ALSA: usb-audio: Fix UBSAN warnings for MIDI jacks

The calculation of in_cables and out_cables bitmaps are done with the
bit shift by the value from the descriptor, which is an arbitrary
value, and can lead to UBSAN shift-out-of-bounds warnings.

Fix it by filtering the bad descriptor values with the check of the
upper bound 0x10 (the cable bitmaps are 16 bits).

Reported-by: syzbot+92e45ae45543f89e8c88@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201223174557.10249-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/midi.c b/sound/usb/midi.c
index c821365..0c23fa6 100644 (file)
--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -1889,6 +1889,8 @@ static int snd_usbmidi_get_ms_info(struct snd_usb_midi *umidi,
                ms_ep = find_usb_ms_endpoint_descriptor(hostep);
                if (!ms_ep)
                        continue;
+               if (ms_ep->bNumEmbMIDIJack > 0x10)
+                       continue;
                if (usb_endpoint_dir_out(ep)) {
                        if (endpoints[epidx].out_ep) {
                                if (++epidx >= MIDI_MAX_ENDPOINTS) {
@@ -2141,6 +2143,8 @@ static int snd_usbmidi_detect_roland(struct snd_usb_midi *umidi,
                    cs_desc[1] == USB_DT_CS_INTERFACE &&
                    cs_desc[2] == 0xf1 &&
                    cs_desc[3] == 0x02) {
+                       if (cs_desc[4] > 0x10 || cs_desc[5] > 0x10)
+                               continue;
                        endpoint->in_cables  = (1 << cs_desc[4]) - 1;
                        endpoint->out_cables = (1 << cs_desc[5]) - 1;
                        return snd_usbmidi_detect_endpoints(umidi, endpoint, 1);