On Tue, 19 Apr 2022 11:01:47 +0200, Takashi Iwai wrote: > > On Mon, 18 Apr 2022 12:12:23 +0200, > syzbot wrote: > > > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: a19944809fe9 Merge tag 'hardening-v5.18-rc3' of git://git... > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=16a40ae0f00000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=eb177500e563582f > > dashboard link: https://syzkaller.appspot.com/bug?extid=70e777a39907d6d5fd0a > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1590dfa8f00000 > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+70e777a39907d6d5fd0a@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > ================================================================== > > BUG: KASAN: use-after-free in __snd_rawmidi_transmit_peek+0x261/0x360 sound/core/rawmidi.c:1286 > > Looks like a leftover work. The fix patch is below. On the second thought, this would be rather in a different code path, and the fix should be smaller like below. Let's see. Takashi -- 8< -- From: Takashi Iwai <tiwai@xxxxxxx> Subject: [PATCH] ALSA: usb-audio: Clear MIDI port active flag after draining 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: syzbot+70e777a39907d6d5fd0a@xxxxxxxxxxxxxxxxxxxxxxxxx Cc: <stable@xxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/00000000000011555605dceaff03@xxxxxxxxxx Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> --- sound/usb/midi.c | 1 + 1 file changed, 1 insertion(+) diff --git a/sound/usb/midi.c b/sound/usb/midi.c index 2c01649c70f6..7c6ca2b433a5 100644 --- a/sound/usb/midi.c +++ b/sound/usb/midi.c @@ -1194,6 +1194,7 @@ 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); } -- 2.34.1
