======================================
| [  160.276365] ------------[ cut here ]------------
| [  160.276637] refcount_t: underflow; use-after-free.
| [  160.276916] WARNING: CPU: 0 PID: 69 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
| [  160.277377] Modules linked in: act_gact cls_flower vxlan ip6_udp_tunnel udp_tunnel bridge stp llc sch_ingress vrf veth
[  160.278360] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  160.278969] Workqueue: netns cleanup_net
[  160.279193] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[ 160.279482] 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 8f 84 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 8f 84 	mov    $0xffffffff848f70a0,%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
[  160.280465] RSP: 0018:ffffaa020026bd78 EFLAGS: 00010286
[  160.280752] RAX: 0000000000000000 RBX: ffff98c6c2362000 RCX: 00000000ffffdfff
[  160.281144] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  160.281545] RBP: ffff98c6c23625f8 R08: ffffffff84d64508 R09: 00000000ffffdfff
[  160.281992] R10: ffffffff84c84520 R11: ffffffff84d34520 R12: ffff98c6c2362000
[  160.282554] R13: ffffaa020026be08 R14: ffff98c6c2362b60 R15: ffff98c6c6240050
[  160.283079] FS:  0000000000000000(0000) GS:ffff98c6fec00000(0000) knlGS:0000000000000000
[  160.283715] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  160.284175] CR2: 00007f24f8e9d0c8 CR3: 0000000001d02002 CR4: 00000000001706f0
[  160.284725] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  160.285284] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  160.285831] Call Trace:
[  160.286033]  <TASK>
[  160.286222] ? __warn (kernel/panic.c:677) 
[  160.286492] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  160.286869] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  160.287178] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  160.287458] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  160.287761] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  160.288115] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  160.288482] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  160.288850] br_sysfs_delbr (net/bridge/br_sysfs_br.c:1086) bridge
[  160.289293] br_dev_delete (net/bridge/br_if.c:396) bridge
[  160.289665] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  160.290112] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  160.290418] ? process_one_work (kernel/workqueue.c:2606) 
[  160.290738] process_one_work (kernel/workqueue.c:2638) 
[  160.291058] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  160.291370] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  160.291672] kthread (kernel/kthread.c:388) 
[  160.291918] ? __pfx_kthread (kernel/kthread.c:341) 
[  160.292206] ret_from_fork (arch/x86/kernel/process.c:153) 
[  160.292477] ? __pfx_kthread (kernel/kthread.c:341) 
[  160.292778] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  160.296560] ------------[ cut here ]------------
| [  160.296916] sysfs group 'bridge' not found for kobject 'br2'
| [  160.297391] WARNING: CPU: 0 PID: 69 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  160.298015] Modules linked in: act_gact cls_flower vxlan ip6_udp_tunnel udp_tunnel bridge stp llc sch_ingress vrf veth
[  160.299534] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  160.300426] Workqueue: netns cleanup_net
[  160.300740] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 160.301138] 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 8f 84 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 8f 84 	mov    $0xffffffff848f0688,%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)
	...
[  160.302575] RSP: 0018:ffffaa020026bd70 EFLAGS: 00010286
[  160.302855] RAX: 0000000000000000 RBX: ffffffffc0316c60 RCX: 00000000ffffdfff
[  160.303241] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  160.303626] RBP: 0000000000000000 R08: ffffffff84d64508 R09: 00000000ffffdfff
[  160.304001] R10: ffffffff84c84520 R11: ffffffff84d34520 R12: ffff98c6c23625f8
[  160.304386] R13: ffffaa020026be08 R14: ffff98c6c2362b60 R15: ffff98c6c6240050
[  160.304767] FS:  0000000000000000(0000) GS:ffff98c6fec00000(0000) knlGS:0000000000000000
[  160.305207] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  160.305544] CR2: 00007f24f8e9d0c8 CR3: 0000000001d02002 CR4: 00000000001706f0
[  160.305948] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  160.306331] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  160.306714] Call Trace:
[  160.306852]  <TASK>
[  160.306972] ? __warn (kernel/panic.c:677) 
[  160.307162] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  160.307390] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  160.307606] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  160.307803] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  160.308015] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  160.308256] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  160.308494] br_dev_delete (net/bridge/br_if.c:396) bridge
[  160.308762] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  160.309055] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  160.309264] ? process_one_work (kernel/workqueue.c:2606) 
[  160.309499] process_one_work (kernel/workqueue.c:2638) 
[  160.309720] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  160.309928] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  160.310166] kthread (kernel/kthread.c:388) 
[  160.310342] ? __pfx_kthread (kernel/kthread.c:341) 
[  160.310572] ret_from_fork (arch/x86/kernel/process.c:153) 
[  160.310769] ? __pfx_kthread (kernel/kthread.c:341) 
[  160.310973] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  160.429294] ------------[ cut here ]------------
| [  160.429570] sysfs group 'bridge' not found for kobject 'br2'
| [  160.429901] WARNING: CPU: 0 PID: 69 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  160.430356] Modules linked in: act_gact cls_flower vxlan ip6_udp_tunnel udp_tunnel bridge stp llc sch_ingress vrf veth
[  160.431406] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  160.432013] Workqueue: netns cleanup_net
[  160.432240] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 160.432521] 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 8f 84 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 8f 84 	mov    $0xffffffff848f0688,%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)
	...
[  160.433505] RSP: 0018:ffffaa020026bd70 EFLAGS: 00010286
[  160.433791] RAX: 0000000000000000 RBX: ffffffffc0316c60 RCX: 00000000ffffdfff
[  160.434177] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  160.434563] RBP: 0000000000000000 R08: ffffffff84d64508 R09: 00000000ffffdfff
[  160.434941] R10: ffffffff84c84520 R11: ffffffff84d34520 R12: ffff98c6c1cc45f8
[  160.435330] R13: ffffaa020026be08 R14: ffff98c6c1cc4b60 R15: ffffffff86213dd0
[  160.435740] FS:  0000000000000000(0000) GS:ffff98c6fec00000(0000) knlGS:0000000000000000
[  160.436176] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  160.436489] CR2: 000055e08894e618 CR3: 0000000001d02002 CR4: 00000000001706f0
[  160.436866] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  160.437253] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  160.437643] Call Trace:
[  160.437784]  <TASK>
[  160.437909] ? __warn (kernel/panic.c:677) 
[  160.438090] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  160.438329] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  160.438564] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  160.438801] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  160.439074] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  160.439422] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  160.439754] br_dev_delete (net/bridge/br_if.c:396) bridge
[  160.440146] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  160.440570] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  160.440871] ? process_one_work (kernel/workqueue.c:2606) 
[  160.441213] process_one_work (kernel/workqueue.c:2638) 
[  160.441529] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  160.441825] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  160.442175] kthread (kernel/kthread.c:388) 
[  160.442434] ? __pfx_kthread (kernel/kthread.c:341) 
[  160.442734] ret_from_fork (arch/x86/kernel/process.c:153) 
[  160.443021] ? __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