[PATCH 1/2] ALSA: usb-audio: Fix potential out-of-bounds shift

From: Takashi Iwai <tiwai@suse.de>
To: alsa-devel@alsa-project.org
Subject: [PATCH 1/2] ALSA: usb-audio: Fix potential out-of-bounds shift
Date: Wed,  9 Dec 2020 09:45:51 +0100	[thread overview]
Message-ID: <20201209084552.17109-1-tiwai@suse.de> (raw)

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>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/usb/format.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sound/usb/format.c b/sound/usb/format.c
index 93459ba228d3..9ebc5d202c87 100644
--- a/sound/usb/format.c
+++ b/sound/usb/format.c
@@ -39,6 +39,8 @@ 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 = 1ULL << format;
-- 
2.26.2

