ALSA: usb-audio: Drop snd_BUG_ON() from snd_usbmidi_output_open()

stable inclusion
from stable-v5.10.156
commit a80369c8ca50bc885d14386087a834659ec54a54
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7MCG1

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a80369c8ca50bc885d14386087a834659ec54a54

--------------------------------

commit ad72c3c3 upstream.

snd_usbmidi_output_open() has a check of the NULL port with
snd_BUG_ON().  snd_BUG_ON() was used as this shouldn't have happened,
but in reality, the NULL port may be seen when the device gives an
invalid endpoint setup at the descriptor, hence the driver skips the
allocation.  That is, the check itself is valid and snd_BUG_ON()
should be dropped from there.  Otherwise it's confusing as if it were
a real bug, as recently syzbot stumbled on it.

Reported-by: syzbot+9abda841d636d86c41da@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/syzbot+9abda841d636d86c41da@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/20221112141223.6144-1-tiwai@suse.deSigned-off-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Nsanglipeng <sanglipeng1@jd.com>

sound/usb/midi.c

@@ -1149,10 +1149,8 @@ static int snd_usbmidi_output_open(struct snd_rawmidi_substream *substream)
 					port = &umidi->endpoints[i].out->ports[j];
 					break;
 				}
-	if (!port) {
-		snd_BUG();
+	if (!port)
 		return -ENXIO;
-	}
 
 	substream->runtime->private_data = port;
 	port->state = STATE_UNKNOWN;