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

ALSA: seq: Remove spurious WARN_ON() at timer check

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: alsa-seq-remove-spurious-warn_on-at-timer-check.patch and it can be found in the queue-4.9 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 43a3542870328601be02fcc9d27b09db467336ef Mon Sep 17 00:00:00 2001

From: Takashi Iwai tiwai@suse.de Date: Thu, 30 Nov 2017 10:08:28 +0100 Subject: ALSA: seq: Remove spurious WARN_ON() at timer check

From: Takashi Iwai tiwai@suse.de

commit 43a3542870328601be02fcc9d27b09db467336ef upstream.

The use of snd_BUG_ON() in ALSA sequencer timer may lead to a spurious WARN_ON() when a slave timer is deployed as its backend and a corresponding master timer stops meanwhile. The symptom was triggered by syzkaller spontaneously.

Since the NULL timer is valid there, rip off snd_BUG_ON().

Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- sound/core/seq/seq_timer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/sound/core/seq/seq_timer.c +++ b/sound/core/seq/seq_timer.c @@ -355,7 +355,7 @@ static int initialize_timer(struct snd_s unsigned long freq;

t = tmr->timeri->timer; - if (snd_BUG_ON(!t)) + if (!t) return -EINVAL;

freq = tmr->preferred_resolution;

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

queue-4.9/alsa-seq-remove-spurious-warn_on-at-timer-check.patch queue-4.9/alsa-pcm-prevent-uaf-in-snd_pcm_info.patch queue-4.9/alsa-usb-audio-add-check-return-value-for-usb_string.patch queue-4.9/alsa-usb-audio-fix-out-of-bound-error.patch