[syzbot] [dri?] kernel BUG in vmf_insert_pfn_prot (2)

[syzbot]

syzbot has bisected this issue to:

commit 45d9c8dde4cd8589f9180309ec60f0da2ce486e4
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Thu Aug 12 13:14:12 2021 +0000

    drm/vgem: use shmem helpers

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=126094df680000
start commit:   d2f51b3516da Merge tag 'rtc-6.7' of git://git.kernel.org/p..
git tree:       upstream
final oops:     https://syzkaller.appspot.com/x/report.txt?x=116094df680000
console output: https://syzkaller.appspot.com/x/log.txt?x=166094df680000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1ffa1cec3b40f3ce
dashboard link: https://syzkaller.appspot.com/bug?extid=398e17b61dab22cc56bc
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16344918e80000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=156bb2c0e80000

Reported-by: syzbot+398e17b61dab22cc56bc at syzkaller.appspotmail.com
Fixes: 45d9c8dde4cd ("drm/vgem: use shmem helpers")

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