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 eeb56d6fe8aa84f5ab1e3fe8f62c3af375593a82..06190e3fd9194d5ff82c9398ac2e5e3ab1d88aa6 100644 (file)
--- 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;