[syzbot] kernel BUG in vmf_insert_pfn_prot

[syzbot]

syzbot suspects this issue was fixed by commit:

commit a5b44c4adb1699661d22e5152fb26885f30a2e4c
Author: Thomas Zimmermann <tzimmermann at suse.de>
Date:   Mon Mar 20 15:07:44 2023 +0000

    drm/fbdev-generic: Always use shadow buffering

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1025ee07280000
start commit:   0326074ff465 Merge tag 'net-next-6.1' of git://git.kernel...
git tree:       upstream
kernel config:  https://syzkaller.appspot.com/x/.config?x=d323d85b1f8a4ed7
dashboard link: https://syzkaller.appspot.com/bug?extid=2d4f8693f438d2bd4bdb
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14fd1182880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17567514880000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: drm/fbdev-generic: Always use shadow buffering

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