssize_t do_listmount(struct klistmount *kls, bool reverse) +{ + struct mnt_namespace *ns = kls->ns; + u64 mnt_parent_id = kls->mnt_parent_id; + u64 last_mnt_id = kls->last_mnt_id; + u64 *mnt_ids = kls->kmnt_ids; + size_t nr_mnt_ids = kls->nr_mnt_ids; + struct path orig; + struct mount *r, *first; + ssize_t ret; + + rwsem_assert_held(&namespace_sem); + + ret = grab_requested_root(ns, &kls->root); + if (ret) + return ret; + + if (mnt_parent_id == LSMT_ROOT) { + orig = kls->root; + } else { + orig.mnt = lookup_mnt_in_ns(mnt_parent_id, ns); + if (!orig.mnt) + return -ENOENT; + orig.dentry = orig.mnt->mnt_root; + } + + /* + * Don't trigger audit denials. We just want to determine what + * mounts to show users. + */ + if (!is_path_reachable(real_mount(orig.mnt), orig.dentry, &kls->root) && + !ns_capable_noaudit(ns->user_ns, CAP_SYS_ADMIN)) + return -EPERM; + + ret = security_sb_statfs(orig.dentry); + if (ret) + return ret; + + if (!last_mnt_id) { + if (reverse) + first = node_to_mount(ns->mnt_last_node); + else + first = node_to_mount(ns->mnt_first_node); + } else { + if (reverse) + first = mnt_find_id_at_reverse(ns, last_mnt_id - 1); + else + first = mnt_find_id_at(ns, last_mnt_id + 1); + } + + for (ret = 0, r = first; r && nr_mnt_ids; r = listmnt_next(r, reverse)) { + if (r->mnt_id_unique == mnt_parent_id) + continue; + if (!is_path_reachable(r, r->mnt.mnt_root, &orig)) + continue; + *mnt_ids = r->mnt_id_unique; + mnt_ids++; + nr_mnt_ids--; + ret++; + } + return ret; +} + +static void __free_klistmount_free(const struct klistmount *kls) +{ + path_put(&kls->root); + kvfree(kls->kmnt_ids); + mnt_ns_release(kls->ns); +} + +static inline int prepare_klistmount(struct klistmount *kls, struct mnt_id_req *kreq, + size_t nr_mnt_ids) +{ + u64 last_mnt_id = kreq->param; + struct mnt_namespace *ns; + + /* The first valid unique mount id is MNT_UNIQUE_ID_OFFSET + 1. */ + if (last_mnt_id != 0 && last_mnt_id <= MNT_UNIQUE_ID_OFFSET) + return -EINVAL; + + kls->last_mnt_id = last_mnt_id; + + kls->nr_mnt_ids = nr_mnt_ids; + kls->kmnt_ids = kvmalloc_array(nr_mnt_ids, sizeof(*kls->kmnt_ids), + GFP_KERNEL_ACCOUNT); + if (!kls->kmnt_ids) + return -ENOMEM; + + ns = grab_requested_mnt_ns(kreq); + if (IS_ERR(ns)) + return PTR_ERR(ns); + kls->ns = ns; + + kls->mnt_parent_id = kreq->mnt_id; + return 0; +} + +SYSCALL_DEFINE4(listmount, const struct mnt_id_req __user *, req, + u64 __user *, mnt_ids, size_t, nr_mnt_ids, unsigned int, flags) +{ + struct klistmount kls __free(klistmount_free) = {}; + const size_t maxcount = 1000000; + struct mnt_id_req kreq; + ssize_t ret; + + if (flags & ~LISTMOUNT_REVERSE) + return -EINVAL; + + /* + * If the mount namespace really has more than 1 million mounts the + * caller must iterate over the mount namespace (and reconsider their + * system design...). + */ + if (unlikely(nr_mnt_ids > maxcount)) + return -EOVERFLOW; + + if (!access_ok(mnt_ids, nr_mnt_ids * sizeof(*mnt_ids))) + return -EFAULT; + + ret = copy_mnt_id_req(req, &kreq, 0); + if (ret) + return ret; + + ret = prepare_klistmount(&kls, &kreq, nr_mnt_ids); + if (ret) + return ret; + + if (kreq.mnt_ns_id && (kls.ns != current->nsproxy->mnt_ns) && + !ns_capable_noaudit(kls.ns->user_ns, CAP_SYS_ADMIN)) + return -ENOENT; + + /* + * We only need to guard against mount topology changes as + * listmount() doesn't care about any mount properties. + */ + scoped_guard(namespace_shared) + ret = do_listmount(&kls, (flags & LISTMOUNT_REVERSE)); + if (ret <= 0) + return ret; + + if (copy_to_user(mnt_ids, kls.kmnt_ids, ret * sizeof(*mnt_ids))) + return -EFAULT; + + return ret; +} + +struct mnt_namespace init_mnt_ns = { + .ns = NS_COMMON_INIT(init_mnt_ns), + .user_ns = &init_user_ns, + .passive = REFCOUNT_INIT(1), + .mounts = RB_ROOT, + .poll = __WAIT_QUEUE_HEAD_INITIALIZER(init_mnt_ns.poll), +}; + +static void __init init_mount_tree(void) +{ + struct vfsmount *mnt, *nullfs_mnt; + struct mount *mnt_root; + struct path root; + + /* + * We create three mounts: + * + * (1) nullfs with mount id 1 + * (2) mutable rootfs with mount id 2 + * (3) private nullfs for kthreads (SB_KERNMOUNT) + * + * with (2) mounted on top of (1). The init_task's root and pwd + * are pointed at (3) so all kthreads start isolated in nullfs. + */ + nullfs_mnt = vfs_kern_mount(&nullfs_fs_type, 0, "nullfs", NULL); + if (IS_ERR(nullfs_mnt)) + panic("VFS: Failed to create nullfs"); + + mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", initramfs_options); + if (IS_ERR(mnt)) + panic("Can't create rootfs"); + + VFS_WARN_ON_ONCE(real_mount(nullfs_mnt)->mnt_id != 1); + VFS_WARN_ON_ONCE(real_mount(mnt)->mnt_id != 2); + + /* The namespace root is the nullfs mnt. */ + mnt_root = real_mount(nullfs_mnt); + init_mnt_ns.root = mnt_root; + + /* Mount mutable rootfs on top of nullfs. */ + root.mnt = nullfs_mnt; + root.dentry = nullfs_mnt->mnt_root; + + LOCK_MOUNT_EXACT(mp, &root); + if (unlikely(IS_ERR(mp.parent))) + panic("VFS: Failed to mount rootfs on nullfs"); + scoped_guard(mount_writer) + attach_mnt(real_mount(mnt), mp.parent, mp.mp); + + pr_info("VFS: Finished mounting rootfs on nullfs\n"); + + /* + * We've dropped all locks here but that's fine. Not just are we + * the only task that's running, there's no other mount + * namespace in existence and the initial mount namespace is + * completely empty until we add the mounts we just created. + */ + for (struct mount *p = mnt_root; p; p = next_mnt(p, mnt_root)) { + mnt_add_to_ns(&init_mnt_ns, p); + init_mnt_ns.nr_mounts++; + } + + nullfs_mnt = kern_mount(&nullfs_fs_type); + if (IS_ERR(nullfs_mnt)) + panic("VFS: Failed to create private nullfs instance"); + root.mnt = nullfs_mnt; + root.dentry = nullfs_mnt->mnt_root; + + init_task.nsproxy->mnt_ns = &init_mnt_ns; + get_mnt_ns(&init_mnt_ns); + set_fs_pwd(current->fs, &root); + set_fs_root(current->fs, &root); + + ns_tree_add(&init_mnt_ns); +} + +void __init mnt_init(void) +{ + int err; + + mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), + 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); + + mount_hashtable = alloc_large_system_hash("Mount-cache", + sizeof(struct hlist_head), + mhash_entries, 19, + HASH_ZERO, + &m_hash_shift, &m_hash_mask, 0, 0); + mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache", + sizeof(struct hlist_head), + mphash_entries, 19, + HASH_ZERO, + &mp_hash_shift, &mp_hash_mask, 0, 0); + + super_dev_init(); + + kernfs_init(); + + err = sysfs_init(); + if (err) + printk(KERN_WARNING "%s: sysfs_init error: %d\n", + __func__, err); + fs_kobj = kobject_create_and_add("fs", NULL); + if (!fs_kobj) + printk(KERN_WARNING "%s: kobj create error\n", __func__); + shmem_init(); + init_rootfs(); + init_mount_tree(); + failfs_init(); +} + +void put_mnt_ns(struct