Re: INFO: rcu detected stall in corrupted (3)

[Thomas Gleixner]

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:ÂÂÂ 8c2ffd91 Linux 5.1-rc2
> > git tree:ÂÂÂÂÂÂ upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=15099d2b200000
> > kernel config:Â https://syzkaller.appspot.com/x/.config?x=8dcdce25ea72bedf
> > dashboard link: https://syzkaller.appspot.com/bug?extid=65cecdd27b726c261799
> > compiler:ÂÂÂÂÂÂ gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:ÂÂÂÂÂ https://syzkaller.appspot.com/x/repro.syz?x=17d3c67d200000
> > C reproducer:ÂÂ 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