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Subject: Re: INFO: rcu detected stall in sys_kill
To:     Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
        Dmitry Vyukov <dvyukov@google.com>
Cc:     syzbot <syzbot+de8d933e7d153aa0c1bb@syzkaller.appspotmail.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Casey Schaufler <casey@schaufler-ca.com>
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From:   Casey Schaufler <casey@schaufler-ca.com>
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Date:   Wed, 8 Jan 2020 09:19:34 -0800
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On 1/8/2020 2:25 AM, Tetsuo Handa wrote:
> On 2020/01/08 15:20, Dmitry Vyukov wrote:
>> I temporarily re-enabled smack instance and it produced another 50
>> stalls all over the kernel, and now keeps spewing a dozen every hour.

Do I have to be using clang to test this? I'm setting up to work on this,=

and don't want to waste time using my current tool chain if the problem
is clang specific.

> Since we can get stall reports rather easily, can we try modifying
> kernel command line (e.g. lsm=3Dsmack) and/or kernel config (e.g. no ka=
san) ?
>
>> I've mailed 3 new samples, you can see them here:
>> https://syzkaller.appspot.com/bug?extid=3Dde8d933e7d153aa0c1bb
>>
>> The config is provided, command line args are here:
>> https://github.com/google/syzkaller/blob/master/dashboard/config/upstr=
eam-smack.cmdline
>> Some non-default sysctls that syzbot sets are here:
>> https://github.com/google/syzkaller/blob/master/dashboard/config/upstr=
eam.sysctl
>> Image can be downloaded from here:
>> https://github.com/google/syzkaller/blob/master/docs/syzbot.md#crash-d=
oes-not-reproduce
>> syzbot uses GCE VMs with 2 CPUs and 7.5GB memory, but this does not
>> look to be virtualization-related (?) so probably should reproduce in
>> qemu too.
> Is it possible to add instance for linux-next.git that uses these confi=
gs?
> If yes, we could try adding some debug printk() under CONFIG_DEBUG_AID_=
FOR_SYZBOT=3Dy .