mnt_namespace *ns) +{ + if (!ns_ref_put(ns)) + return; + guard(namespace_excl)(); + emptied_ns = ns; + guard(mount_writer)(); + umount_tree(ns->root, UMOUNT_CONNECTED); +} + +struct vfsmount *kern_mount(struct file_system_type *type) +{ + struct vfsmount *mnt; + mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL); + if (!IS_ERR(mnt)) { + /* + * it is a longterm mount, don't release mnt until + * we unmount before file sys is unregistered + */ + real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; + } + return mnt; +} +EXPORT_SYMBOL_GPL(kern_mount); + +void kern_unmount(struct vfsmount *mnt) +{ + /* release long term mount so mount point can be released */ + if (!IS_ERR(mnt)) { + mnt_make_shortterm(mnt); + synchronize_rcu(); /* yecchhh... */ + mntput(mnt); + } +} +EXPORT_SYMBOL(kern_unmount); + +void kern_unmount_array(struct vfsmount *mnt[], unsigned int num) +{ + unsigned int i; + + for (i = 0; i < num; i++) + mnt_make_shortterm(mnt[i]); + synchronize_rcu_expedited(); + for (i = 0; i < num; i++) + mntput(mnt[i]); +} +EXPORT_SYMBOL(kern_unmount_array); + +bool our_mnt(struct vfsmount *mnt) +{ + return check_mnt(real_mount(mnt)); +} + +bool current_chrooted(void) +{ + /* Does the current process have a non-standard root */ + struct path fs_root __free(path_put) = {}; + struct mount *root; + + get_fs_root(current->fs, &fs_root); + + /* Find the namespace root */ + + guard(mount_locked_reader)(); + + root = topmost_overmount(current->nsproxy->mnt_ns->root); + + return fs_root.mnt != &root->mnt || !path_mounted(&fs_root); +} + +static bool mnt_already_visible(struct mnt_namespace *ns, + const struct super_block *sb, + int *new_mnt_flags) +{ + int new_flags = *new_mnt_flags; + struct mount *mnt; + + /* Don't acquire namespace semaphore without a good reason. */ + if (hlist_empty(&ns->mnt_visible_mounts)) + return false; + + guard(namespace_shared)(); + hlist_for_each_entry(mnt, &ns->mnt_visible_mounts, mnt_ns_visible) { + const struct super_block *sb_visible = mnt->mnt.mnt_sb; + struct mount *child; + int mnt_flags; + + if (sb_visible->s_type != sb->s_type) + continue; + + /* + * Restricted variants are not compatible with anything, even + * other restricted variants. + */ + if (sb_visible->s_iflags & SB_I_RESTRICTED_VARIANT) + continue; + + /* A local view of the mount flags */ + mnt_flags = mnt->mnt.mnt_flags; + + /* Don't miss readonly hidden in the superblock flags */ + if (sb_rdonly(mnt->mnt.mnt_sb)) + mnt_flags |= MNT_LOCK_READONLY; + + /* Verify the mount flags are equal to or more permissive + * than the proposed new mount. + */ + if ((mnt_flags & MNT_LOCK_READONLY) && + !(new_flags & MNT_READONLY)) + continue; + if ((mnt_flags & MNT_LOCK_ATIME) && + ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK))) + continue; + + /* This mount is not fully visible if there are any + * locked child mounts that cover anything except for + * empty directories. + */ + list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { + struct inode *inode = child->mnt_mountpoint->d_inode; + /* Only worry about locked mounts */ + if (!