From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- lib/ref_tracker.c | 533 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 533 insertions(+) create mode 100644 lib/ref_tracker.c (limited to 'lib/ref_tracker.c') diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c new file mode 100644 index 000000000..30c999d57 --- /dev/null +++ b/lib/ref_tracker.c @@ -0,0 +1,533 @@ +// SPDX-License-Identifier: GPL-2.0-or-later + +#define pr_fmt(fmt) "ref_tracker: " fmt + +#include +#include +#include +#include +#include +#include +#include + +#define REF_TRACKER_STACK_ENTRIES 16 +#define STACK_BUF_SIZE 1024 + +struct ref_tracker { + struct list_head head; /* anchor into dir->list or dir->quarantine */ + bool dead; + depot_stack_handle_t alloc_stack_handle; + depot_stack_handle_t free_stack_handle; +}; + +struct ref_tracker_dir_stats { + int total; + int count; + struct { + depot_stack_handle_t stack_handle; + unsigned int count; + } stacks[]; +}; + +#ifdef CONFIG_DEBUG_FS +#include + +/* + * ref_tracker_dir_init() is usually called in allocation-safe contexts, but + * the same is not true of ref_tracker_dir_exit() which can be called from + * anywhere an object is freed. Removing debugfs dentries is a blocking + * operation, so we defer that work to the debugfs_reap_worker. + * + * Each dentry is tracked in the appropriate xarray. When + * ref_tracker_dir_exit() is called, its entries in the xarrays are marked and + * the workqueue job is scheduled. The worker then runs and deletes any marked + * dentries asynchronously. + */ +static struct xarray debugfs_dentries; +static struct xarray debugfs_symlinks; +static struct work_struct debugfs_reap_worker; + +#define REF_TRACKER_DIR_DEAD XA_MARK_0 +static inline void ref_tracker_debugfs_mark(struct ref_tracker_dir *dir) +{ + unsigned long flags; + + xa_lock_irqsave(&debugfs_dentries, flags); + __xa_set_mark(&debugfs_dentries, (unsigned long)dir, REF_TRACKER_DIR_DEAD); + xa_unlock_irqrestore(&debugfs_dentries, flags); + + xa_lock_irqsave(&debugfs_symlinks, flags); + __xa_set_mark(&debugfs_symlinks, (unsigned long)dir, REF_TRACKER_DIR_DEAD); + xa_unlock_irqrestore(&debugfs_symlinks, flags); + + schedule_work(&debugfs_reap_worker); +} +#else +static inline void ref_tracker_debugfs_mark(struct ref_tracker_dir *dir) +{ +} +#endif + +static struct ref_tracker_dir_stats * +ref_tracker_get_stats(struct ref_tracker_dir *dir, unsigned int limit) +{ + struct ref_tracker_dir_stats *stats; + struct ref_tracker *tracker; + + stats = kmalloc_flex(*stats, stacks, limit, GFP_NOWAIT); + if (!stats) + return ERR_PTR(-ENOMEM); + stats->total = 0; + stats->count = 0; + + list_for_each_entry(tracker, &dir->list, head) { + depot_stack_handle_t stack = tracker->alloc_stack_handle; + int i; + + ++stats->total; + for (i = 0; i < stats->count; ++i) + if (stats->stacks[i].stack_handle == stack) + break; + if (i >= limit) + continue; + if (i >= stats->count) { + stats->stacks[i].stack_handle = stack; + stats->stacks[i].count = 0; + ++stats->count; + } + ++stats->stacks[i].count; + } + + return stats; +} + +struct ostream { + void __ostream_printf (*func)(struct ostream *stream, char *fmt, ...); + char *prefix; + char *buf; + struct seq_file *seq; + int size, used; +}; + +static void __ostream_printf pr_ostream_log(struct ostream *stream, char *fmt, ...) +{ + va_list args; + + va_start(args, fmt); + vprintk(fmt, args); + va_end(args); +} + +static void __ostream_printf pr_ostream_buf(struct ostream *stream, char *fmt, ...) +{ + int ret, len = stream->size - stream->used; + va_list args; + + va_start(args, fmt); + ret = vsnprintf(stream->buf + stream->used, len, fmt, args); + va_end(args); + if (ret > 0) + stream->used += min(ret, len); +} + +#define pr_ostream(stream, fmt, args...) \ +({ \ + struct ostream *_s = (stream); \ +\ + _s->func(_s, fmt, ##args); \ +}) + +static void +__ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir, + unsigned int display_limit, struct ostream *s) +{ + struct ref_tracker_dir_stats *stats; + unsigned int i = 0, skipped; + depot_stack_handle_t stack; + char *sbuf; + + lockdep_assert_held(&dir->lock); + + if (list_empty(&dir->list)) + return; + + stats = ref_tracker_get_stats(dir, display_limit); + if (IS_ERR(stats)) { + pr_ostream(s, "%s%s@%p: couldn't get stats, error %pe\n", + s->prefix, dir->class, dir, stats); + return; + } + + sbuf = kmalloc(STACK_BUF_SIZE, GFP_NOWAIT); + + for (i = 0, skipped = stats->total; i < stats->count; ++i) { + stack = stats->stacks[i].stack_handle; + if (sbuf && !stack_depot_snprint(stack, sbuf, STACK_BUF_SIZE, 4)) + sbuf[0] = 0; + pr_ostream(s, "%s%s@%p has %d/%d users at\n%s\n", s->prefix, + dir->class, dir, stats->stacks[i].count, + stats->total, sbuf); + skipped -= stats->stacks[i].count; + } + + if (skipped) + pr_ostream(s, "%s%s@%p skipped reports about %d/%d users.\n", + s->prefix, dir->class, dir, skipped, stats->total); + + kfree(sbuf); + + kfree(stats); +} + +void ref_tracker_dir_print_locked(struct ref_tracker_dir *dir, + unsigned int display_limit) +{ + struct ostream os = { .func = pr_ostream_log, + .prefix = "ref_tracker: " }; + + __ref_tracker_dir_pr_ostream(dir, display_limit, &os); +} +EXPORT_SYMBOL(ref_tracker_dir_print_locked); + +void ref_tracker_dir_print(struct ref_tracker_dir *dir, + unsigned int display_limit) +{ + unsigned long flags; + + spin_lock_irqsave(&dir->lock, flags); + ref_tracker_dir_print_locked(dir, display_limit); + spin_unlock_irqrestore(&dir->lock, flags); +} +EXPORT_SYMBOL(ref_tracker_dir_print); + +int ref_tracker_dir_snprint(struct ref_tracker_dir *dir, char *buf, size_t size) +{ + struct ostream os = { .func = pr_ostream_buf, + .prefix = "ref_tracker: ", + .buf = buf, + .size = size }; + unsigned long flags; + + spin_lock_irqsave(&dir->lock, flags); + __ref_tracker_dir_pr_ostream(dir, 16, &os); + spin_unlock_irqrestore(&dir->lock, flags); + + return os.used; +} +EXPORT_SYMBOL(ref_tracker_dir_snprint); + +void ref_tracker_dir_exit(struct ref_tracker_dir *dir) +{ + struct ref_tracker *tracker, *n; + unsigned long flags; + bool leak = false; + + dir->dead = true; + /* + * The xarray entries must be marked before the dir->lock is taken to + * protect simultaneous debugfs readers. + */ + ref_tracker_debugfs_mark(dir); + spin_lock_irqsave(&dir->lock, flags); + list_for_each_entry_safe(tracker, n, &dir->quarantine, head) { + list_del(&tracker->head); + kfree(tracker); + dir->quarantine_avail++; + } + if (!list_empty(&dir->list)) { + ref_tracker_dir_print_locked(dir, 16); + leak = true; + list_for_each_entry_safe(tracker, n, &dir->list, head) { + list_del(&tracker->head); + kfree(tracker); + } + } + spin_unlock_irqrestore(&dir->lock, flags); + WARN_ON_ONCE(leak); + WARN_ON_ONCE(refcount_read(&dir->untracked) != 1); + WARN_ON_ONCE(refcount_read(&dir->no_tracker) != 1); +} +EXPORT_SYMBOL(ref_tracker_dir_exit); + +int ref_tracker_alloc(struct ref_tracker_dir *dir, + struct ref_tracker **trackerp, + gfp_t gfp) +{ + unsigned long entries[REF_TRACKER_STACK_ENTRIES]; + struct ref_tracker *tracker; + unsigned int nr_entries; + gfp_t gfp_mask = gfp | __GFP_NOWARN; + unsigned long flags; + + WARN_ON_ONCE(dir->dead); + + if (!trackerp) { + refcount_inc(&dir->no_tracker); + return 0; + } + if (gfp & __GFP_DIRECT_RECLAIM) + gfp_mask |= __GFP_NOFAIL; + *trackerp = tracker = kzalloc_obj(*tracker, gfp_mask); + if (unlikely(!tracker)) { + pr_err_once("memory allocation failure, unreliable refcount tracker.