Patch "ALSA: seq: Fix race at timer setup and close" has been added to the 3.18-stable tree

Patch "ALSA: seq: Fix race at timer setup and close" has been added to the 3.18-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    ALSA: seq: Fix race at timer setup and close

to the 3.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     alsa-seq-fix-race-at-timer-setup-and-close.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 3567eb6af614dac436c4b16a8d426f9faed639b3 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Tue, 12 Jan 2016 15:36:27 +0100
Subject: ALSA: seq: Fix race at timer setup and close

From: Takashi Iwai <tiwai@suse.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@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/core/seq/seq_queue.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/sound/core/seq/seq_queue.c
+++ b/sound/core/seq/seq_queue.c
@@ -142,8 +142,10 @@ static struct snd_seq_queue *queue_new(i
 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... */


Patches currently in stable-queue which might be from tiwai@suse.de are

queue-3.18/alsa-timer-fix-leak-in-events-via-snd_timer_user_ccallback.patch
queue-3.18/alsa-timer-fix-leak-in-sndrv_timer_ioctl_params.patch
queue-3.18/alsa-timer-fix-race-among-timer-ioctls.patch
queue-3.18/alsa-timer-fix-leak-in-events-via-snd_timer_user_tinterrupt.patch
queue-3.18/alsa-seq-fix-race-at-timer-setup-and-close.patch