From 4352b8aee98005853aa63f57d6377282de17a33f Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 23 Aug 2026 13:28:57 -0700 Subject: Merge tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux Pull I3C updates from Alexandre Belloni: "A new driver this cycle, for the AMD AXI I3C controller. There are also new features such as IBI wakeup support, SETAASA device discovery and ACPI support for the the DAA methods, meaning we can now communicate with the SPD devices on DDR5 modules. New driver: - AMD AXI I3C master controller Subsystem: - I3C Common Command Code (CCC) handling improvements, especially around GET CCCs - SETAASA device discovery support - ACPI support for all existing DAA methods like SETDASA, SETNEWDA as well as I2C devices on I3C bus - IBI-based wakeup support Drivers: - dw: SETAASA support - mipi-i3c-hci: advertise IBI wakeup capability, AMD_PT I3C controller support, PIO queue management support for HCI v1.2 - renesas: improve suspend to RAM support, add runtime PM support" * tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux: (70 commits) i3c: dw: reduce do_daa time if there's no client i3c: mipi-i3c-hci: Add support for AMD_PT I3C controller i3c: mipi-i3c-hci: Add PIO queue management support for HCI v1.2 i3c: mipi-i3c-hci: Fix missing STAT_IBI_STATUS_THLD in PIO mode i3c: dw: rename "pclk" to "apb" to match dt-binding i3c: dw: make struct dw_i3c_cmd smaller i3c: dw: use COMMAND_PORT_TRANSFER_ARG instead of hardcoding i3c: renesas: Don't register devices when ENTDAA times out i3c: master: dw-i3c-master: fix OD timing for first broadcast i3c: mipi-i3c-hci: Advertise IBI wakeup capability i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev() i3c: mipi-i3c-hci-pci: Propagate I3C wakeup requirements to PCI i3c: master: Reject IBI requests from non-IBI-capable devices i3c: master: Add helper to query bus wakeup requirements i3c: master: Report wakeup events for IBIs i3c: master: Support IBI-based wakeup capability i3c: master: Fix potential UAF in i3c_device_match() i3c: master: Fix potential UAF in i3c_device_uevent() i3c: Make dev->desc locking assumptions explicit i3c: master: Fix use-after-free of master->this ... --- fs/d_path.c | 450 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 450 insertions(+) create mode 100644 fs/d_path.c (limited to 'fs/d_path.c') diff --git a/fs/d_path.c b/fs/d_path.c new file mode 100644 index 000000000..c25309006 --- /dev/null +++ b/fs/d_path.c @@ -0,0 +1,450 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include +#include +#include +#include +#include +#include +#include +#include "mount.h" +#include "internal.h" + +struct prepend_buffer { + char *buf; + int len; +}; +#define DECLARE_BUFFER(__name, __buf, __len) \ + struct prepend_buffer __name = {.buf = __buf + __len, .len = __len} + +static char *extract_string(struct prepend_buffer *p) +{ + if (likely(p->len >= 0)) + return p->buf; + return ERR_PTR(-ENAMETOOLONG); +} + +static bool prepend_char(struct prepend_buffer *p, unsigned char c) +{ + if (likely(p->len > 0)) { + p->len--; + *--p->buf = c; + return true; + } + p->len = -1; + return false; +} + +/* + * The source of the prepend data can be an optimistic load + * of a dentry name and length. And because we don't hold any + * locks, the length and the pointer to the name may not be + * in sync if a concurrent rename happens, and the kernel + * copy might fault as a result. + * + * The end result will correct itself when we check the + * rename sequence count, but we need to be able to handle + * the fault gracefully. + */ +static bool prepend_copy(void *dst, const void *src, int len) +{ + if (unlikely(copy_from_kernel_nofault(dst, src, len))) { + memset(dst, 'x', len); + return false; + } + return true; +} + +static bool prepend(struct prepend_buffer *p, const char *str, int namelen) +{ + // Already overflowed? + if (p->len < 0) + return false; + + // Will overflow? + if (p->len < namelen) { + // Fill as much as possible from the end of the name + str += namelen - p->len; + p->buf -= p->len; + prepend_copy(p->buf, str, p->len); + p->len = -1; + return false; + } + + // Fits fully + p->len -= namelen; + p->buf -= namelen; + return prepend_copy(p->buf, str, namelen); +} + +/** + * prepend_name - prepend a pathname in front of current buffer pointer + * @p: prepend buffer which contains buffer pointer and allocated length + * @name: name string and length qstr structure + * + * With RCU path tracing, it may race with d_move(). Use READ_ONCE() to + * make sure that either the old or the new name pointer and length are + * fetched. However, there may be mismatch between length and pointer. + * But since the length cannot be trusted, we need to copy the name very + * carefully when doing the prepend_copy(). It also prepends "/" at + * the