ALSA: timer: Fix double unlink of active_list

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@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 1 insertions, 1 deletions

diff --git a/sound/core/timer.c b/sound/core/timer.c
index 31f40f03e5b7..9241784dfe7d 100644
--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -694,7 +694,7 @@ 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))