general protection fault, probably for non-canonical address 0xdffffc000000000c: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000060-0x0000000000000067]
CPU: 0 PID: 24028 Comm: syz-executor.0 Not tainted 5.8.0-rc7-next-20200731-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:cdev_del+0x22/0x90 fs/char_dev.c:596
Code: b5 0f 1f 80 00 00 00 00 55 48 89 fd 48 83 ec 08 e8 03 fb b3 ff 48 8d 7d 64 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 4f 48
RSP: 0018:ffffc90008ac7ce8 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: ffff8880a1be2000 RCX: ffffffff83eb193f
RDX: 000000000000000c RSI: ffffffff81c0450d RDI: 0000000000000064
RBP: 0000000000000000 R08: 0000000000000001 R09: ffffffff8c66daef
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880a1be2008
R13: ffff8880a14f7008 R14: ffff888098657028 R15: ffff88809d43c650
FS:  0000000000f9a940(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2fa24000 CR3: 00000000a76c8000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 tty_unregister_device drivers/tty/tty_io.c:3193 [inline]
 tty_unregister_device+0x112/0x1b0 drivers/tty/tty_io.c:3188
 gsmld_detach_gsm drivers/tty/n_gsm.c:2411 [inline]
 gsmld_close+0xaa/0x260 drivers/tty/n_gsm.c:2480
 tty_ldisc_close+0x110/0x190 drivers/tty/tty_ldisc.c:489
 tty_ldisc_kill+0x94/0x150 drivers/tty/tty_ldisc.c:637
 tty_ldisc_release+0xe1/0x2a0 drivers/tty/tty_ldisc.c:809
 tty_release_struct+0x20/0xe0 drivers/tty/tty_io.c:1614
 tty_release+0xc67/0xf60 drivers/tty/tty_io.c:1785
 __fput+0x285/0x920 fs/file_table.c:281
 task_work_run+0xdd/0x190 kernel/task_work.c:135
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:139 [inline]
 exit_to_user_mode_prepare+0x195/0x1c0 kernel/entry/common.c:166
 syscall_exit_to_user_mode+0x59/0x2b0 kernel/entry/common.c:241
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4167f1
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 1b 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007ffec56ef600 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000006 RCX: 00000000004167f1
RDX: 0000000000000000 RSI: 000000000000155c RDI: 0000000000000005
RBP: 0000000000000001 R08: 00000000a794d55f R09: 0000000000000000
R10: 00007ffec56ef6f0 R11: 0000000000000293 R12: 000000000078c900
R13: 000000000078c900 R14: ffffffffffffffff R15: 000000000078bf0c
Modules linked in:
---[ end trace c040b2e60b907c9d ]---
RIP: 0010:cdev_del+0x22/0x90 fs/char_dev.c:596
Code: b5 0f 1f 80 00 00 00 00 55 48 89 fd 48 83 ec 08 e8 03 fb b3 ff 48 8d 7d 64 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 4f 48
RSP: 0018:ffffc90008ac7ce8 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: ffff8880a1be2000 RCX: ffffffff83eb193f
RDX: 000000000000000c RSI: ffffffff81c0450d RDI: 0000000000000064
RBP: 0000000000000000 R08: 0000000000000001 R09: ffffffff8c66daef
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880a1be2008
R13: ffff8880a14f7008 R14: ffff888098657028 R15: ffff88809d43c650
FS:  0000000000f9a940(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe794431028 CR3: 00000000a76c8000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400