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ALSA: seq: Fix race at timer setup and close

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ALSA sequencer code has an open race between the timer setup ioctl and
the close of the client.  This was triggered by syzkaller fuzzer, and
a use-after-free was caught there as a result.

This patch papers over it by adding a proper queue->timer_mutex lock
around the timer-related calls in the relevant code path.

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>
This commit is contained in:
Takashi Iwai 2016-01-12 15:36:27 +01:00
parent 030e2c78d3
commit 3567eb6af6
1 changed files with 2 additions and 0 deletions
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2
sound/core/seq/seq_queue.c
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@ -142,8 +142,10 @@ static struct snd_seq_queue *queue_new(int owner, int locked)
static void queue_delete(struct snd_seq_queue *q)
{
/* stop and release the timer */
mutex_lock(&q->timer_mutex);
snd_seq_timer_stop(q->timer);
snd_seq_timer_close(q);
mutex_unlock(&q->timer_mutex);
/* wait until access free */
snd_use_lock_sync(&q->use_lock);
/* release resources... */