From mboxrd@z Thu Jan  1 00:00:00 1970
From: Takashi Iwai <tiwai@suse.de>
Subject: Re: sound: use-after-free in snd_timer_interrupt
Date: Fri, 15 Jan 2016 12:00:05 +0100
Message-ID: <s5hwprbt8ei.wl-tiwai@suse.de>
References: <CACT4Y+ZrVvE3dgcYHRdHDG0X316VgC-=pr2U-233vVn_QbHZHw@mail.gmail.com>
	<s5hwprdv2sp.wl-tiwai@suse.de>
	<CACT4Y+ZFsNxsVyq_n6kh=HN1dStj_hL=B9eUu4heAHes=ixf3g@mail.gmail.com>
	<s5hio2xmh9z.wl-tiwai@suse.de>
	<CACT4Y+bqxg_C7JmnUSRm_9jiZ9R9XqbBV0igDdUW1ZhtqvktJw@mail.gmail.com>
	<CACT4Y+anWgMKQmNByifCs+-jizRQL9twxvRQzW3XzNJ8+a6fDw@mail.gmail.com>
	<s5hegdlmdd6.wl-tiwai@suse.de>
	<CACT4Y+Y62DTncEAb_S6JykY7Ps7SHo2QyCopMObBxJt2fB_NKA@mail.gmail.com>
	<s5h60yxmc99.wl-tiwai@suse.de>
	<s5ha8o8uoqb.wl-tiwai@suse.de>
	<CACT4Y+a-=mrGALS+yf4GwGmJGLWXVJ0mbucPAkZ7WSGFaSR0Kw@mail.gmail.com>
Mime-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka")
Content-Type: text/plain; charset=US-ASCII
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <CACT4Y+a-=mrGALS+yf4GwGmJGLWXVJ0mbucPAkZ7WSGFaSR0Kw@mail.gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
To: Dmitry Vyukov <dvyukov@google.com>
Cc: alsa-devel@alsa-project.org, Jie Yang <yang.jie@intel.com>, Mark Brown <broonie@kernel.org>, Jaroslav Kysela <perex@perex.cz>, LKML <linux-kernel@vger.kernel.org>, Eric Dumazet <edumazet@google.com>, Alexander Potapenko <glider@google.com>, Kostya Serebryany <kcc@google.com>, syzkaller <syzkaller@googlegroups.com>, Sasha Levin <sasha.levin@oracle.com>
List-Id: alsa-devel@alsa-project.org

On Fri, 15 Jan 2016 09:06:10 +0100,
Dmitry Vyukov wrote:
> 
> On Thu, Jan 14, 2016 at 5:09 PM, Takashi Iwai <tiwai@suse.de> wrote:
> > On Wed, 13 Jan 2016 21:54:10 +0100,
> > Takashi Iwai wrote:
> >>
> >> OK, then this might be a possible race at the current snd_timer_stop()
> >> implementation.  There is no sync action there, so the ISR might be
> >> still alive after snd_timer_close() call.  Or might be another race.
> >> This pattern looks a bit different, as it's involved with hrtimer.
> >>
> >> I'll take a look at it tomorrow.
> >
> > I've audited the code today, but the open window doesn't look like
> > what I expected.  I found only some possible cases with slave timer
> > instances.
> >
> > In anyway, below is a test fix patch.  Since I couldn't reproduce the
> > issue on my local machines, it's hard to say whether this covers the
> > holes you fell.  Let's see...
> 
> 
> Hi Takashi,
> 
> I would be interested to understand why other people can't reproduce
> issues that I hit pretty reliably.
> I suspect that it can be due to .config. Please try with the following
> config values.

I guess rather other config, e.g. the kernel debug options.
I suppose you enabled KASAN and DEBUG_LIST.  What else?


> I also start qemu with "-soundhw all" arg.

OK, so you're testing with VM?  This makes easier to recheck.


Takashi