======================================
| [  160.202508] ------------[ cut here ]------------
| [  160.202923] refcount_t: underflow; use-after-free.
| [  160.203362] WARNING: CPU: 3 PID: 10 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
| [  160.204033] Modules linked in: act_gact cls_flower vxlan ip6_udp_tunnel udp_tunnel bridge stp llc sch_ingress vrf veth
[  160.205510] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  160.206444] Workqueue: netns cleanup_net
[  160.206772] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[ 160.207212] Code: 0b 90 90 c3 cc cc cc cc 80 3d a1 b9 66 01 00 0f 85 75 ff ff ff c6 05 94 b9 66 01 01 90 48 c7 c7 c8 70 0f 87 e8 71 92 b4 ff 90 <0f> 0b 90 90 c3 cc cc cc cc 80 3d 74 b9 66 01 00 0f 85 4a ff ff ff
All code
========
   0:	0b 90 90 c3 cc cc    	or     -0x33333c70(%rax),%edx
   6:	cc                   	int3
   7:	cc                   	int3
   8:	80 3d a1 b9 66 01 00 	cmpb   $0x0,0x166b9a1(%rip)        # 0x166b9b0
   f:	0f 85 75 ff ff ff    	jne    0xffffffffffffff8a
  15:	c6 05 94 b9 66 01 01 	movb   $0x1,0x166b994(%rip)        # 0x166b9b0
  1c:	90                   	nop
  1d:	48 c7 c7 c8 70 0f 87 	mov    $0xffffffff870f70c8,%rdi
  24:	e8 71 92 b4 ff       	call   0xffffffffffb4929a
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	c3                   	ret
  2f:	cc                   	int3
  30:	cc                   	int3
  31:	cc                   	int3
  32:	cc                   	int3
  33:	80 3d 74 b9 66 01 00 	cmpb   $0x0,0x166b974(%rip)        # 0x166b9ae
  3a:	0f 85 4a ff ff ff    	jne    0xffffffffffffff8a

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	c3                   	ret
   5:	cc                   	int3
   6:	cc                   	int3
   7:	cc                   	int3
   8:	cc                   	int3
   9:	80 3d 74 b9 66 01 00 	cmpb   $0x0,0x166b974(%rip)        # 0x166b984
  10:	0f 85 4a ff ff ff    	jne    0xffffffffffffff60
[  160.208702] RSP: 0018:ffffc05e0005bd78 EFLAGS: 00010286
[  160.209148] RAX: 0000000000000000 RBX: ffff9ce381d3a000 RCX: 00000000ffffdfff
[  160.209728] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  160.210318] RBP: ffff9ce381d3a5f8 R08: ffffffff87564508 R09: 00000000ffffdfff
[  160.210899] R10: ffffffff87484520 R11: ffffffff87534520 R12: ffff9ce381d3a000
[  160.211490] R13: ffffc05e0005be08 R14: ffff9ce381d3ab60 R15: ffff9ce385590050
[  160.212068] FS:  0000000000000000(0000) GS:ffff9ce3bed80000(0000) knlGS:0000000000000000
[  160.212744] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  160.213220] CR2: 00007fc7c6d7a270 CR3: 000000000594e003 CR4: 00000000001706f0
[  160.213799] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  160.214374] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  160.214942] Call Trace:
[  160.215160]  <TASK>
[  160.215343] ? __warn (kernel/panic.c:677) 
[  160.215622] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  160.216010] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  160.216334] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  160.216631] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  160.216957] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  160.217325] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  160.217710] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  160.218099] br_sysfs_delbr (net/bridge/br_sysfs_br.c:1086) bridge
[  160.218543] br_dev_delete (net/bridge/br_if.c:396) bridge
[  160.218919] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  160.219371] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  160.219682] ? process_one_work (kernel/workqueue.c:2606) 
[  160.220029] process_one_work (kernel/workqueue.c:2638) 
[  160.220383] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  160.220695] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  160.221051] kthread (kernel/kthread.c:388) 
[  160.221329] ? __pfx_kthread (kernel/kthread.c:341) 
[  160.221646] ret_from_fork (arch/x86/kernel/process.c:153) 
[  160.221948] ? __pfx_kthread (kernel/kthread.c:341) 
[  160.222273] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  160.226238] ------------[ cut here ]------------
| [  160.226611] sysfs group 'bridge' not found for kobject 'br2'
| [  160.227108] WARNING: CPU: 3 PID: 10 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  160.227765] Modules linked in: act_gact cls_flower vxlan ip6_udp_tunnel udp_tunnel bridge stp llc sch_ingress vrf veth
