From: Takashi Iwai <tiwai@suse.de>
Date: Wed, 9 Dec 2020 08:45:51 +0000 (+0100)
Subject: ALSA: usb-audio: Fix potential out-of-bounds shift
X-Git-Tag: v4.4.249~116
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=03f13b8b5d61c5a886fa42dafe61de47aaf44c0d;p=thirdparty%2Fkernel%2Fstable.git

ALSA: usb-audio: Fix potential out-of-bounds shift

commit 43d5ca88dfcd35e43010fdd818e067aa9a55f5ba upstream.

syzbot spotted a potential out-of-bounds shift in the USB-audio format
parser that receives the arbitrary shift value from the USB
descriptor.

Add a range check for avoiding the undefined behavior.

Reported-by: syzbot+df7dc146ebdd6435eea3@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201209084552.17109-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/sound/usb/format.c b/sound/usb/format.c
index f28a41194d171..ca75807eeb170 100644
--- a/sound/usb/format.c
+++ b/sound/usb/format.c
@@ -52,6 +52,8 @@ static u64 parse_audio_format_i_type(struct snd_usb_audio *chip,
 	case UAC_VERSION_1:
 	default: {
 		struct uac_format_type_i_discrete_descriptor *fmt = _fmt;
+		if (format >= 64)
+			return 0; /* invalid format */
 		sample_width = fmt->bBitResolution;
 		sample_bytes = fmt->bSubframeSize;
 		format = 1 << format;