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

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>

diff --git a/sound/usb/format.c b/sound/usb/format.c
index 93459ba228d3ac339942542b2eae8a6b06145a05..9ebc5d202c87398fa4e622acd58295d6bc356df3 100644 (file)
--- 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;