ALSA: usb: Fix UBSAN warning in parse_audio_unit()

[ Upstream commit 2f38cf730caedaeacdefb7ff35b0a3c1168117f9 ]

A malformed USB descriptor may pass the lengthy mixer description with
a lot of channels, and this may overflow the 32bit integer shift
size, as caught by syzbot UBSAN test.  Although this won't cause any
real trouble, it's better to address.

This patch introduces a sanity check of the number of channels to bail
out the parsing when too many channels are found.

Reported-by: syzbot+78d5b129a762182225aa@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/0000000000000adac5061d3c7355@google.com
Link: https://patch.msgid.link/20240715123619.26612-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 4b979218d3b027d6022528bba4e1b97572ae92cc..5163d5e7682e7a6e4bbe538d70b3ece045344fd9 100644 (file)
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -2008,6 +2008,13 @@ static int parse_audio_feature_unit(struct mixer_build *state, int unitid,
                bmaControls = ftr->bmaControls;
        }
 
+       if (channels > 32) {
+               usb_audio_info(state->chip,
+                              "usbmixer: too many channels (%d) in unit %d\n",
+                              channels, unitid);
+               return -EINVAL;
+       }
+
        /* parse the source unit */
        err = parse_audio_unit(state, hdr->bSourceID);
        if (err < 0)