[  160.229347] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  160.230265] Workqueue: netns cleanup_net
[  160.230596] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 160.230997] Code: 48 89 ef 5d 41 5c e9 0a ae ff ff 48 89 ef e8 a2 9b ff ff eb d1 90 49 8b 14 24 48 8b 33 48 c7 c7 b0 06 0f 87 e8 fc b0 c5 ff 90 <0f> 0b 90 90 5b 5d 41 5c c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00
All code
========
   0:	48 89 ef             	mov    %rbp,%rdi
   3:	5d                   	pop    %rbp
   4:	41 5c                	pop    %r12
   6:	e9 0a ae ff ff       	jmp    0xffffffffffffae15
   b:	48 89 ef             	mov    %rbp,%rdi
   e:	e8 a2 9b ff ff       	call   0xffffffffffff9bb5
  13:	eb d1                	jmp    0xffffffffffffffe6
  15:	90                   	nop
  16:	49 8b 14 24          	mov    (%r12),%rdx
  1a:	48 8b 33             	mov    (%rbx),%rsi
  1d:	48 c7 c7 b0 06 0f 87 	mov    $0xffffffff870f06b0,%rdi
  24:	e8 fc b0 c5 ff       	call   0xffffffffffc5b125
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	5b                   	pop    %rbx
  2f:	5d                   	pop    %rbp
  30:	41 5c                	pop    %r12
  32:	c3                   	ret
  33:	cc                   	int3
  34:	cc                   	int3
  35:	cc                   	int3
  36:	cc                   	int3
  37:	66                   	data16
  38:	66                   	data16
  39:	2e                   	cs
  3a:	0f                   	.byte 0xf
  3b:	1f                   	(bad)
  3c:	84 00                	test   %al,(%rax)
	...

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	5b                   	pop    %rbx
   5:	5d                   	pop    %rbp
   6:	41 5c                	pop    %r12
   8:	c3                   	ret
   9:	cc                   	int3
   a:	cc                   	int3
   b:	cc                   	int3
   c:	cc                   	int3
   d:	66                   	data16
   e:	66                   	data16
   f:	2e                   	cs
  10:	0f                   	.byte 0xf
  11:	1f                   	(bad)
  12:	84 00                	test   %al,(%rax)
	...
[  160.232590] RSP: 0018:ffffc05e0005bd70 EFLAGS: 00010286
[  160.233016] RAX: 0000000000000000 RBX: ffffffffc02b5c60 RCX: 00000000ffffdfff
[  160.233597] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  160.234183] RBP: 0000000000000000 R08: ffffffff87564508 R09: 00000000ffffdfff
[  160.234756] R10: ffffffff87484520 R11: ffffffff87534520 R12: ffff9ce381d3a5f8
[  160.235349] R13: ffffc05e0005be08 R14: ffff9ce381d3ab60 R15: ffff9ce385590050
[  160.235923] FS:  0000000000000000(0000) GS:ffff9ce3bed80000(0000) knlGS:0000000000000000
[  160.236576] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  160.237049] CR2: 00007fc7c6d7a270 CR3: 000000000594e003 CR4: 00000000001706f0
[  160.237641] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  160.238224] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  160.238798] Call Trace:
[  160.239008]  <TASK>
[  160.239205] ? __warn (kernel/panic.c:677) 
[  160.239480] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  160.239828] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  160.240153] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  160.240448] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  160.240770] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  160.241131] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  160.241484] br_dev_delete (net/bridge/br_if.c:396) bridge
[  160.241883] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  160.242341] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  160.242658] ? process_one_work (kernel/workqueue.c:2606) 
[  160.243007] process_one_work (kernel/workqueue.c:2638) 
[  160.243357] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  160.243671] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  160.244025] kthread (kernel/kthread.c:388) 
[  160.244296] ? __pfx_kthread (kernel/kthread.c:341) 
[  160.244599] ret_from_fork (arch/x86/kernel/process.c:153) 
[  160.244899] ? __pfx_kthread (kernel/kthread.c:341) 
[  160.245220] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  160.342293] ------------[ cut here ]------------
| [  160.342581] sysfs group 'bridge' not found for kobject 'br2'
| [  160.342910] WARNING: CPU: 3 PID: 10 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  160.343371] Modules linked in: act_gact cls_flower vxlan ip6_udp_tunnel udp_tunnel bridge stp llc sch_ingress vrf veth
