[2/5] tracing/user_events: Track refcount consistently via put/get

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 34aa0a5d8e2a..8f0fb6cb0f33 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -175,6 +175,28 @@  static u32 user_event_key(char *name)
 	return jhash(name, strlen(name), 0);
 }
 
+static struct user_event *user_event_get(struct user_event *user)
+{
+	refcount_inc(&user->refcnt);
+
+	return user;
+}
+
+static void user_event_put(struct user_event *user, bool locked)
+{
+#ifdef CONFIG_LOCKDEP
+	if (locked)
+		lockdep_assert_held(&event_mutex);
+	else
+		lockdep_assert_not_held(&event_mutex);
+#endif
+
+	if (unlikely(!user))
+		return;
+
+	refcount_dec(&user->refcnt);
+}
+
 static void user_event_group_destroy(struct user_event_group *group)
 {
 	kfree(group->system_name);
@@ -258,12 +280,13 @@  static struct user_event_group
 	return NULL;
 };
 
-static void user_event_enabler_destroy(struct user_event_enabler *enabler)
+static void user_event_enabler_destroy(struct user_event_enabler *enabler,
+				       bool locked)
 {
 	list_del_rcu(&enabler->link);
 
 	/* No longer tracking the event via the enabler */
-	refcount_dec(&enabler->event->refcnt);
+	user_event_put(enabler->event, locked);
 
 	kfree(enabler);
 }
@@ -325,7 +348,7 @@  static void user_event_enabler_fault_fixup(struct work_struct *work)
 
 	/* User asked for enabler to be removed during fault */
 	if (test_bit(ENABLE_VAL_FREEING_BIT, ENABLE_BITOPS(enabler))) {
-		user_event_enabler_destroy(enabler);
+		user_event_enabler_destroy(enabler, true);
 		goto out;
 	}
 
@@ -489,13 +512,12 @@  static bool user_event_enabler_dup(struct user_event_enabler *orig,
 	if (!enabler)
 		return false;
 
-	enabler->event = orig->event;
+	enabler->event = user_event_get(orig->event);
 	enabler->addr = orig->addr;
 
 	/* Only dup part of value (ignore future flags, etc) */
 	enabler->values = orig->values & ENABLE_VAL_DUP_MASK;
 
-	refcount_inc(&enabler->event->refcnt);
 	list_add_rcu(&enabler->link, &mm->enablers);
 
 	return true;
@@ -595,7 +617,7 @@  static void user_event_mm_destroy(struct user_event_mm *mm)
 	struct user_event_enabler *enabler, *next;
 
 	list_for_each_entry_safe(enabler, next, &mm->enablers, link)
-		user_event_enabler_destroy(enabler);
+		user_event_enabler_destroy(enabler, false);
 
 	mmdrop(mm->mm);
 	kfree(mm);
@@ -748,7 +770,7 @@  static struct user_event_enabler
 	 * exit or run exec(), which includes forks and clones.
 	 */
 	if (!*write_result) {
-		refcount_inc(&enabler->event->refcnt);
+		user_event_get(user);
 		list_add_rcu(&enabler->link, &user_mm->enablers);
 	}
 
@@ -1336,10 +1358,8 @@  static struct user_event *find_user_event(struct user_event_group *group,
 	*outkey = key;
 
 	hash_for_each_possible(group->register_table, user, node, key)
-		if (!strcmp(EVENT_NAME(user), name)) {
-			refcount_inc(&user->refcnt);
-			return user;
-		}
+		if (!strcmp(EVENT_NAME(user), name))
+			return user_event_get(user);
 
 	return NULL;
 }
@@ -1553,12 +1573,12 @@  static int user_event_reg(struct trace_event_call *call,
 
 	return ret;
 inc:
-	refcount_inc(&user->refcnt);
+	user_event_get(user);
 	update_enable_bit_for(user);
 	return 0;
 dec:
 	update_enable_bit_for(user);
-	refcount_dec(&user->refcnt);
+	user_event_put(user, true);
 	return 0;
 }
 
@@ -1592,7 +1612,7 @@  static int user_event_create(const char *raw_command)
 	ret = user_event_parse_cmd(group, name, &user, 0);
 
 	if (!ret)
-		refcount_dec(&user->refcnt);
+		user_event_put(user, false);
 
 	mutex_unlock(&group->reg_mutex);
 
@@ -1856,7 +1876,7 @@  static int delete_user_event(struct user_event_group *group, char *name)
 	if (!user)
 		return -ENOENT;
 
-	refcount_dec(&user->refcnt);
+	user_event_put(user, true);
 
 	if (!user_event_last_ref(user))
 		return -EBUSY;
@@ -2015,9 +2035,7 @@  static int user_events_ref_add(struct user_event_file_info *info,
 	for (i = 0; i < count; ++i)
 		new_refs->events[i] = refs->events[i];
 
-	new_refs->events[i] = user;
-
-	refcount_inc(&user->refcnt);
+	new_refs->events[i] = user_event_get(user);
 
 	rcu_assign_pointer(info->refs, new_refs);
 
@@ -2131,7 +2149,7 @@  static long user_events_ioctl_reg(struct user_event_file_info *info,
 	ret = user_events_ref_add(info, user);
 
 	/* No longer need parse ref, ref_add either worked or not */
-	refcount_dec(&user->refcnt);
+	user_event_put(user, false);
 
 	/* Positive number is index and valid */
 	if (ret < 0)
@@ -2280,7 +2298,7 @@  static long user_events_ioctl_unreg(unsigned long uarg)
 			set_bit(ENABLE_VAL_FREEING_BIT, ENABLE_BITOPS(enabler));
 
 			if (!test_bit(ENABLE_VAL_FAULTING_BIT, ENABLE_BITOPS(enabler)))
-				user_event_enabler_destroy(enabler);
+				user_event_enabler_destroy(enabler, true);
 
 			/* Removed at least one */
 			ret = 0;
@@ -2337,7 +2355,6 @@  static int user_events_release(struct inode *node, struct file *file)
 	struct user_event_file_info *info = file->private_data;
 	struct user_event_group *group;
 	struct user_event_refs *refs;
-	struct user_event *user;
 	int i;
 
 	if (!info)
@@ -2361,12 +2378,9 @@  static int user_events_release(struct inode *node, struct file *file)
 	 * The underlying user_events are ref counted, and cannot be freed.
 	 * After this decrement, the user_events may be freed elsewhere.
 	 */
-	for (i = 0; i < refs->count; ++i) {
-		user = refs->events[i];
+	for (i = 0; i < refs->count; ++i)
+		user_event_put(refs->events[i], false);
 
-		if (user)
-			refcount_dec(&user->refcnt);
-	}
 out:
 	file->private_data = NULL;