Patch "ALSA: seq: Remove spurious WARN_ON() at timer check" has been added to the 4.9-stable tree

Patch "ALSA: seq: Remove spurious WARN_ON() at timer check" has been added to the 4.9-stable tree

[gregkh]

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;a=summary

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