The previous commit 0718a78f6a9f ("ALSA: usb-audio: Kill timer properly at removal") patched a UAF issue caused by the error timer.

However, because the error timer kill added in this patch occurs after the endpoint delete, a race condition to UAF still occurs, albeit rarely.

Additionally, since kill-cleanup for urb is also missing, freed memory can be accessed in interrupt context related to urb, which can cause UAF.

Therefore, to prevent this, error timer and urb must be killed before freeing the heap memory.

Cc: stable@vger.kernel.org Reported-by: syzbot+f02665daa2abeef4a947@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=f02665daa2abeef4a947 Fixes: 0718a78f6a9f ("ALSA: usb-audio: Kill timer properly at removal") Signed-off-by: Jeongjun Park aha310510@gmail.com --- sound/usb/midi.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/sound/usb/midi.c b/sound/usb/midi.c index acb3bf92857c..97e7e7662b12 100644 --- a/sound/usb/midi.c +++ b/sound/usb/midi.c @@ -1522,15 +1522,14 @@ static void snd_usbmidi_free(struct snd_usb_midi *umidi) { int i;

+ if (!umidi->disconnected) + snd_usbmidi_disconnect(&umidi->list); + for (i = 0; i < MIDI_MAX_ENDPOINTS; ++i) { struct snd_usb_midi_endpoint *ep = &umidi->endpoints[i]; - if (ep->out) - snd_usbmidi_out_endpoint_delete(ep->out); - if (ep->in) - snd_usbmidi_in_endpoint_delete(ep->in); + kfree(ep->out); } mutex_destroy(&umidi->mutex); - timer_shutdown_sync(&umidi->error_timer); kfree(umidi); }

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