kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 1 PID: 31231 Comm: syz-executor.5 Not tainted 4.14.273-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff88807e46a3c0 task.stack: ffff8880b4e30000
RIP: 0010:cdev_del+0x22/0x90 fs/char_dev.c:602
RSP: 0018:ffff8880b4e37ba0 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: ffff888238fd9700 RCX: ffffc900089f3000
RDX: 000000000000000c RSI: ffffffff8187ae5d RDI: 0000000000000064
RBP: 0000000000000000 R08: ffffffff8b9c7270 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888238fd9708
R13: ffff8882384ce4c8 R14: ffff8880b1a59300 R15: ffff8880abc24470
FS:  00007f7d90403700(0000) GS:ffff8880ba500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000056221dfd4160 CR3: 0000000096b2b000 CR4: 00000000003406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 tty_unregister_device drivers/tty/tty_io.c:3046 [inline]
 tty_unregister_device+0x101/0x1a0 drivers/tty/tty_io.c:3041
 gsmld_detach_gsm drivers/tty/n_gsm.c:2305 [inline]
 gsmld_close+0xaa/0x1f0 drivers/tty/n_gsm.c:2374
 tty_ldisc_close+0x8c/0xc0 drivers/tty/tty_ldisc.c:505
 tty_set_ldisc+0x1b3/0x5d0 drivers/tty/tty_ldisc.c:600
 tiocsetd drivers/tty/tty_io.c:2351 [inline]
 tty_ioctl+0xa2a/0x1430 drivers/tty/tty_io.c:2595
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x75a/0xff0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x7f7d91aaf049
RSP: 002b:00007f7d90403168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f7d91bc2030 RCX: 00007f7d91aaf049
RDX: 0000000020000640 RSI: 0000000000005423 RDI: 0000000000000003
RBP: 00007f7d91b0908d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fffa3c6babf R14: 00007f7d90403300 R15: 0000000000022000
Code: e5 44 f7 ff eb d2 0f 1f 00 55 48 89 fd 48 83 ec 08 e8 e3 93 cd 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 
RIP: cdev_del+0x22/0x90 fs/char_dev.c:602 RSP: ffff8880b4e37ba0
---[ end trace 82bae87aa45be7f9 ]---
----------------
Code disassembly (best guess):
   0:	e5 44                	in     $0x44,%eax
   2:	f7 ff                	idiv   %edi
   4:	eb d2                	jmp    0xffffffd8
   6:	0f 1f 00             	nopl   (%rax)
   9:	55                   	push   %rbp
   a:	48 89 fd             	mov    %rdi,%rbp
   d:	48 83 ec 08          	sub    $0x8,%rsp
  11:	e8 e3 93 cd ff       	callq  0xffcd93f9
  16:	48 8d 7d 64          	lea    0x64(%rbp),%rdi
  1a:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  21:	fc ff df
  24:	48 89 fa             	mov    %rdi,%rdx
  27:	48 c1 ea 03          	shr    $0x3,%rdx
* 2b:	0f b6 14 02          	movzbl (%rdx,%rax,1),%edx <-- trapping instruction
  2f:	48 89 f8             	mov    %rdi,%rax
  32:	83 e0 07             	and    $0x7,%eax
  35:	83 c0 03             	add    $0x3,%eax
  38:	38 d0                	cmp    %dl,%al
  3a:	7c 04                	jl     0x40
  3c:	84 d2                	test   %dl,%dl
  3e:	75 4f                	jne    0x8f