syzbot has bisected this issue to:

commit a9ed4a6560b8562b7e2e2bed9527e88001f7b682 Author: Marc Zyngier maz@kernel.org Date: Wed Aug 19 16:12:17 2020 +0000

epoll: Keep a reference on files added to the check list

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=15e57751900000 start commit: 15bc20c6 Merge tag 'tty-5.9-rc3' of git://git.kernel.org/p.. git tree: upstream final oops: https://syzkaller.appspot.com/x/report.txt?x=17e57751900000 console output: https://syzkaller.appspot.com/x/log.txt?x=13e57751900000 kernel config: https://syzkaller.appspot.com/x/.config?x=978db74cb30aa994 dashboard link: https://syzkaller.appspot.com/bug?extid=e3cf8f93cf86936710db userspace arch: i386 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13236eb6900000

Reported-by: syzbot+e3cf8f93cf86936710db@syzkaller.appspotmail.com Fixes: a9ed4a6560b8 ("epoll: Keep a reference on files added to the check list")

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