beginning of the name. The sequence number check at the caller will + * retry it again when a d_move() does happen. So any garbage in the buffer + * due to mismatched pointer and length will be discarded. + * + * Load acquire is needed to make sure that we see the new name data even + * if we might get the length wrong. + */ +static bool prepend_name(struct prepend_buffer *p, const struct qstr *name) +{ + const char *dname = smp_load_acquire(&name->name); /* ^^^ */ + u32 dlen = READ_ONCE(name->len); + + return prepend(p, dname, dlen) && prepend_char(p, '/'); +} + +static int __prepend_path(const struct dentry *dentry, const struct mount *mnt, + const struct path *root, struct prepend_buffer *p) +{ + while (dentry != root->dentry || &mnt->mnt != root->mnt) { + const struct dentry *parent = READ_ONCE(dentry->d_parent); + + if (dentry == mnt->mnt.mnt_root) { + struct mount *m = READ_ONCE(mnt->mnt_parent); + struct mnt_namespace *mnt_ns; + + if (likely(mnt != m)) { + dentry = READ_ONCE(mnt->mnt_mountpoint); + mnt = m; + continue; + } + /* Global root */ + mnt_ns = READ_ONCE(mnt->mnt_ns); + /* open-coded is_mounted() to use local mnt_ns */ + if (!IS_ERR_OR_NULL(mnt_ns) && !is_anon_ns(mnt_ns)) + return 1; // absolute root + else + return 2; // detached or not attached yet + } + + if (unlikely(dentry == parent)) + /* Escaped? */ + return 3; + + prefetch(parent); + if (!prepend_name(p, &dentry->d_name)) + break; + dentry = parent; + } + return 0; +} + +/** + * prepend_path - Prepend path string to a buffer + * @path: the dentry/vfsmount to report + * @root: root vfsmnt/dentry + * @p: prepend buffer which contains buffer pointer and allocated length + * + * The function will first try to write out the pathname without taking any + * lock other than the RCU read lock to make sure that dentries won't go away. + * It only checks the sequence number of the global rename_lock as any change + * in the dentry's d_seq will be preceded by changes in the rename_lock + * sequence number. If the sequence number had been changed, it will restart + * the whole pathname back-tracing sequence again by taking the rename_lock. + * In this case, there is no need to take the RCU read lock as the recursive + * parent pointer references will keep the dentry chain alive as long as no + * rename operation is performed. + */ +static int prepend_path(const struct path *path, + const struct path *root, + struct prepend_buffer *p) +{ + unsigned seq, m_seq = 0; + struct prepend_buffer b; + int error; + + rcu_read_lock(); +restart_mnt: + read_seqbegin_or_lock(&mount_lock, &m_seq); + seq = 0; + rcu_read_lock(); +restart: + b = *p; + read_seqbegin_or_lock(&rename_lock, &seq); + error = __prepend_path(path->dentry, real_mount(path->mnt), root, &b); + if (!(seq & 1)) + rcu_read_unlock(); + if (need_seqretry(&rename_lock, seq)) { + seq = 1; + goto restart; + } + done_seqretry(&rename_lock, seq); + + if (!(m_seq & 1)) + rcu_read_unlock(); + if (need_seqretry(&mount_lock, m_seq)) { + m_seq = 1; + goto restart_mnt; + } + done_seqretry(&mount_lock, m_seq); + + if (unlikely(error == 3)) + b = *p; + + if (b.len == p->len) + prepend_char(&b, '/'); + + *p = b; + return error; +} + +/** + * __d_path - return the path of a dentry + * @path: the dentry/vfsmount to report + * @root: root vfsmnt/dentry + * @buf: buffer to return value in + * @buflen: buffer length + * + * Convert a dentry into an ASCII path name. + * + * Returns a pointer into the buffer or an error code if the + * path was too long. + * + * "buflen" should be positive. + * + * If the path is not reachable from the supplied root, return %NULL. + */ +char *__d_path(const struct path *path, + const struct path *root, + char *buf, int buflen) +{ + DECLARE_BUFFER(b, buf, buflen); + + prepend_char(&b, 0); + if (unlikely(prepend_path(path, root, &b) > 0)) + return NULL; + return extract_string(&b); +} + +char *d_absolute_path(const struct path *path, + char *buf, int buflen) +{ + struct path root = {}; + DECLARE_BUFFER(b, buf, buflen); + + prepend_char(&b, 0); + if (unlikely(prepend_path(path, &root, &b) > 1)) + return ERR_PTR(-EINVAL); + return extract_string(&b); +} + +static void get_fs_root_rcu(struct fs_struct *fs, struct path *root) +{ + unsigned seq; + + do { + seq = read_seqbegin(&fs->seq); + *root = fs->root; + } while (read_seqretry(&fs->seq, seq)); +} + +/** + * d_path - return the path of a dentry + * @path: path to report + * @buf: buffer to return value in + * @buflen: buffer length + * + * Convert a dentry into an ASCII path name. If the entry has been deleted + * the string " (deleted)" is appended. Note that this is ambiguous. + * + * Returns a pointer into the buffer or an error code if the path was + * too long. Note: Callers should use the returned pointer, not the passed + * in buffer, to use