From 22098763a10d9c1340827fcf6edab66f153b27f0 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 13 Sep 2026 12:27:00 -0700 Subject: Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Don't destroy user event fields when removal fails User event fields are destroyed before the event is removed from visibility. But that can fail leaving the still visible event with no fields. Move the destroying of the fields to after the event is successfully removed from visibility. - Initialize function graph state is fork before calling copy_exec_state() For non-CLONE_VM forks, copy_exec_state() allocates a new task_exec_state. If that allocation fails, ftrace_graph_exit_task() will free the tasks ret_stack pointer. Since that pointer is still using the parent's ret_stack, it mistakenly frees the parent's pointer too. Call ftrace_graph_init() on the task first which will NULL out the new tasks's ret_stack and if the copy fails, it will not free anything. - Remove FGRAPH_MAX_INDEX The macro FGRAPH_MAX_INDEX was added but never used. Remove it. - Save ent_size in function graph printing of nested functions The function graph tracer needs to look at the next event to see if the next event is the return of the current function entry. If it is, it prints a single line: ktime_get(); Otherwise it prints it like a nested function: tick_nohz_irq_exit() { ktime_get(); kcpustat_irq_exit(); } In order to look at the next event, it must save the current event so that it has the information to print from it. It saves the event in the iterator descriptor called "ent". What it doesn't save is the ent_size of the event which is now used to know if the function graph arguments are to be printed. The peek doesn't save the size so the size used happens to be that of the size of the last event that was seen. Save the entry event size in the iterator descriptor so that the correct size is used. - Fix several errors with freeing data in the histogram code The histogram code had a lot of leaked or or incorrect accounting when failures happen. Correct them. - Fix histogram regression of .percent and .graph modifiers Up until 6.3 histogram values could have "percent" or "graph" modifiers that changed how they were printed. But a change that added restricting histograms values from being strings, stack traces and other modifiers inadvertently prevented them from using the percent and graph modifiers, which were legal use cases for values. Put back the percent and graph modifiers. - Fix various typos in the comments - Set the trace_clock before initializing a histogram with clock argument The histogram API allows the user to specific which trace clock to use via a "clock=" string. The histogram is set up first before the clock is checked. If the passed in clock is not valid, it exits without fully fixing up the histogram leaving it on the list and a use-after-free can trigger. Update the clock argument first and if it fails then exit gracefully before the histogram trigger is placed on any lists. - Restore :mod: trailer after parsing in ftrace_set_clr_event The function ftrace_set_clr_event() modifies the parse string and needs to put it back to what was passed in. It searches for ":mod:" via a strsep() but fails to put back the first ':' in the string. Add back the ':' in the passed in string. - Take trace_array reference when opening a tracer options file The options files are dynamically created and some tracers add their own options. When a tracer adds their own list of options, the trace_array holding them has an array to hold the list of options for each tracer. This array increases in size via a krealloc(), and the new entry gets a newly allocated array to hold the options of the new tracer being added. The element in each entry of the tracer's option array holds a pointer back to the trace_array, a pointer to the tracer it is associated to, a pointer to the flags of the option. The issue is that these arrays are freed when the trace_array is freed when its instance it represents is removed from the instances directory. There's a race that an open of one of these options files can happen when the instance is being removed. Add a new helper function to be called by the open function of the options file to iterate all existing trace_arrays under a lock and find the one that has the given option element in one of it's tracer arrays. If found, then update the associated trace_array's reference counter to keep it from being freed. If not found, have the open call return -ENODEV. - Disable interrupts when acquiring the lock in rb_wake_up_waiters() The function rb_wake_up_waiters() assumes it will be called in interrupt context and does not disable irqs when taking cpu_buffer->reader_lock, which can be called in hard interrupt context. The issue is in PREEMPT_RT, this function is called in thread context leaving this lock open to a deadlock. Take the lock with interrupts disabled. - Use rcu_assign_pointer() for tmp_ops filter hash The tmp_ops used in update_ftrace_direct_mod() assigns its filter_hash field directly, but that field is annotated as __rcu and sparse complains. Assign it with rcu_assign_pointer() - Fix use-after-free in enable_trigger_private_data_free() The trace_event_call is accessed through the event_trigger_data's trace_event_file pointer to put the trace_event_call on freeing. The issue is that the trace_event_file data may have been freed already causing a use-after-free. Add a field to the event_trigger_data that points directly to the trace_event_call so that it can decrement its reference directly without needing to go through the trace_event_file. - Fix accounting of buffer data remote headers trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount the number of pages is needed for the asked for size as it doesn't take into account the meta data on each page. Add a helper function to do the calculation properly and use that in these functions. - Catch nr_page_va overflow in ring_buffer_desc sizing The number of pages per remote ring buffer is capped by ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to overflow that field would silently allocate a descriptor smaller than what was asked for. - Do not resize the subbuf order if any per_cpu buffer is disabled The mmapping of ring buffers disables resizing the subbuffers, but it is done per-cpu whereas the subbuf size change is done for all the per_cpu buffers under the buffer->mutex. It could change the size of some while the mapping is happening on others. Have the resize of the subbuf order check all the per_cpu buffers under the lock to see if any of them is disabled before starting and causing an inconsistency between buffers that are being mapped. * tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits) ring-buffer: Check resize_disabled before publishing the new subbuf order tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing tracing/remotes: Account for ring buffer page header in size calculation tracing: Don't dereference trace_event_file in deferred trigger free ftrace: Use rcu_assign_pointer() for tmp_ops filter hash ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters() tracing: Take trace_array reference when opening a tracer options file tracing: Fix ring_buffer_read_page_size() kernel-doc tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event() tracing: Fix memory corruption from a "STACKTRACE" histogram key tracing: Fix memory corruption from the histogram stacktrace modifier tracing: Undo the registration when enabling the histogram trigger fails tracing: Take the reference before publishing the named histogram trigger tracing: Set the trace clock before registering the histogram trigger tracing: Fix typo "preceeded" in comment tracing: Fix typo "availabe" in comment tracing: Let histogram values keep the percent and graph modifiers tracing: Keep the entry count when the histogram stats allocation fails tracing: Free histogram the field rejected for a bad modifier tracing: Free histogram the var ref when its initialization fails ... --- 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