linux-kernel - Re: trace: use-after-free in hist_unreg

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Date:	Tue, 28 Jun 2016 10:43:09 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Dmitry Vyukov <dvyukov@...gle.com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Tom Zanussi <tom.zanussi@...ux.intel.com>
Subject: Re: trace: use-after-free in hist_unreg_all

On Tue, 28 Jun 2016 14:58:50 +0200
Dmitry Vyukov <dvyukov@...gle.com> wrote:

> Hello,
> 
> While running tools/testing/selftests test suite with KASAN I 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
> -----------------------------------------------------------------------------

Thanks for the report. Can you check if this patch fixes the issue?

-- Steve

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 0c05b8a99806..948adb4b6761 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -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);