[PATCH 3.13.y-ckt 071/136] ALSA: timer: Fix double unlink of active_list

From: Kamal Mostafa
Date: Tue Feb 02 2016 - 13:46:43 EST


3.13.11-ckt34 -stable review patch. If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Takashi Iwai <tiwai@xxxxxxx>

commit ee8413b01045c74340aa13ad5bdf905de32be736 upstream.

ALSA timer instance object has a couple of linked lists and they are
unlinked unconditionally at snd_timer_stop(). Meanwhile
snd_timer_interrupt() unlinks it, but it calls list_del() which leaves
the element list itself unchanged. This ends up with unlinking twice,
and it was caught by syzkaller fuzzer.

The fix is to use list_del_init() variant properly there, too.

Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Tested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
sound/core/timer.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/core/timer.c b/sound/core/timer.c
index 6ddcf06..3bd05d9 100644
--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -693,7 +693,7 @@ void snd_timer_interrupt(struct snd_timer * timer, unsigned long ticks_left)
} else {
ti->flags &= ~SNDRV_TIMER_IFLG_RUNNING;
if (--timer->running)
- list_del(&ti->active_list);
+ list_del_init(&ti->active_list);
}
if ((timer->hw.flags & SNDRV_TIMER_HW_TASKLET) ||
(ti->flags & SNDRV_TIMER_IFLG_FAST))
--
1.9.1