======================================
| [    3.575968] ------------[ cut here ]------------
| [    3.576123] refcount_t: underflow; use-after-free.
| [    3.576185] WARNING: CPU: 3 PID: 253 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [    3.576261] Modules linked in: xt_tcpudp xt_conntrack nft_compat nf_tables x_tables nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 tun
[    3.576483] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[    3.576536] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[    3.576588] Code: 8d e8 18 ed b9 ff 90 0f 0b 90 90 c3 80 3d d9 ea ea 00 00 75 89 c6 05 d0 ea ea 00 01 90 48 c7 c7 78 de b1 8d e8 f5 ec b9 ff 90 <0f> 0b 90 90 c3 80 3d b4 ea ea 00 00 0f 85 62 ff ff ff c6 05 a7 ea
All code
========
   0:	8d                   	lea    (bad),%ebp
   1:	e8 18 ed b9 ff       	call   0xffffffffffb9ed1e
   6:	90                   	nop
   7:	0f 0b                	ud2
   9:	90                   	nop
   a:	90                   	nop
   b:	c3                   	ret
   c:	80 3d d9 ea ea 00 00 	cmpb   $0x0,0xeaead9(%rip)        # 0xeaeaec
  13:	75 89                	jne    0xffffffffffffff9e
  15:	c6 05 d0 ea ea 00 01 	movb   $0x1,0xeaead0(%rip)        # 0xeaeaec
  1c:	90                   	nop
  1d:	48 c7 c7 78 de b1 8d 	mov    $0xffffffff8db1de78,%rdi
  24:	e8 f5 ec b9 ff       	call   0xffffffffffb9ed1e
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	c3                   	ret
  2f:	80 3d b4 ea ea 00 00 	cmpb   $0x0,0xeaeab4(%rip)        # 0xeaeaea
  36:	0f 85 62 ff ff ff    	jne    0xffffffffffffff9e
  3c:	c6                   	.byte 0xc6
  3d:	05                   	.byte 0x5
  3e:	a7                   	cmpsl  %es:(%rdi),%ds:(%rsi)
  3f:	ea                   	(bad)

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	c3                   	ret
   5:	80 3d b4 ea ea 00 00 	cmpb   $0x0,0xeaeab4(%rip)        # 0xeaeac0
   c:	0f 85 62 ff ff ff    	jne    0xffffffffffffff74
  12:	c6                   	.byte 0xc6
  13:	05                   	.byte 0x5
  14:	a7                   	cmpsl  %es:(%rdi),%ds:(%rsi)
  15:	ea                   	(bad)
[    3.576724] RSP: 0018:ffffbff1c0597e50 EFLAGS: 00010286
[    3.576767] RAX: 0000000000000000 RBX: ffffbff1c0597e60 RCX: 00000000ffffdfff
[    3.576837] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[    3.576907] RBP: ffffbff1c0597968 R08: ffffffff8df56d28 R09: 00000000ffffdfff
[    3.576988] R10: ffffffff8de76d40 R11: ffffffff8df26d40 R12: dead000000000122
[    3.577050] R13: 00000000fffb797c R14: 0000000000000001 R15: ffff9c8ac1f50000
[    3.577128] FS:  000000003edd83c0(0000) GS:ffff9c8b70758000(0000) knlGS:0000000000000000
[    3.577195] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    3.577253] CR2: 00007f4dce970000 CR3: 000000000302a005 CR4: 0000000000772ef0
[    3.577317] PKRU: 55555554
[    3.577348] Call Trace:
[    3.577371]  <TASK>
[    3.577393]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[    3.577441]  ? __tun_detach (./include/linux/ptr_ring.h:680 drivers/net/tun.c:625) tun
[    3.577510] tun_chr_close (./include/net/sock.h:1990 drivers/net/tun.c:643 drivers/net/tun.c:3436) tun
[    3.577560]  __fput (fs/file_table.c:469)
[    3.577616]  __x64_sys_close (fs/open.c:1592 fs/open.c:1574 fs/open.c:1574)
[    3.577652]  do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)
[    3.577697]  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
[    3.577747] RIP: 0033:0x4901eb
[    3.577793] Code: 03 00 00 00 0f 05 48 3d 00 f0 ff ff 77 41 c3 48 83 ec 18 89 7c 24 0c e8 c3 78 04 00 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 89 44 24 0c e8 21 79 04 00 8b 44
All code
========
   0:	03 00                	add    (%rax),%eax
   2:	00 00                	add    %al,(%rax)
   4:	0f 05                	syscall
   6:	48 3d 00 f0 ff ff    	cmp    $0xfffffffffffff000,%rax
   c:	77 41                	ja     0x4f
   e:	c3                   	ret
   f:	48 83 ec 18          	sub    $0x18,%rsp
  13:	89 7c 24 0c          	mov    %edi,0xc(%rsp)
  17:	e8 c3 78 04 00       	call   0x478df
  1c:	8b 7c 24 0c          	mov    0xc(%rsp),%edi
  20:	41 89 c0             	mov    %eax,%r8d
  23:	b8 03 00 00 00       	mov    $0x3,%eax
  28:	0f 05                	syscall
  2a:*	48 3d 00 f0 ff ff    	cmp    $0xfffffffffffff000,%rax		<-- trapping instruction
  30:	77 35                	ja     0x67
  32:	44 89 c7             	mov    %r8d,%edi
  35:	89 44 24 0c          	mov    %eax,0xc(%rsp)
  39:	e8 21 79 04 00       	call   0x4795f
  3e:	8b                   	.byte 0x8b
  3f:	44                   	rex.R

Code starting with the faulting instruction
===========================================
   0:	48 3d 00 f0 ff ff    	cmp    $0xfffffffffffff000,%rax
   6:	77 35                	ja     0x3d
   8:	44 89 c7             	mov    %r8d,%edi
   b:	89 44 24 0c          	mov    %eax,0xc(%rsp)
   f:	e8 21 79 04 00       	call   0x47935
  14:	8b                   	.byte 0x8b
  15:	44                   	rex.R
[    3.577940] RSP: 002b:00007ffda545a340 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
[    3.578006] RAX: ffffffffffffffda RBX: 00007ffda545a858 RCX: 00000000004901eb
[    3.578070] RDX: 0000000000000002 RSI: 0000000000000002 RDI: 0000000000000006
[    3.578145] RBP: 00007ffda545a380 R08: 0000000000000000 R09: 0000000000000000
[    3.578229] R10: 000000003ede0100 R11: 0000000000000293 R12: 00007ffda545a818


Finger prints:
refcount_warn_saturate:netdev_run_todo:tun_chr_close:__fput:__x64_sys_close