Re: [syzbot] [sound?] [usb?] UBSAN: shift-out-of-bounds in parse_audio_unit

[Edward Adam Davis]

invalid bControlSize and bLength make channels too large

#syz test: upstream a19ea421490d

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 409fc1164694..17081ada6802 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -2000,6 +2000,8 @@ static int parse_audio_feature_unit(struct mixer_build *state, int unitid,
 	if (state->mixer->protocol == UAC_VERSION_1) {
 		csize = hdr->bControlSize;
 		channels = (hdr->bLength - 7) / csize - 1;
+		if (channels > 32)
+			return -EINVAL;
 		bmaControls = hdr->bmaControls;
 	} else if (state->mixer->protocol == UAC_VERSION_2) {
 		struct uac2_feature_unit_descriptor *ftr = _ftr;