| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <s5hr3bmsoez.wl-tiwai@suse.de>
Date: Fri, 24 Jun 2016 15:32:20 +0200
From: Takashi Iwai <tiwai@...e.de>
To: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
LKML <linux-kernel@...r.kernel.org>,
Sasha Levin <sasha.levin@...cle.com>,
Alexander Potapenko <glider@...gle.com>,
Kostya Serebryany <kcc@...gle.com>,
syzkaller <syzkaller@...glegroups.com>
Subject: Re: sound: use-after-free in hrtimer_cancel
On Tue, 21 Jun 2016 20:26:48 +0200,
Dmitry Vyukov wrote:
>
> On Mon, Jun 6, 2016 at 4:11 PM, Takashi Iwai <tiwai@...e.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@...gle.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?
> >
> > 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?
> >
> > Also, this assumes that the first sound card is Dummy driver, right?
> > Check /proc/asound/cards.
> >
> > 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);
> > }
>
>
> Yes, this seems to fix it. I've stressed it for an hour with several
> reproducers. If I am not mistaken, it also makes test cases run 15%
> faster.
Interesting. Possibly because it now syncs properly before other
restart of stream or such...
> Please mail a patch.
OK, below is the formal patch.
Let me know if I can give your tested-by tag.
thanks,
Takashi
-- 8< --
From: Takashi Iwai <tiwai@...e.de>
Subject: [PATCH] ALSA: dummy: Fix a use-after-free at closing
syzkaller fuzzer spotted a potential use-after-free case in snd-dummy
driver when hrtimer is used as backend:
> ==================================================================
> BUG: KASAN: use-after-free in rb_erase+0x1b17/0x2010 at addr ffff88005e5b6f68
> Read of size 8 by task syz-executor/8984
> =============================================================================
> BUG kmalloc-192 (Not tainted): kasan: bad access detected
> -----------------------------------------------------------------------------
>
> Disabling lock debugging due to kernel taint
> INFO: Allocated in 0xbbbbbbbbbbbbbbbb age=18446705582212484632
> ....
> [< none >] dummy_hrtimer_create+0x49/0x1a0 sound/drivers/dummy.c:464
> ....
> INFO: Freed in 0xfffd8e09 age=18446705496313138713 cpu=2164287125 pid=-1
> [< none >] dummy_hrtimer_free+0x68/0x80 sound/drivers/dummy.c:481
> ....
> Call Trace:
> [<ffffffff8179e59e>] __asan_report_load8_noabort+0x3e/0x40 mm/kasan/report.c:333
> [< inline >] rb_set_parent include/linux/rbtree_augmented.h:111
> [< inline >] __rb_erase_augmented include/linux/rbtree_augmented.h:218
> [<ffffffff82ca5787>] rb_erase+0x1b17/0x2010 lib/rbtree.c:427
> [<ffffffff82cb02e8>] timerqueue_del+0x78/0x170 lib/timerqueue.c:86
> [<ffffffff814d0c80>] __remove_hrtimer+0x90/0x220 kernel/time/hrtimer.c:903
> [< inline >] remove_hrtimer kernel/time/hrtimer.c:945
> [<ffffffff814d23da>] hrtimer_try_to_cancel+0x22a/0x570 kernel/time/hrtimer.c:1046
> [<ffffffff814d2742>] hrtimer_cancel+0x22/0x40 kernel/time/hrtimer.c:1066
> [<ffffffff85420531>] dummy_hrtimer_stop+0x91/0xb0 sound/drivers/dummy.c:417
> [<ffffffff854228bf>] dummy_pcm_trigger+0x17f/0x1e0 sound/drivers/dummy.c:507
> [<ffffffff85392170>] snd_pcm_do_stop+0x160/0x1b0 sound/core/pcm_native.c:1106
> [<ffffffff85391b26>] snd_pcm_action_single+0x76/0x120 sound/core/pcm_native.c:956
> [<ffffffff85391e01>] snd_pcm_action+0x231/0x290 sound/core/pcm_native.c:974
> [< inline >] snd_pcm_stop sound/core/pcm_native.c:1139
> [<ffffffff8539754d>] snd_pcm_drop+0x12d/0x1d0 sound/core/pcm_native.c:1784
> [<ffffffff8539d3be>] snd_pcm_common_ioctl1+0xfae/0x2150 sound/core/pcm_native.c:2805
> [<ffffffff8539ee91>] snd_pcm_capture_ioctl1+0x2a1/0x5e0 sound/core/pcm_native.c:2976
> [<ffffffff8539f2ec>] snd_pcm_kernel_ioctl+0x11c/0x160 sound/core/pcm_native.c:3020
> [<ffffffff853d9a44>] snd_pcm_oss_sync+0x3a4/0xa30 sound/core/oss/pcm_oss.c:1693
> [<ffffffff853da27d>] snd_pcm_oss_release+0x1ad/0x280 sound/core/oss/pcm_oss.c:2483
> .....
A workaround is to call hrtimer_cancel() in dummy_hrtimer_sync() which
is called certainly before other blocking ops.
Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
sound/drivers/dummy.c | 1 +
1 file changed, 1 insertion(+)
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);
}
--
2.9.0
Powered by blists - more mailing lists