From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753710AbcBAL3U (ORCPT ); Mon, 1 Feb 2016 06:29:20 -0500 Received: from mx2.suse.de ([195.135.220.15]:52870 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753439AbcBAL3S (ORCPT ); Mon, 1 Feb 2016 06:29:18 -0500 Date: Mon, 01 Feb 2016 12:29:14 +0100 Message-ID: From: Takashi Iwai To: Dmitry Vyukov Cc: alsa-devel@alsa-project.org, Jie Yang , Mark Brown , Jaroslav Kysela , Takashi Sakamoto , LKML , Alexander Potapenko , Kostya Serebryany , syzkaller , Sasha Levin Subject: Re: sound: use-after-free in snd_seq_deliver_single_event In-Reply-To: References: User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/24.5 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 01 Feb 2016 12:12:21 +0100, Dmitry Vyukov wrote: > > > Looks like a race at closing virmidi device. > > Does the patch below fix it? > > > This seems to help. Thanks for a quick test. FWIW, below is the final patch I'm going to queue. Takashi -- 8< -- From: Takashi Iwai Subject: [PATCH] ALSA: seq: Fix race at closing in virmidi driver The virmidi driver has an open race at closing its assigned rawmidi device, and this may lead to use-after-free in snd_seq_deliver_single_event(). Plug the hole by properly protecting the linked list deletion and calling in the right order in snd_virmidi_input_close(). BugLink: http://lkml.kernel.org/r/CACT4Y+Zd66+w12fNN85-425cVQT=K23kWbhnCEcMB8s3us-Frw@mail.gmail.com Reported-by: Dmitry Vyukov Tested-by: Dmitry Vyukov Cc: Signed-off-by: Takashi Iwai --- sound/core/seq/seq_virmidi.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/sound/core/seq/seq_virmidi.c b/sound/core/seq/seq_virmidi.c index 3da2d48610b3..f71aedfb408c 100644 --- a/sound/core/seq/seq_virmidi.c +++ b/sound/core/seq/seq_virmidi.c @@ -254,9 +254,13 @@ static int snd_virmidi_output_open(struct snd_rawmidi_substream *substream) */ static int snd_virmidi_input_close(struct snd_rawmidi_substream *substream) { + struct snd_virmidi_dev *rdev = substream->rmidi->private_data; struct snd_virmidi *vmidi = substream->runtime->private_data; - snd_midi_event_free(vmidi->parser); + + write_lock_irq(&rdev->filelist_lock); list_del(&vmidi->list); + write_unlock_irq(&rdev->filelist_lock); + snd_midi_event_free(vmidi->parser); substream->runtime->private_data = NULL; kfree(vmidi); return 0; -- 2.7.0