Re: [syzbot] [serial?] KASAN: use-after-free Read in gsm_cleanup_mux

[syzbot]

syzbot has bisected this issue to:

commit 01aecd917114577c423f07cec0d186ad007d76fc
Author: Daniel Starke <daniel.starke@xxxxxxxxxxx>
Date:   Fri Jul 1 06:16:45 2022 +0000

    tty: n_gsm: fix tty registration before control channel open

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10d431ea680000
start commit:   a4412fdd49dc error-injection: Add prompt for function erro..
git tree:       upstream
final oops:     https://syzkaller.appspot.com/x/report.txt?x=12d431ea680000
console output: https://syzkaller.appspot.com/x/log.txt?x=14d431ea680000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cc4b2e0a8e8a8366
dashboard link: https://syzkaller.appspot.com/bug?extid=893c55305230e719a203
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12b1ca83880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1023c5e3880000

Reported-by: syzbot+893c55305230e719a203@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 01aecd917114 ("tty: n_gsm: fix tty registration before control channel open")

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