On Mon, Jan 8, 2018 at 2:15 PM, Takashi Iwai tiwai@suse.de wrote:
On Sun, 07 Jan 2018 12:30:53 +0100, Dmitry Vyukov wrote:
On Thu, Jan 4, 2018 at 6:03 PM, Takashi Iwai tiwai@suse.de wrote:
On Thu, 04 Jan 2018 15:17:23 +0100, Takashi Iwai wrote:
On Thu, 04 Jan 2018 15:01:06 +0100, Dmitry Vyukov wrote:
On Thu, Jan 4, 2018 at 1:57 PM, Takashi Iwai tiwai@suse.de wrote:
On Thu, 04 Jan 2018 13:08:45 +0100, Dmitry Vyukov wrote: > > On Thu, Jan 4, 2018 at 1:03 PM, syzbot > syzbot+387f48da65cb522abfe8@syzkaller.appspotmail.com wrote: > > Hello, > > > > syzkaller hit the following crash on > > 30a7acd573899fd8b8ac39236eff6468b195ac7d > > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master > > compiler: gcc (GCC) 7.1.1 20170620 > > .config is attached > > Raw console output is attached. > > Unfortunately, I don't have any reproducer for this bug yet. > > > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+387f48da65cb522abfe8@syzkaller.appspotmail.com > > It will help syzbot understand when the bug is fixed. See footer for > > details. > > If you forward the report, please keep this part and the footer. > > This looks ALSA-related. +ALSA maintainers.
Not sure exactly what triggers it. It's the simple memcpy(), and I don't know where RCU is involved in that code path.
BTW, other two suspicious RCU usage reports are actually stopped at the second WARN_ON() after the RCU message, and the second WARN_ON() is independent from RCU; it's the known spurious WARN_ON() and was already removed in the sound git tree.
Hi Takashi,
Another similar one just popped up:
https://groups.google.com/forum/#!topic/syzkaller-bugs/X3d6-PIrJM0
This looks like mulaw_decode enters an infinite loop, or at least doing very large amount of computations without a resched, e.g. (uint64_t)-1 number of iterations of something along these lines.
OK, that makes sense.
My rough guess is that it's the misconfigured aloop device by concurrent setup. The aloop device allows to restrict the parameters of the other side of the connection, and something bad may happen there if both sides are updated concurrently.
We've seen segfault by memset() at loopback_preapre() in sound/drivers/aloop.c by syzbot+3902b5220e8ca27889ca, too, which indicates also the wrongly setup parameters that overflows the allocated buffer.
Below two patches may possibly plug the holes, but I'm not entirely sure whether that's the exact culprit. Could you put them into syzbot to watch whether they have any influence?
Hi Takashi,
I've gave an answer to this here: https://groups.google.com/d/msg/syzkaller-bugs/7ucgCkAJKSk/skZjgavRAQAJ
OK, noted.
In anyway, they are obvious bugs to be fixed, so I'm going to queue to my tree.
The options are:
- You can ask syzbot to test the patch separately. This requires a
reproducer, but there is this bug which has a reproducer and seems to have the same root cause: https://groups.google.com/d/msg/syzkaller-bugs/KrPUlf-nm5g/Vk0xEq-HAAAJ
Ah, I didn't know that each bot can test patches individually.
- You can reproduce it with the reproducer from here:
https://groups.google.com/d/msg/syzkaller-bugs/KrPUlf-nm5g/Vk0xEq-HAAAJ and then test the patch as extensively as needed.
Yes, I could test and find the culprit with the given reproducer.
- If you have some confidence that the patch fixes the problem, then
mark the commit with the tag: Reported-by: syzbot+387f48da65cb522abfe8@syzkaller.appspotmail.com then syzbot will notify if this still happens after the commit reaches tested trees.
Some have been already tagged with reported-by. Some are mostly irrelevant but casually found during the debug session for the bugs syzkaller spotted.
I think this is fixed with:
#syz fix: ALSA: pcm: Abort properly at pending signal in OSS read/write loops