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Commit 6a54979c authored by Takashi Iwai's avatar Takashi Iwai Committed by Greg Kroah-Hartman
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ALSA: usb-audio: Clear MIDI port active flag after draining 



commit 0665886ad1392e6b5bae85d7a6ccbed48dca1522 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: default avatar <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.de


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 9c99aacf

sound/usb/midi.c

+1 −0
Original line number Diff line number Diff line
@@ -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);

}