ALSA: usb-audio: Kill timer properly at removal

The USB-audio MIDI code initializes the timer, but in a rare case, the
driver might be freed without the disconnect call.  This leaves the
timer in an active state while the assigned object is released via
snd_usbmidi_free(), which ends up with a kernel warning when the debug
configuration is enabled, as spotted by fuzzer.

For avoiding the problem, put timer_shutdown_sync() at
snd_usbmidi_free(), so that the timer can be killed properly.
While we're at it, replace the existing timer_delete_sync() at the
disconnect callback with timer_shutdown_sync(), too.

Reported-by: syzbot+d8f72178ab6783a7daea@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/681c70d7.050a0220.a19a9.00c6.GAE@google.com
Cc: <stable@vger.kernel.org>
Link: https://patch.msgid.link/20250519212031.14436-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Author: tiwai

sound/usb/midi.c

@@ -1530,6 +1530,7 @@ static void snd_usbmidi_free(struct snd_usb_midi *umidi)
 			snd_usbmidi_in_endpoint_delete(ep->in);
 	}
 	mutex_destroy(&umidi->mutex);
+	timer_shutdown_sync(&umidi->error_timer);
 	kfree(umidi);
 }
 
@@ -1553,7 +1554,7 @@ void snd_usbmidi_disconnect(struct list_head *p)
 	spin_unlock_irq(&umidi->disc_lock);
 	up_write(&umidi->disc_rwsem);
 
-	timer_delete_sync(&umidi->error_timer);
+	timer_shutdown_sync(&umidi->error_timer);
 
 	for (i = 0; i < MIDI_MAX_ENDPOINTS; ++i) {
 		struct snd_usb_midi_endpoint *ep = &umidi->endpoints[i];