ALSA: seq: Fix race at timer setup and close

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.

Change-Id: I58773978b545fb73311e2eab973ab63c9099dba1
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 committed by Flex1911
parent 39cd3354c6
commit 6e47c42f2a

View file

@ -144,8 +144,10 @@ 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... */