Re: general protection fault in percpu_ref_exit

[syzbot]

syzbot has bisected this issue to:

commit 2b0d3d3e4fcfb19d10f9a82910b8f0f05c56ee3e
Author: Ming Lei <ming.lei@xxxxxxxxxx>
Date:   Thu Oct 1 15:48:41 2020 +0000

    percpu_ref: reduce memory footprint of percpu_ref in fast path

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=126930d0500000
start commit:   8b787da7 Add linux-next specific files for 20201007
git tree:       linux-next
final oops:     https://syzkaller.appspot.com/x/report.txt?x=116930d0500000
console output: https://syzkaller.appspot.com/x/log.txt?x=166930d0500000
kernel config:  https://syzkaller.appspot.com/x/.config?x=aac055e9c8fbd2b8
dashboard link: https://syzkaller.appspot.com/bug?extid=fd15ff734dace9e16437
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=119a0568500000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=106c0a8b900000

Reported-by: syzbot+fd15ff734dace9e16437@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 2b0d3d3e4fcf ("percpu_ref: reduce memory footprint of percpu_ref in fast path")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection