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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.

Change-Id: I95e2ab06180dfe43fb6b7c2875a866b53ca245ce
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>
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tiwai authored and andi34 committed Jan 13, 2016
1 parent 4521c04 commit 254a325245aaaaa2543a75c48613e4360bdb9aa2
Showing with 1 addition and 1 deletion.
  1. +1 −1 sound/core/timer.c
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@@ -689,7 +689,7 @@ 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))

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