[  160.344424] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  160.345067] Workqueue: netns cleanup_net
[  160.345317] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 160.345589] Code: 48 89 ef 5d 41 5c e9 0a ae ff ff 48 89 ef e8 a2 9b ff ff eb d1 90 49 8b 14 24 48 8b 33 48 c7 c7 b0 06 0f 87 e8 fc b0 c5 ff 90 <0f> 0b 90 90 5b 5d 41 5c c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00
All code
========
   0:	48 89 ef             	mov    %rbp,%rdi
   3:	5d                   	pop    %rbp
   4:	41 5c                	pop    %r12
   6:	e9 0a ae ff ff       	jmp    0xffffffffffffae15
   b:	48 89 ef             	mov    %rbp,%rdi
   e:	e8 a2 9b ff ff       	call   0xffffffffffff9bb5
  13:	eb d1                	jmp    0xffffffffffffffe6
  15:	90                   	nop
  16:	49 8b 14 24          	mov    (%r12),%rdx
  1a:	48 8b 33             	mov    (%rbx),%rsi
  1d:	48 c7 c7 b0 06 0f 87 	mov    $0xffffffff870f06b0,%rdi
  24:	e8 fc b0 c5 ff       	call   0xffffffffffc5b125
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	5b                   	pop    %rbx
  2f:	5d                   	pop    %rbp
  30:	41 5c                	pop    %r12
  32:	c3                   	ret
  33:	cc                   	int3
  34:	cc                   	int3
  35:	cc                   	int3
  36:	cc                   	int3
  37:	66                   	data16
  38:	66                   	data16
  39:	2e                   	cs
  3a:	0f                   	.byte 0xf
  3b:	1f                   	(bad)
  3c:	84 00                	test   %al,(%rax)
	...

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	5b                   	pop    %rbx
   5:	5d                   	pop    %rbp
   6:	41 5c                	pop    %r12
   8:	c3                   	ret
   9:	cc                   	int3
   a:	cc                   	int3
   b:	cc                   	int3
   c:	cc                   	int3
   d:	66                   	data16
   e:	66                   	data16
   f:	2e                   	cs
  10:	0f                   	.byte 0xf
  11:	1f                   	(bad)
  12:	84 00                	test   %al,(%rax)
	...
[  160.346609] RSP: 0018:ffffc05e0005bd70 EFLAGS: 00010286
[  160.346896] RAX: 0000000000000000 RBX: ffffffffc02b5c60 RCX: 00000000ffffdfff
[  160.347289] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  160.347705] RBP: 0000000000000000 R08: ffffffff87564508 R09: 00000000ffffdfff
[  160.348105] R10: ffffffff87484520 R11: ffffffff87534520 R12: ffff9ce38190c5f8
[  160.348500] R13: ffffc05e0005be08 R14: ffff9ce38190cb60 R15: ffffffff88a13dd0
[  160.348911] FS:  0000000000000000(0000) GS:ffff9ce3bed80000(0000) knlGS:0000000000000000
[  160.349362] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  160.349674] CR2: 00007fc7c6d7a270 CR3: 000000002a64c004 CR4: 00000000001706f0
[  160.350090] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  160.350472] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  160.350853] Call Trace:
[  160.350999]  <TASK>
[  160.351143] ? __warn (kernel/panic.c:677) 
[  160.351331] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  160.351560] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  160.351775] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  160.351971] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  160.352201] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  160.352465] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  160.352711] br_dev_delete (net/bridge/br_if.c:396) bridge
[  160.352988] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  160.353303] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  160.353508] ? process_one_work (kernel/workqueue.c:2606) 
[  160.353756] process_one_work (kernel/workqueue.c:2638) 
[  160.353991] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  160.354213] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  160.354451] kthread (kernel/kthread.c:388) 
[  160.354630] ? __pfx_kthread (kernel/kthread.c:341) 
[  160.354838] ret_from_fork (arch/x86/kernel/process.c:153) 
[  160.355052] ? __pfx_kthread (kernel/kthread.c:341) 


Finger prints:
refcount_warn_saturate:br_sysfs_delbr:br_dev_delete:br_net_exit_batch_rtnl
sysfs_remove_group:br_dev_delete:br_net_exit_batch_rtnl:cleanup_net
sysfs_remove_group:br_dev_delete:br_net_exit_batch_rtnl:cleanup_net