From: Takashi Iwai Date: Sat, 8 Aug 2026 15:20:06 +0000 (+0200) Subject: ALSA: usb: Fix UAF at delayed release of MIDI2 EPs X-Git-Tag: v7.2~20^2~2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f8a80cfb68613fb7e6452b66447dbc63f435d140;p=thirdparty%2Fkernel%2Flinux.git ALSA: usb: Fix UAF at delayed release of MIDI2 EPs The recent fix for UAF in ump_to_endpoint() caused another UAF because it tries to dereference the UMP endpoint object, but this might be executed at a delayed context where the endpoint has been already released. Add private_free to clear the associated data for avoiding the further dereference for delayed releases. Fixes: 4a05b2d1b464 ("ALSA: usb-audio: fix use-after-free in ump_to_endpoint()") Reported-by: syzbot+565b1138cfbe549d4422@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=565b1138cfbe549d4422 Cc: Link: https://patch.msgid.link/20260808152009.1947835-1-tiwai@suse.de Signed-off-by: Takashi Iwai --- diff --git a/sound/usb/midi2.c b/sound/usb/midi2.c index 83980fb83ac8..1dc78f536ef9 100644 --- a/sound/usb/midi2.c +++ b/sound/usb/midi2.c @@ -677,6 +677,14 @@ static int parse_midi_2_0_endpoints(struct snd_usb_midi2_interface *umidi) return 0; } +static void free_ump_private_data(struct snd_ump_endpoint *ump) +{ + struct snd_usb_midi2_ump *rmidi = ump->private_data; + + if (rmidi) + rmidi->ump = NULL; +} + static void free_all_midi2_umps(struct snd_usb_midi2_interface *umidi) { struct snd_usb_midi2_ump *rmidi; @@ -727,6 +735,7 @@ static int create_midi2_ump(struct snd_usb_midi2_interface *umidi, ump->private_data = rmidi; ump->ops = &snd_usb_midi_v2_ump_ops; + ump->private_free = free_ump_private_data; rmidi->eps[STR_IN] = ep_in; rmidi->eps[STR_OUT] = ep_out;