(child->mnt.mnt_flags & MNT_LOCKED)) + continue; + /* Is the directory permanently empty? */ + if (!is_empty_dir_inode(inode)) + goto next; + } + /* Preserve the locked attributes */ + *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \ + MNT_LOCK_ATIME); + return true; + next: ; + } + return false; +} + +static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags) +{ + const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV; + struct mnt_namespace *ns = current->nsproxy->mnt_ns; + unsigned long s_iflags; + + if (ns->user_ns == &init_user_ns) + return false; + + /* Can this filesystem be too revealing? */ + if (!(sb->s_type->fs_flags & FS_USERNS_MOUNT_RESTRICTED)) + return false; + + s_iflags = sb->s_iflags; + if ((s_iflags & required_iflags) != required_iflags) { + WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n", + required_iflags); + return true; + } + + /* + * Restricted variants don't need an already visible mount because they + * don't expose the full filesystem view. + */ + if (s_iflags & SB_I_RESTRICTED_VARIANT) + return false; + + return !mnt_already_visible(ns, sb, new_mnt_flags); +} + +bool mnt_may_suid(struct vfsmount *mnt) +{ + /* + * Foreign mounts (accessed via fchdir or through /proc + * symlinks) are always treated as if they are nosuid. This + * prevents namespaces from trusting potentially unsafe + * suid/sgid bits, file caps, or security labels that originate + * in other namespaces. + */ + return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) && + current_in_userns(mnt->mnt_sb->s_user_ns); +} + +static struct ns_common *mntns_get(struct task_struct *task) +{ + struct ns_common *ns = NULL; + struct nsproxy *nsproxy; + + task_lock(task); + nsproxy = task->nsproxy; + if (nsproxy) { + ns = &nsproxy->mnt_ns->ns; + get_mnt_ns(to_mnt_ns(ns)); + } + task_unlock(task); + + return ns; +} + +static void mntns_put(struct ns_common *ns) +{ + put_mnt_ns(to_mnt_ns(ns)); +} + +static int mntns_install(struct nsset *nsset, struct ns_common *ns) +{ + struct nsproxy *nsproxy = nsset->nsproxy; + struct fs_struct *fs = nsset->fs; + struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns; + struct user_namespace *user_ns = nsset->cred->user_ns; + struct path root; + int err; + + if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || + !ns_capable(user_ns, CAP_SYS_CHROOT) || + !ns_capable(user_ns, CAP_SYS_ADMIN)) + return -EPERM; + + if (is_anon_ns(mnt_ns)) + return -EINVAL; + + if (fs->users != 1) + return -EINVAL; + + get_mnt_ns(mnt_ns); + old_mnt_ns = nsproxy->mnt_ns; + nsproxy->mnt_ns = mnt_ns; + + /* Find the root */ + err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt, + "/", LOOKUP_DOWN, &root); + if (err) { + /* revert to old namespace */ + nsproxy->mnt_ns = old_mnt_ns; + put_mnt_ns(mnt_ns); + return err; + } + + put_mnt_ns(old_mnt_ns); + + /* Update the pwd and root */ + set_fs_pwd(fs, &root); + set_fs_root(fs, &root); + + path_put(&root); + return 0; +} + +static struct user_namespace *mntns_owner(struct ns_common *ns) +{ + return to_mnt_ns(ns)->user_ns; +} + +const struct proc_ns_operations mntns_operations = { + .name = "mnt", + .get = mntns_get, + .put = mntns_put, + .install = mntns_install, + .owner = mntns_owner, +}; + +#ifdef CONFIG_SYSCTL +static const struct ctl_table fs_namespace_sysctls[] = { + { + .procname = "mount-max", + .data = &sysctl_mount_max, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ONE, + }, +}; + +static int __init init_fs_namespace_sysctls(void) +{ + register_sysctl_init("fs", fs_namespace_sysctls); + return 0; +} +fs_initcall(init_fs_namespace_sysctls); + +#endif /* CONFIG_SYSCTL */ |