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Date: Thu, 28 Jan 2016 17:17:12 -0800 From: Kamal Mostafa <kamal@...onical.com> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org, kernel-team@...ts.ubuntu.com Cc: Takashi Iwai <tiwai@...e.de>, Kamal Mostafa <kamal@...onical.com> Subject: [PATCH 3.19.y-ckt 094/210] ALSA: seq: Fix race at timer setup and close 3.19.8-ckt14 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Takashi Iwai <tiwai@...e.de> commit 3567eb6af614dac436c4b16a8d426f9faed639b3 upstream. 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@...gle.com> Tested-by: Dmitry Vyukov <dvyukov@...gle.com> Signed-off-by: Takashi Iwai <tiwai@...e.de> Signed-off-by: Kamal Mostafa <kamal@...onical.com> --- sound/core/seq/seq_queue.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/sound/core/seq/seq_queue.c b/sound/core/seq/seq_queue.c index aad4878..52defd8 100644 --- a/sound/core/seq/seq_queue.c +++ b/sound/core/seq/seq_queue.c @@ -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... */ -- 1.9.1
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