linux-kernel - Re: [PATCH 3/4] tracing: Fix use-after-free in hist_unreg_all/hist_enable_unreg

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Date:	Wed, 3 Aug 2016 16:19:53 +0200
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tom Zanussi <tom.zanussi@...ux.intel.com>
Subject: Re: [PATCH 3/4] tracing: Fix use-after-free in hist_unreg_all/hist_enable_unreg_all

On Wed, Aug 3, 2016 at 3:54 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
> From: Steven Rostedt <rostedt@...dmis.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@...gle.com>

s/Cc/Reported-by/ please

> [Copied Steve's hist_enable_unreg_all() fix to hist_unreg_all()]
> Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.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
>
>