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[PATCH 3/4] tracing: Fix use-after-free in hist_unreg_all/hist_enable_unreg_all

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From: Steven Rostedt <rostedt@goodmis.org>

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().

Link: http://lkml.kernel.org/r/c3d05b79e42555b6e36a3a99aae0e37315ee5304.1467247517.git.tom.zanussi@linux.intel.com

Cc: Dmitry Vyukov <dvyukov@google.com>
[Copied Steve's hist_enable_unreg_all() fix to hist_unreg_all()]
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 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 0c05b8a99806..19ae135120a3 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);
-- 
2.8.1

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[PATCH 3/4] tracing: Fix use-after-free in hist_unreg_all/hist_enable_unreg_all Steven Rostedt <rostedt@goodmis.org> - 2016-08-03 16:00 +0200
  Re: [PATCH 3/4] tracing: Fix use-after-free in hist_unreg_all/hist_enable_unreg_all Dmitry Vyukov <dvyukov@google.com> - 2016-08-03 16:30 +0200
    Re: [PATCH 3/4] tracing: Fix use-after-free in  hist_unreg_all/hist_enable_unreg_all Steven Rostedt <rostedt@goodmis.org> - 2016-08-03 17:50 +0200

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