linux-kernel - Re: INFO: rcu detected stall in corrupted (3)

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Date:   Sat, 30 Mar 2019 08:46:42 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
cc:     syzbot <syzbot+65cecdd27b726c261799@...kaller.appspotmail.com>,
        syzkaller-bugs@...glegroups.com, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>, mingo@...hat.com,
        x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>
Subject: Re: INFO: rcu detected stall in corrupted (3)

On Sat, 30 Mar 2019, Tetsuo Handa wrote:

> On 2019/03/30 7:34, syzbot wrote:
> > Hello,
> > 
> > syzbot found the following crash on:
> > 
> > HEAD commit:    8c2ffd91 Linux 5.1-rc2
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=15099d2b200000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=8dcdce25ea72bedf
> > dashboard link: https://syzkaller.appspot.com/bug?extid=65cecdd27b726c261799
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17d3c67d200000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11d4f317200000
> > 
> > Bisection is inconclusive: the bug happens on the oldest tested release.
> 
> This reproducer does sched_setattr(SCHED_DEADLINE) with bogus value, as with
> a reproducer for "INFO: rcu detected stall in sys_sendfile64" did.
> 
> sched_setattr(0, {size=0, sched_policy=0x6 /* SCHED_DEADLINE */,
> sched_flags=0, sched_nice=0, sched_priority=0, sched_runtime=65535,
> sched_deadline=4611686018427453437, sched_period=0}, 0) = 0
>
> #syz invalid

Marking this invalid is not really the right thing to do. Bogus deadline
parameters should not cause RCU stalls. They either need to be rejected or
handled gracefully.

Thanks,

	tglx