On Wed, Mar 20 2019, syzbot wrote:

> syzbot has bisected this bug to:
>
> commit dee160df820de41ff2f59a715643680822a0ab06
> Author: NeilBrown <neilb@suse.com>
> Date:   Mon Nov 5 01:30:47 2018 +0000
>
>      locks: use properly initialized file_lock when unlocking.

This commit did not make it to mainline.
It was replaced by

Commit d6367d624137 ("fs/locks: use properly initialized file_lock when unlocking.")

which added a call to locks_init_lock() in flock_make_lock().

NeilBrown

>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=13f39fd7200000
> start commit:   dee160df locks: use properly initialized file_lock when un..
> git tree:       linux-next
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=100b9fd7200000
> console output: https://syzkaller.appspot.com/x/log.txt?x=17f39fd7200000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=caa433e1c8778437
> dashboard link: https://syzkaller.appspot.com/bug?extid=83e12cf81d2c14842146
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15bd9447400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1121d82b400000
>
> Reported-by: syzbot+83e12cf81d2c14842146@syzkaller.appspotmail.com
> Fixes: dee160df ("locks: use properly initialized file_lock when  
> unlocking.")