On Mon, Jun 6, 2016 at 4:11 PM, Takashi Iwai tiwai@suse.de 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@google.com 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?
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);}