\n"); + refcount_inc(&dir->untracked); + return -ENOMEM; + } + nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 1); + tracker->alloc_stack_handle = stack_depot_save(entries, nr_entries, gfp); + + spin_lock_irqsave(&dir->lock, flags); + list_add(&tracker->head, &dir->list); + spin_unlock_irqrestore(&dir->lock, flags); + return 0; +} +EXPORT_SYMBOL_GPL(ref_tracker_alloc); + +int ref_tracker_free(struct ref_tracker_dir *dir, + struct ref_tracker **trackerp) +{ + unsigned long entries[REF_TRACKER_STACK_ENTRIES]; + depot_stack_handle_t stack_handle; + struct ref_tracker *tracker; + unsigned int nr_entries; + unsigned long flags; + + WARN_ON_ONCE(dir->dead); + + if (!trackerp) { + refcount_dec(&dir->no_tracker); + return 0; + } + tracker = *trackerp; + if (!tracker) { + refcount_dec(&dir->untracked); + return -EEXIST; + } + nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 1); + stack_handle = stack_depot_save(entries, nr_entries, + GFP_NOWAIT); + + spin_lock_irqsave(&dir->lock, flags); + if (tracker->dead) { + pr_err("reference already released.\n"); + if (tracker->alloc_stack_handle) { + pr_err("allocated in:\n"); + stack_depot_print(tracker->alloc_stack_handle); + } + if (tracker->free_stack_handle) { + pr_err("freed in:\n"); + stack_depot_print(tracker->free_stack_handle); + } + spin_unlock_irqrestore(&dir->lock, flags); + WARN_ON_ONCE(1); + return -EINVAL; + } + tracker->dead = true; + + tracker->free_stack_handle = stack_handle; + + list_move_tail(&tracker->head, &dir->quarantine); + if (!dir->quarantine_avail) { + tracker = list_first_entry(&dir->quarantine, struct ref_tracker, head); + list_del(&tracker->head); + } else { + dir->quarantine_avail--; + tracker = NULL; + } + spin_unlock_irqrestore(&dir->lock, flags); + + kfree(tracker); + return 0; +} +EXPORT_SYMBOL_GPL(ref_tracker_free); + +#ifdef CONFIG_DEBUG_FS +#include + +static struct dentry *ref_tracker_debug_dir = (struct dentry *)-ENOENT; + +static void __ostream_printf pr_ostream_seq(struct ostream *stream, char *fmt, ...) +{ + va_list args; + + va_start(args, fmt); + seq_vprintf(stream->seq, fmt, args); + va_end(args); +} + +static int ref_tracker_dir_seq_print(struct ref_tracker_dir *dir, struct seq_file *seq) +{ + struct ostream os = { .func = pr_ostream_seq, + .prefix = "", + .seq = seq }; + + __ref_tracker_dir_pr_ostream(dir, 16, &os); + + return os.used; +} + +static int ref_tracker_debugfs_show(struct seq_file *f, void *v) +{ + struct ref_tracker_dir *dir = f->private; + unsigned long index = (unsigned long)dir; + unsigned long flags; + int ret; + + /* + * "dir" may not exist at this point if ref_tracker_dir_exit() has + * already been called. Take care not to dereference it until its + * legitimacy is established. + * + * The xa_lock is necessary to ensure that "dir" doesn't disappear + * before its lock can be taken. If it's in the hash and not marked + * dead, then it's safe to take dir->lock which prevents + * ref_tracker_dir_exit() from completing. Once the dir->lock is + * acquired, the xa_lock can be released. All of this must be IRQ-safe. + */ + xa_lock_irqsave(&debugfs_dentries, flags); + if (!xa_load(&debugfs_dentries, index) || + xa_get_mark(&debugfs_dentries, index, REF_TRACKER_DIR_DEAD)) { + xa_unlock_irqrestore(&debugfs_dentries, flags); + return -ENODATA; + } + + spin_lock(&dir->lock); + xa_unlock(&debugfs_dentries); + ret = ref_tracker_dir_seq_print(dir, f); + spin_unlock_irqrestore(&dir->lock, flags); + return ret; +} + +static int ref_tracker_debugfs_open(struct inode *inode, struct file *filp) +{ + struct ref_tracker_dir *dir = inode->i_private; + + return single_open(filp, ref_tracker_debugfs_show, dir); +} + +static const struct file_operations ref_tracker_debugfs_fops = { + .owner = THIS_MODULE, + .open = ref_tracker_debugfs_open, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, +}; + +/** + * ref_tracker_dir_debugfs - create debugfs file for ref_tracker_dir + * @dir: ref_tracker_dir to be associated with debugfs file + * + * In most cases, a debugfs file will be created automatically for every + * ref_tracker_dir. If the object was created before debugfs is brought up + * then that may fail. In those cases, it is safe to call this at a later + * time to create the file. + */ +void ref_tracker_dir_debugfs(struct ref_tracker_dir *dir) +{ + char name[NAME_MAX + 1]; + struct dentry *dentry; + int ret; + + /* No-op if already created */ + dentry = xa_load(&debugfs_dentries, (unsigned long)dir); + if (dentry && !xa_is_err(dentry)) + return; + + ret = snprintf(name, sizeof(name), "%s@%p", dir->class, dir); + name[sizeof(name) - 1] = '\0'; + + if (ret < sizeof(name)) { + dentry = debugfs_create_file(name, S_IFREG | 0400, + ref_tracker_debug_dir, dir, + &ref_tracker_debugfs_fops); + if (!IS_ERR(dentry)) { + void *old; + + old = xa_store_irq(&debugfs_dentries, (unsigned long)dir, + dentry, GFP_KERNEL); + + if (xa_is_err(old)) + debugfs_remove(dentry); + else + WARN_ON_ONCE(old); + } + } +} +EXPORT_SYMBOL(ref_tracker_dir_debugfs); + +void __ostream_printf ref_tracker_dir_symlink(struct ref_tracker_dir *dir, const char *fmt, ...) +{ + char name[NAME_MAX + 1]; + struct dentry *symlink, *dentry; + va_list args; + int ret; + + symlink = xa_load(&debugfs_symlinks, (unsigned long)dir); + dentry = xa_load(&debugfs_dentries, (unsigned long)dir); + + /* Already created?*/ + if (symlink && !xa_is_err(symlink)) + return; + + if (!dentry || xa_is_err(dentry)) + return; + + va_start(args, fmt); + ret = vsnprintf(name, sizeof(name), fmt, args); + va_end(args); + name[sizeof(name) - 1] = '\0'; + + if (ret < sizeof(name)) { + symlink = debugfs_create_symlink(name, ref_tracker_debug_dir, + dentry->d_name.name); + if (!IS_ERR(symlink)) { + void *old; + + old = xa_store_irq(&debugfs_symlinks, (unsigned long)dir, + symlink, GFP_KERNEL); + if (xa_is_err(old)) + debugfs_remove(symlink); + else + WARN_ON_ONCE(old); + } + } +} +EXPORT_SYMBOL(ref_tracker_dir_symlink); + +static void debugfs_reap_work(struct work_struct *work) +{ + struct dentry *dentry; + unsigned long index; + bool reaped; + + do { + reaped = false; + xa_for_each_marked(&debugfs_symlinks, index, dentry, REF_TRACKER_DIR_DEAD) { + xa_erase_irq(&debugfs_symlinks, index); + debugfs_remove(dentry); + reaped = true; + } + xa_for_each_marked(&debugfs_dentries, index, dentry, REF_TRACKER_DIR_DEAD) { + xa_erase_irq(&debugfs_dentries, index); + debugfs_remove(dentry); + reaped = true; + } + } while (reaped); +} + +static int __init ref_tracker_debugfs_postcore_init(void) +{ + INIT_WORK(&debugfs_reap_worker, debugfs_reap_work); + xa_init_flags(&debugfs_dentries, XA_FLAGS_LOCK_IRQ); + xa_init_flags(&debugfs_symlinks, XA_FLAGS_LOCK_IRQ); + return 0; +} +postcore_initcall(ref_tracker_debugfs_postcore_init); + +static int __init ref_tracker_debugfs_late_init(void) +{ + ref_tracker_debug_dir = debugfs_create_dir("ref_tracker", NULL); + return 0; +} +late_initcall(ref_tracker_debugfs_late_init); +#endif /* CONFIG_DEBUG_FS */ -- cgit v1.3.1