6.6-stable review patch. If anyone has any objections, please let me know.
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From: Takashi Iwai tiwai@suse.de
[ Upstream commit a3bdd8f5c2217e1cb35db02c2eed36ea20fb50f5 ]
We fixed the UAF issue in USB MIDI code by canceling the pending work at closing each MIDI output device in the commit below. However, this assumed that it's the only one that is tied with the endpoint, and it resulted in unexpected data truncations when multiple devices are assigned to a single endpoint and opened simultaneously.
For addressing the unexpected MIDI message drops, simply replace cancel_work_sync() with flush_work(). The drain callback should have been already invoked before the close callback, hence the port->active flag must be already cleared. So this just assures that the pending work is finished before freeing the resources.
Fixes: 0125de38122f ("ALSA: usb-audio: Cancel pending work at closing a MIDI substream") Reported-and-tested-by: John Keeping jkeeping@inmusicbrands.com Closes: https://lore.kernel.org/20250217111647.3368132-1-jkeeping@inmusicbrands.com Link: https://patch.msgid.link/20250218114024.23125-1-tiwai@suse.de Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Sasha Levin sashal@kernel.org --- sound/usb/midi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/sound/usb/midi.c b/sound/usb/midi.c index 6b0993258e039..6d861046b582b 100644 --- a/sound/usb/midi.c +++ b/sound/usb/midi.c @@ -1145,7 +1145,7 @@ 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); + flush_work(&port->ep->work); return substream_open(substream, 0, 0); }