[PATCH 4.9 020/175] ALSA: usb-audio: Fix potential out-of-bounds shift

Greg Kroah-Hartman
2020-12-28T16:37:43Z

From: Takashi Iwai <tiwai@suse.de>

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>

---
sound/usb/format.c | 2 ++
1 file changed, 2 insertions(+)

--- a/sound/usb/format.c
+++ b/sound/usb/format.c
@@ -52,6 +52,8 @@ static u64 parse_audio_format_i_type(str
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;