Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 533 insertions, 0 deletions

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 <linux/export.h>
+#include <linux/list_sort.h>
+#include <linux/ref_tracker.h>
+#include <linux/slab.h>
+#include <linux/stacktrace.h>
+#include <linux/stackdepot.h>
+#include <linux/seq_file.h>
+
+#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 <linux/xarray.h>
+
+/*
+ * 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 <linux/debugfs.h>
+
+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 */