======================================
| [  862.226227] ------------[ cut here ]------------
| [  862.226626] refcount_t: underflow; use-after-free.
| [  862.227068] WARNING: CPU: 2 PID: 11 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
| [  862.227734] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel bridge stp llc act_gact cls_flower sch_ingress 8021q ip6_gre ip6_tunnel tunnel6 gre vrf veth
[  862.229458] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  862.230368] Workqueue: netns cleanup_net
[  862.230696] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[ 862.231129] 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 a0 70 cf ad 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 a0 70 cf ad 	mov    $0xffffffffadcf70a0,%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
[  862.232529] RSP: 0018:ffffa46d00063d78 EFLAGS: 00010286
[  862.232957] RAX: 0000000000000000 RBX: ffff8f7a02580000 RCX: 00000000ffffdfff
[  862.233525] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  862.234093] RBP: ffff8f7a025805f8 R08: ffffffffae164508 R09: 00000000ffffdfff
[  862.234624] R10: ffffffffae084520 R11: ffffffffae134520 R12: ffff8f7a02580000
[  862.235191] R13: ffffa46d00063e08 R14: ffff8f7a02580b60 R15: ffff8f7a06028050
[  862.235740] FS:  0000000000000000(0000) GS:ffff8f7a3ed00000(0000) knlGS:0000000000000000
[  862.236383] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  862.236841] CR2: 00000000004e1f88 CR3: 00000000027f8005 CR4: 00000000001706f0
[  862.237409] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  862.237985] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  862.238371] Call Trace:
[  862.238511]  <TASK>
[  862.238638] ? __warn (kernel/panic.c:677) 
[  862.238834] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  862.239100] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  862.239307] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  862.239500] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  862.239709] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  862.239957] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  862.240209] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  862.240461] br_sysfs_delbr (net/bridge/br_sysfs_br.c:1086) bridge
[  862.240761] br_dev_delete (net/bridge/br_if.c:396) bridge
[  862.241127] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  862.241421] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  862.241621] ? process_one_work (kernel/workqueue.c:2606) 
[  862.241858] process_one_work (kernel/workqueue.c:2638) 
[  862.242089] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  862.242296] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  862.242529] kthread (kernel/kthread.c:388) 
[  862.242707] ? __pfx_kthread (kernel/kthread.c:341) 
[  862.242926] ret_from_fork (arch/x86/kernel/process.c:153) 
[  862.243128] ? __pfx_kthread (kernel/kthread.c:341) 
[  862.243335] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  862.245983] ------------[ cut here ]------------
| [  862.246232] sysfs group 'bridge' not found for kobject 'br2'
| [  862.246555] WARNING: CPU: 2 PID: 11 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  862.247005] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel bridge stp llc act_gact cls_flower sch_ingress 8021q ip6_gre ip6_tunnel tunnel6 gre vrf veth
[  862.248233] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  862.248848] Workqueue: netns cleanup_net
[  862.249102] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 862.249367] 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 88 06 cf ad 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 88 06 cf ad 	mov    $0xffffffffadcf0688,%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)
	...
[  862.250356] RSP: 0018:ffffa46d00063d70 EFLAGS: 00010286
[  862.250638] RAX: 0000000000000000 RBX: ffffffffc069bc60 RCX: 00000000ffffdfff
[  862.251033] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  862.251412] RBP: 0000000000000000 R08: ffffffffae164508 R09: 00000000ffffdfff
[  862.251788] R10: ffffffffae084520 R11: ffffffffae134520 R12: ffff8f7a025805f8
[  862.252182] R13: ffffa46d00063e08 R14: ffff8f7a02580b60 R15: ffff8f7a06028050
[  862.252562] FS:  0000000000000000(0000) GS:ffff8f7a3ed00000(0000) knlGS:0000000000000000
[  862.253028] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  862.253339] CR2: 00000000004e1f88 CR3: 00000000027f8005 CR4: 00000000001706f0
[  862.253721] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  862.254113] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  862.254491] Call Trace:
[  862.254629]  <TASK>
[  862.254750] ? __warn (kernel/panic.c:677) 
[  862.254933] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  862.255166] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  862.255373] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  862.255568] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  862.255785] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  862.256025] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  862.256259] br_dev_delete (net/bridge/br_if.c:396) bridge
[  862.256524] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  862.256817] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  862.257022] ? process_one_work (kernel/workqueue.c:2606) 
[  862.257254] process_one_work (kernel/workqueue.c:2638) 
[  862.257476] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  862.257698] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  862.257948] kthread (kernel/kthread.c:388) 
[  862.258125] ? __pfx_kthread (kernel/kthread.c:341) 
[  862.258332] ret_from_fork (arch/x86/kernel/process.c:153) 
[  862.258529] ? __pfx_kthread (kernel/kthread.c:341) 
[  862.258742] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  862.368087] ------------[ cut here ]------------
| [  862.368354] sysfs group 'bridge' not found for kobject 'br2'
| [  862.368680] WARNING: CPU: 2 PID: 11 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  862.369137] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel bridge stp llc act_gact cls_flower sch_ingress 8021q ip6_gre ip6_tunnel tunnel6 gre vrf veth
[  862.370362] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  862.370976] Workqueue: netns cleanup_net
[  862.371194] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 862.371461] 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 88 06 cf ad 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 88 06 cf ad 	mov    $0xffffffffadcf0688,%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)
	...
[  862.372446] RSP: 0018:ffffa46d00063d70 EFLAGS: 00010286
[  862.372729] RAX: 0000000000000000 RBX: ffffffffc069bc60 RCX: 00000000ffffdfff
[  862.373119] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  862.373501] RBP: 0000000000000000 R08: ffffffffae164508 R09: 00000000ffffdfff
[  862.373882] R10: ffffffffae084520 R11: ffffffffae134520 R12: ffff8f7a020985f8
[  862.374270] R13: ffffa46d00063e08 R14: ffff8f7a02098b60 R15: ffffffffaf613dd0
[  862.374651] FS:  0000000000000000(0000) GS:ffff8f7a3ed00000(0000) knlGS:0000000000000000
[  862.375093] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  862.375412] CR2: 00007f66d44011b4 CR3: 000000002644c002 CR4: 00000000001706f0
[  862.375797] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  862.376196] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  862.376574] Call Trace:
[  862.376713]  <TASK>
[  862.376836] ? __warn (kernel/panic.c:677) 
[  862.377027] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  862.377257] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  862.377469] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  862.377672] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  862.377882] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  862.378124] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  862.378354] br_dev_delete (net/bridge/br_if.c:396) bridge
[  862.378616] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  862.378903] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  862.379116] ? process_one_work (kernel/workqueue.c:2606) 
[  862.379344] process_one_work (kernel/workqueue.c:2638) 
[  862.379567] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  862.379774] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  862.380019] kthread (kernel/kthread.c:388) 
[  862.380200] ? __pfx_kthread (kernel/kthread.c:341) 
[  862.380405] ret_from_fork (arch/x86/kernel/process.c:153) 
[  862.380606] ? __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