On Mon, 06 Jun 2016 18:29:25 +0200,
Dmitry Vyukov wrote:
>
> On Mon, Jun 6, 2016 at 4:11 PM, Takashi Iwai <tiwai@xxxxxxx> wrote:
> > On Sat, 04 Jun 2016 20:27:50 +0200,
> > Dmitry Vyukov wrote:
> >>
> >> On Sat, Jun 4, 2016 at 8:00 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
> >> > Hello,
> >> >
> >> > The following program triggers use-after-free:
> >>
> >> Forget to mention that you need to run it in a tight parallel loop. It
> >> takes around 5 minutes to reproduce for me.
> >
> > Hmm, this again is a bug that is difficult to trigger... At least, I
> > couldn't reproduce locally. How many processes are you running with
> > stress program?
>
> I use a VM with 4 cores and use 20 parallel test processes.
>
> > It seems that there is nothing more than opening /dev/audio and does
> > some mmap in the job. Is there any other relevant thing there?
>
>
> I think poll with timeout is related. It is poll who sets hrtimer, right?
If it's about snd-dummy driver, hrtimer is created at open, and
started/stopped at PCM trigger, and removed at close.
Is there any good way to decode which syscalls are executed in the
test code?
Takashi
> > Also, this assumes that the first sound card is Dummy driver, right?
> > Check /proc/asound/cards.
>
> # cat /proc/asound/cards
> 0 [Dummy ]: Dummy - Dummy
> Dummy 1
> 1 [Loopback ]: Loopback - Loopback
> Loopback 1
> 2 [VirMIDI ]: VirMIDI - VirMIDI
> Virtual MIDI Card 1
> 3 [pcsp ]: PC-Speaker - pcsp
> Internal PC-Speaker at port 0x61
> 4 [Intel ]: HDA-Intel - HDA Intel
> HDA Intel at 0xfebf0000 irq 24
>
>
>
> > If it's about snd-dummy driver, one blind shot would be a patch like
> > below. But even if it would fix, it doesn't explain why it's
> > triggered in that way...
> >
> >
> > thanks,
> >
> > Takashi
> >
> > ---
> > diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c
> > index c0f8f613f1f1..172dacd925f5 100644
> > --- a/sound/drivers/dummy.c
> > +++ b/sound/drivers/dummy.c
> > @@ -420,6 +420,7 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream)
> >
> > static inline void dummy_hrtimer_sync(struct dummy_hrtimer_pcm *dpcm)
> > {
> > + hrtimer_cancel(&dpcm->timer);
> > tasklet_kill(&dpcm->tasklet);
> > }
> >
>
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