BUG: unable to handle kernel NULL pointer dereference in fbcon_cursor

[syzbot]

syzbot has bisected this issue to:

commit ea40d7857d5250e5400f38c69ef9e17321e9c4a2
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Fri Oct 9 23:21:56 2020 +0000

    drm/vkms: fbdev emulation support

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=148e2748d00000
start commit:   b3a3cbde Add linux-next specific files for 20210115
git tree:       linux-next
final oops:     https://syzkaller.appspot.com/x/report.txt?x=168e2748d00000
console output: https://syzkaller.appspot.com/x/log.txt?x=128e2748d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6ea08dae6aab586f
dashboard link: https://syzkaller.appspot.com/bug?extid=b67aaae8d3a927f68d20
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15cd8fe0d00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17af5258d00000

Reported-by: syzbot+b67aaae8d3a927f68d20 at syzkaller.appspotmail.com
Fixes: ea40d7857d52 ("drm/vkms: fbdev emulation support")

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