ALSA: usb-audio: Clear MIDI port active flag after draining

stable inclusion
from stable-v5.10.113
commit 8ce3820fc9d496100fb39008a952eebfb695b060
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5ISAH

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8ce3820fc9d496100fb39008a952eebfb695b060

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

commit 0665886a upstream.

When a rawmidi output stream is closed, it calls the drain at first,
then does trigger-off only when the drain returns -ERESTARTSYS as a
fallback.  It implies that each driver should turn off the stream
properly after the drain.  Meanwhile, USB-audio MIDI interface didn't
change the port->active flag after the drain.  This may leave the
output work picking up the port that is closed right now, which
eventually leads to a use-after-free for the already released rawmidi
object.

This patch fixes the bug by properly clearing the port->active flag
after the output drain.

Reported-by: syzbot+70e777a39907d6d5fd0a@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/00000000000011555605dceaff03@google.com
Link: https://lore.kernel.org/r/20220420130247.22062-1-tiwai@suse.deSigned-off-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

sound/usb/midi.c

@@ -1210,6 +1210,7 @@ static void snd_usbmidi_output_drain(struct snd_rawmidi_substream *substream)
 		} while (drain_urbs && timeout);
 		finish_wait(&ep->drain_wait, &wait);
 	}
+	port->active = 0;
 	spin_unlock_irq(&ep->buffer_lock);
 }