From 2f7a26abb8241a0208c68d22815aa247c5ddacab Mon Sep 17 00:00:00 2001

From: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>

Date: Sat, 9 Apr 2022 03:26:55 +0200

Subject: [PATCH] ALSA: pcm: Test for "silence" field in struct "pcm_format_data"

Git-commit: 2f7a26abb8241a0208c68d22815aa247c5ddacab

Patch-mainline: v5.18-rc3

References: git-fixes

Syzbot reports "KASAN: null-ptr-deref Write in

snd_pcm_format_set_silence".[1]

It is due to missing validation of the "silence" field of struct

"pcm_format_data" in "pcm_formats" array.

Add a test for valid "pat" and, if it is not so, return -EINVAL.

[1] https://lore.kernel.org/lkml/000000000000d188ef05dc2c7279@google.com/

Reported-and-tested-by: syzbot+205eb15961852c2c5974@syzkaller.appspotmail.com

Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>

Cc: <stable@vger.kernel.org>

Link: https://lore.kernel.org/r/20220409012655.9399-1-fmdefrancesco@gmail.com

Signed-off-by: Takashi Iwai <tiwai@suse.de>

---

 sound/core/pcm_misc.c | 2 +-

 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/core/pcm_misc.c b/sound/core/pcm_misc.c

index 4866aed97aac..5588b6a1ee8b 100644

--- a/sound/core/pcm_misc.c

+++ b/sound/core/pcm_misc.c

@@ -433,7 +433,7 @@ int snd_pcm_format_set_silence(snd_pcm_format_t format, void *data, unsigned int

 		return 0;

 	width = pcm_formats[(INT)format].phys; /* physical width */

 	pat = pcm_formats[(INT)format].silence;

-	if (! width)

+	if (!width || !pat)

 		return -EINVAL;

 	/* signed or 1 byte data */

 	if (pcm_formats[(INT)format].signd == 1 || width <= 8) {

-- 

2.31.1