[PATCH] ALSA: usb-audio: Cancel pending work at closing a MIDI substream

[Takashi Iwai]

At closing a USB MIDI output substream, there might be still a pending
work, which would eventually access the rawmidi runtime object that is
being released.  For fixing the race, make sure to cancel the pending
work at closing.

Reported-by: syzbot+6912c9592caca7ca0e7d at syzkaller.appspotmail.com
Cc: <stable at vger.kernel.org>
Link: https://lore.kernel.org/r/000000000000e7e75005dfd07cf6@google.com
Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 sound/usb/midi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/usb/midi.c b/sound/usb/midi.c
index 7c6ca2b433a5..344fbeadf161 100644
--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -1145,6 +1145,9 @@ static int snd_usbmidi_output_open(struct snd_rawmidi_substream *substream)
 
 static int snd_usbmidi_output_close(struct snd_rawmidi_substream *substream)
 {
+	struct usbmidi_out_port *port = substream->runtime->private_data;
+
+	cancel_work_sync(&port->ep->work);
 	return substream_open(substream, 0, 0);
 }
 
-- 
2.35.3