linux-kernel - [PATCH 3.2 096/140] ALSA: pcm: Remove yet superfluous WARN

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Date:   Wed, 28 Feb 2018 15:20:22 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Takashi Iwai" <tiwai@...e.de>,
        syzbot+7e6ee55011deeebce15d@...kaller.appspotmail.com
Subject: [PATCH 3.2 096/140] ALSA: pcm: Remove yet superfluous WARN_ON()

3.2.100-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@...e.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@...kaller.appspotmail.com
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 sound/core/pcm_lib.c | 1 -
 1 file changed, 1 deletion(-)

--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -590,7 +590,6 @@ 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;
 	}