Re: general protection fault in finish_task_switch (2)

[Peter Zijlstra]

On Tue, Aug 21, 2018 at 02:28:02PM -0700, syzbot wrote:
> syzbot has found a reproducer for the following crash on:
> 
> HEAD commit:    778a33959a8a Merge tag 'please-pull-noboot' of git://git.k..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14a5385a400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=214e4990bd49329f
> dashboard link: https://syzkaller.appspot.com/bug?extid=1f56df64bfb3c29dde6f
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> userspace arch: i386
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=13ffa561400000

FWIW the lack of whitespace between "repro:" and the URL makes it hard
to copy paste.

> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10023961400000


> RIP: 0010:__fire_sched_in_preempt_notifiers kernel/sched/core.c:2481

That repro thing does something dodgy with KVM, which then corrupts the
premption notifier thing. I'm sufficiently KVM clueless to not really
know where to start looking though..