RBP: 00007f670a4a31d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffefc3fa28f R14: 00007f670a4a3300 R15: 0000000000022000
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: 0 PID: 16635 Comm: syz-executor.4 Not tainted 4.14.275-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff88809542a600 task.stack: ffff8880a3d88000
RIP: 0010:cdev_del+0x22/0x90 fs/char_dev.c:602
RSP: 0018:ffff8880a3d8fca0 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: ffff8880b093a400 RCX: 0000000000000000
RDX: 000000000000000c RSI: ffff88809542ae88 RDI: 0000000000000064
RBP: 0000000000000000 R08: ffffffff8b9b68d0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880b093a408
R13: ffff8880af79a1c8 R14: ffff88809f5f8a00 R15: ffff888093c56218
FS:  00005555572bb400(0000) GS:ffff8880ba400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6f011ae558 CR3: 000000007bd4f000 CR4: 00000000003406f0
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_ldisc_kill drivers/tty/tty_ldisc.c:651 [inline]
 tty_ldisc_release+0xe8/0x400 drivers/tty/tty_ldisc.c:818
 tty_release_struct+0x20/0xe0 drivers/tty/tty_io.c:1603
 tty_release+0xb3f/0x10d0 drivers/tty/tty_io.c:1776
 __fput+0x25f/0x7a0 fs/file_table.c:210
 task_work_run+0x11f/0x190 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0x1ad/0x200 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
 do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x7f670bae0c8b
RSP: 002b:00007ffefc3fa2f0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000007 RCX: 00007f670bae0c8b
RDX: 0000000000000000 RSI: 0000001b30722960 RDI: 0000000000000006
RBP: 00007f670bc42960 R08: 0000000000000000 R09: 0000000064a32d66
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000137d3c
R13: 00007ffefc3fa3f0 R14: 00007ffefc3fa410 R15: 0000000000000032
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: ffff8880a3d8fca0
---[ end trace 9da2ad22b5bad4ab ]---
----------------
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