[PATCH 1/2] tracing: Fix use-after-free in hist_unreg_all/hist_enable_unreg_all

[Tom Zanussi]

From: Steven Rostedt <rostedt@xxxxxxxxxxx>

While running tools/testing/selftests test suite with KASAN, Dmitry
Vyukov hit the following use-after-free report:

  ==================================================================
  BUG: KASAN: use-after-free in hist_unreg_all+0x1a1/0x1d0 at addr
  ffff880031632cc0
  Read of size 8 by task ftracetest/7413
  ==================================================================
  BUG kmalloc-128 (Not tainted): kasan: bad access detected
  ------------------------------------------------------------------

This fixes the problem, along with the same problem in
hist_enable_unreg_all().

Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
[Copied Steve's hist_enable_unreg_all() fix to hist_unreg_all()]
Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
---
 kernel/trace/trace_events_hist.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 0c05b8a..19ae135 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1500,9 +1500,9 @@ static void hist_unregister_trigger(char *glob, struct event_trigger_ops *ops,
 
 static void hist_unreg_all(struct trace_event_file *file)
 {
-	struct event_trigger_data *test;
+	struct event_trigger_data *test, *n;
 
-	list_for_each_entry_rcu(test, &file->triggers, list) {
+	list_for_each_entry_safe(test, n, &file->triggers, list) {
 		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
 			list_del_rcu(&test->list);
 			trace_event_trigger_enable_disable(file, 0);
@@ -1699,9 +1699,9 @@ hist_enable_get_trigger_ops(char *cmd, char *param)
 
 static void hist_enable_unreg_all(struct trace_event_file *file)
 {
-	struct event_trigger_data *test;
+	struct event_trigger_data *test, *n;
 
-	list_for_each_entry_rcu(test, &file->triggers, list) {
+	list_for_each_entry_safe(test, n, &file->triggers, list) {
 		if (test->cmd_ops->trigger_type == ETT_HIST_ENABLE) {
 			list_del_rcu(&test->list);
 			update_cond_flag(file);
-- 
1.9.3