Patch "ALSA: pcm: Remove yet superfluous WARN_ON()" has been added to the 3.18-stable tree

Patch "ALSA: pcm: Remove yet superfluous WARN_ON()" 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: pcm: Remove yet superfluous WARN_ON()

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-pcm-remove-yet-superfluous-warn_on.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 23b19b7b50fe1867da8d431eea9cd3e4b6328c2c Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Wed, 10 Jan 2018 23:48:05 +0100
Subject: ALSA: pcm: Remove yet superfluous WARN_ON()

From: Takashi Iwai <tiwai@suse.de>

commit 23b19b7b50fe1867da8d431eea9cd3e4b6328c2c upstream.

muldiv32() contains a snd_BUG_ON() (which is morphed as WARN_ON() with
debug option) for checking the case of 0 / 0.  This would be helpful
if this happens only as a logical error; however, since the hw refine
is performed with any data set provided by user, the inconsistent
values that can trigger such a condition might be passed easily.
Actually, syzbot caught this by passing some zero'ed old hw_params
ioctl.

So, having snd_BUG_ON() there is simply superfluous and rather
harmful to give unnecessary confusions.  Let's get rid of it.

Reported-by: syzbot+7e6ee55011deeebce15d@syzkaller.appspotmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/core/pcm_lib.c |    1 -
 1 file changed, 1 deletion(-)

--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -644,7 +644,6 @@ static inline unsigned int muldiv32(unsi
 {
 	u_int64_t n = (u_int64_t) a * b;
 	if (c == 0) {
-		snd_BUG_ON(!n);
 		*r = 0;
 		return UINT_MAX;
 	}


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

queue-3.18/alsa-pcm-remove-yet-superfluous-warn_on.patch
queue-3.18/alsa-hda-apply-the-existing-quirk-to-imac-14-1.patch