Re: BUG: unable to handle kernel NULL pointer dereference in mem16_serial_out

[syzbot]

syzbot has bisected this bug to:

commit bd94c4077a0b2ecc35562c294f80f3659ecd8499
Author: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Date:   Wed Oct 28 03:46:05 2015 +0000

    serial: support 16-bit register interface for console

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=13723196e00000
start commit:   e42617b8 Linux 5.5-rc1
git tree:       upstream
final crash:    https://syzkaller.appspot.com/x/report.txt?x=10f23196e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=17723196e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3754e2c78c1adb82
dashboard link: https://syzkaller.appspot.com/bug?extid=92f32d4e21fb246d31a2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=136f7e41e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=112b7c82e00000

Reported-by: syzbot+92f32d4e21fb246d31a2@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: bd94c4077a0b ("serial: support 16-bit register interface for  
console")

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