the name! The implementation often starts at an offset + * into the buffer, and may leave 0 bytes at the start. + * + * "buflen" should be positive. + */ +char *d_path(const struct path *path, char *buf, int buflen) +{ + DECLARE_BUFFER(b, buf, buflen); + struct path root; + + /* + * We have various synthetic filesystems that never get mounted. On + * these filesystems dentries are never used for lookup purposes, and + * thus don't need to be hashed. They also don't need a name until a + * user wants to identify the object in /proc/pid/fd/. The little hack + * below allows us to generate a name for these objects on demand: + * + * Some pseudo inodes are mountable. When they are mounted + * path->dentry == path->mnt->mnt_root. In that case don't call d_dname + * and instead have d_path return the mounted path. + */ + if (path->dentry->d_op && path->dentry->d_op->d_dname && + (!IS_ROOT(path->dentry) || path->dentry != path->mnt->mnt_root || + failfs_mnt(path->mnt))) + return path->dentry->d_op->d_dname(path->dentry, buf, buflen); + + rcu_read_lock(); + get_fs_root_rcu(current->fs, &root); + if (unlikely(d_unlinked(path->dentry))) + prepend(&b, " (deleted)", 11); + else + prepend_char(&b, 0); + prepend_path(path, &root, &b); + rcu_read_unlock(); + + return extract_string(&b); +} +EXPORT_SYMBOL(d_path); + +/* + * Helper function for dentry_operations.d_dname() members + */ +char *dynamic_dname(char *buffer, int buflen, const char *fmt, ...) +{ + va_list args; + char *start; + int sz; + + va_start(args, fmt); + sz = vsnprintf(buffer, buflen, fmt, args) + 1; + va_end(args); + + if (sz > NAME_MAX || sz > buflen) + return ERR_PTR(-ENAMETOOLONG); + + /* Move the formatted d_name to the end of the buffer. */ + start = buffer + (buflen - sz); + return memmove(start, buffer, sz); +} + +char *simple_dname(struct dentry *dentry, char *buffer, int buflen) +{ + DECLARE_BUFFER(b, buffer, buflen); + /* these dentries are never renamed, so d_lock is not needed */ + prepend(&b, " (deleted)", 11); + prepend(&b, dentry->d_name.name, dentry->d_name.len); + prepend_char(&b, '/'); + return extract_string(&b); +} + +/* + * Write full pathname from the root of the filesystem into the buffer. + */ +static char *__dentry_path(const struct dentry *d, struct prepend_buffer *p) +{ + const struct dentry *dentry; + struct prepend_buffer b; + int seq = 0; + + rcu_read_lock(); +restart: + dentry = d; + b = *p; + read_seqbegin_or_lock(&rename_lock, &seq); + while (!IS_ROOT(dentry)) { + const struct dentry *parent = dentry->d_parent; + + prefetch(parent); + if (!prepend_name(&b, &dentry->d_name)) + break; + dentry = parent; + } + if (!(seq & 1)) + rcu_read_unlock(); + if (need_seqretry(&rename_lock, seq)) { + seq = 1; + goto restart; + } + done_seqretry(&rename_lock, seq); + if (b.len == p->len) + prepend_char(&b, '/'); + return extract_string(&b); +} + +char *dentry_path_raw(const struct dentry *dentry, char *buf, int buflen) +{ + DECLARE_BUFFER(b, buf, buflen); + + prepend_char(&b, 0); + return __dentry_path(dentry, &b); +} +EXPORT_SYMBOL(dentry_path_raw); + +char *dentry_path(const struct dentry *dentry, char *buf, int buflen) +{ + DECLARE_BUFFER(b, buf, buflen); + + if (unlikely(d_unlinked(dentry))) + prepend(&b, "//deleted", 10); + else + prepend_char(&b, 0); + return __dentry_path(dentry, &b); +} + +static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root, + struct path *pwd) +{ + unsigned seq; + + do { + seq = read_seqbegin(&fs->seq); + *root = fs->root; + *pwd = fs->pwd; + } while (read_seqretry(&fs->seq, seq)); +} + +/* + * NOTE! The user-level library version returns a + * character pointer. The kernel system call just + * returns the length of the buffer filled (which + * includes the ending '\0' character), or a negative + * error value. So libc would do something like + * + * char *getcwd(char * buf, size_t size) + * { + * int retval; + * + * retval = sys_getcwd(buf, size); + * if (retval >= 0) + * return buf; + * errno = -retval; + * return NULL; + * } + */ +SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) +{ + int error; + struct path pwd, root; + char *page = __getname(); + + if (!page) + return -ENOMEM; + + rcu_read_lock(); + get_fs_root_and_pwd_rcu(current->fs, &root, &pwd); + + if (unlikely(d_unlinked(pwd.dentry))) { + rcu_read_unlock(); + error = -ENOENT; + } else { + unsigned len; + DECLARE_BUFFER(b, page, PATH_MAX); + + prepend_char(&b, 0); + if (unlikely(prepend_path(&pwd, &root, &b) > 0)) + prepend(&b, "(unreachable)", 13); + rcu_read_unlock(); + + len = PATH_MAX - b.len; + if (unlikely(len > PATH_MAX)) + error = -ENAMETOOLONG; + else if (unlikely(len > size)) + error = -ERANGE; + else if (copy_to_user(buf, b.buf, len)) + error = -EFAULT; + else + error = len; + } + __putname(page); + return error; +} -- cgit v1.3.1