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Date: Fri, 15 Jan 2016 12:00:05 +0100
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From: Takashi Iwai <tiwai@suse.de>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: alsa-devel@alsa-project.org, Jie Yang <yang.jie@intel.com>,
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        Kostya Serebryany <kcc@google.com>,
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        Sasha Levin <sasha.levin@oracle.com>
Subject: Re: sound: use-after-free in snd_timer_interrupt
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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