linux-kernel - Re: INFO: rcu detected stall in sys

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Message-ID: <a5478450-f975-228f-1ca6-886a45b654a1@I-love.SAKURA.ne.jp>
Date:   Wed, 19 Dec 2018 19:11:58 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     syzbot <syzbot+bcad772bbc241b4c6147@...kaller.appspotmail.com>,
        syzkaller-bugs@...glegroups.com, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     jmorris@...ei.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, serge@...lyn.com
Subject: Re: INFO: rcu detected stall in sys_sendfile64

On 2018/12/19 18:27, syzbot wrote:
> HEAD commit:    ddfbab46539f Merge tag 'scsi-fixes' of git://git.kernel.or..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15b87fa3400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=861a3573f4e78ba1
> dashboard link: https://syzkaller.appspot.com/bug?extid=bcad772bbc241b4c6147
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13912ccd400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=145781db400000

This is not a LSM problem, for the reproducer is calling
sched_setattr(SCHED_DEADLINE) with very large values.

  sched_setattr(0, {size=0, sched_policy=0x6 /* SCHED_??? */, sched_flags=0, sched_nice=0, sched_priority=0, sched_runtime=2251799813724439, sched_deadline=4611686018427453437, sched_period=0}, 0) = 0

I think that this problem is nothing but an insane sched_setattr() parameter.

#syz invalid