======================================
| [  124.715479] ------------[ cut here ]------------
| [  124.715739] refcount_t: underflow; use-after-free.
| [  124.716034] WARNING: CPU: 2 PID: 67 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
| [  124.716470] Modules linked in: act_tunnel_key cls_flower bareudp mpls_iptunnel mpls_router act_mirred cls_matchall ip6_gre gre nft_chain_nat xt_nat nf_nat vxlan cls_bpf sch_ingress xt_conntrack nf_conntrack nf_defrag_ipv4 nft_compat nf_tables nf_defrag_ipv6 sctp_diag sctp ip6_udp_tunnel udp_tunnel libcrc32c
[  124.718508] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  124.719559] Workqueue: netns cleanup_net
[  124.719960] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[ 124.720395] Code: 0b 90 90 c3 cc cc cc cc 80 3d 69 d4 67 01 00 0f 85 75 ff ff ff c6 05 5c d4 67 01 01 90 48 c7 c7 b8 37 f3 89 e8 a1 26 b4 ff 90 <0f> 0b 90 90 c3 cc cc cc cc 80 3d 3c d4 67 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 69 d4 67 01 00 	cmpb   $0x0,0x167d469(%rip)        # 0x167d478
   f:	0f 85 75 ff ff ff    	jne    0xffffffffffffff8a
  15:	c6 05 5c d4 67 01 01 	movb   $0x1,0x167d45c(%rip)        # 0x167d478
  1c:	90                   	nop
  1d:	48 c7 c7 b8 37 f3 89 	mov    $0xffffffff89f337b8,%rdi
  24:	e8 a1 26 b4 ff       	call   0xffffffffffb426ca
  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 3c d4 67 01 00 	cmpb   $0x0,0x167d43c(%rip)        # 0x167d476
  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 3c d4 67 01 00 	cmpb   $0x0,0x167d43c(%rip)        # 0x167d44c
  10:	0f 85 4a ff ff ff    	jne    0xffffffffffffff60
[  124.721782] RSP: 0018:ffffb0e90025bd78 EFLAGS: 00010286
[  124.722098] RAX: 0000000000000000 RBX: ffff8f0a02a14000 RCX: 00000000ffffdfff
[  124.722515] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  124.722897] RBP: ffff8f0a02a14610 R08: ffffffff8a378508 R09: 00000000ffffdfff
[  124.723275] R10: ffffffff8a298520 R11: ffffffff8a348520 R12: ffff8f0a02a14000
[  124.723653] R13: ffffb0e90025be08 R14: ffff8f0a02a14b80 R15: ffff8f0a05704550
[  124.724038] FS:  0000000000000000(0000) GS:ffff8f0a3ed00000(0000) knlGS:0000000000000000
[  124.724462] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  124.724772] CR2: 00007f29f2d01000 CR3: 000000001e860004 CR4: 0000000000770ef0
[  124.725148] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  124.725522] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  124.725910] PKRU: 55555554
[  124.726056] Call Trace:
[  124.726199]  <TASK>
[  124.726323] ? __warn (kernel/panic.c:677) 
[  124.726501] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  124.726752] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  124.726957] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  124.727146] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  124.727348] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  124.727574] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  124.727813] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  124.728064] br_sysfs_delbr (net/bridge/br_sysfs_br.c:1086) 
[  124.728269] br_dev_delete (net/bridge/br_if.c:396) 
[  124.728463] br_net_exit_batch_rtnl (net/bridge/br.c:369) 
[  124.728695] cleanup_net (net/core/net_namespace.c:630) 
[  124.728981] ? process_one_work (kernel/workqueue.c:2606) 
[  124.729316] process_one_work (kernel/workqueue.c:2633) 
[  124.729640] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  124.729961] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  124.730302] kthread (kernel/kthread.c:388) 
[  124.730528] ? __pfx_kthread (kernel/kthread.c:341) 
[  124.730730] ret_from_fork (arch/x86/kernel/process.c:147) 
[  124.730937] ? __pfx_kthread (kernel/kthread.c:341) 
[  124.731137] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  124.733756] ------------[ cut here ]------------
| [  124.734067] sysfs group 'bridge' not found for kobject 'br0'
| [  124.734579] WARNING: CPU: 1 PID: 67 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  124.735020] Modules linked in: act_tunnel_key cls_flower bareudp mpls_iptunnel mpls_router act_mirred cls_matchall ip6_gre gre nft_chain_nat xt_nat nf_nat vxlan cls_bpf sch_ingress xt_conntrack nf_conntrack nf_defrag_ipv4 nft_compat nf_tables nf_defrag_ipv6 sctp_diag sctp ip6_udp_tunnel udp_tunnel libcrc32c
[  124.736920] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  124.737891] Workqueue: netns cleanup_net
[  124.738285] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 124.738550] Code: 48 89 ef 5d 41 5c e9 7a ad ff ff 48 89 ef e8 12 9b ff ff eb d1 90 49 8b 14 24 48 8b 33 48 c7 c7 a0 cd f2 89 e8 ac 67 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 7a ad ff ff       	jmp    0xffffffffffffad85
   b:	48 89 ef             	mov    %rbp,%rdi
   e:	e8 12 9b ff ff       	call   0xffffffffffff9b25
  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 a0 cd f2 89 	mov    $0xffffffff89f2cda0,%rdi
  24:	e8 ac 67 c5 ff       	call   0xffffffffffc567d5
  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)
	...
[  124.739925] RSP: 0018:ffffb0e90025bd70 EFLAGS: 00010286
[  124.740296] RAX: 0000000000000000 RBX: ffffffff89b472c0 RCX: 00000000ffffdfff
[  124.740913] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  124.741544] RBP: 0000000000000000 R08: ffffffff8a378508 R09: 00000000ffffdfff
[  124.742235] R10: ffffffff8a298520 R11: ffffffff8a348520 R12: ffff8f0a02a14610
[  124.742925] R13: ffffb0e90025be08 R14: ffff8f0a02a14b80 R15: ffff8f0a05704550
[  124.743600] FS:  0000000000000000(0000) GS:ffff8f0a3ec80000(0000) knlGS:0000000000000000
[  124.744337] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  124.744865] CR2: 0000561bafc81dec CR3: 000000001e860002 CR4: 0000000000770ef0
[  124.745512] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  124.746181] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  124.746808] PKRU: 55555554
[  124.747090] Call Trace:
[  124.747341]  <TASK>
[  124.747536] ? __warn (kernel/panic.c:677) 
[  124.747791] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  124.748022] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  124.748220] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  124.748484] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  124.748700] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  124.748937] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  124.749171] br_dev_delete (net/bridge/br_if.c:396) 
[  124.749376] br_net_exit_batch_rtnl (net/bridge/br.c:369) 
[  124.749616] cleanup_net (net/core/net_namespace.c:630) 
[  124.749846] ? process_one_work (kernel/workqueue.c:2606) 
[  124.750202] process_one_work (kernel/workqueue.c:2633) 
[  124.750541] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  124.750789] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  124.751064] kthread (kernel/kthread.c:388) 
[  124.751337] ? __pfx_kthread (kernel/kthread.c:341) 
[  124.751632] ret_from_fork (arch/x86/kernel/process.c:147) 
[  124.752002] ? __pfx_kthread (kernel/kthread.c:341) 
[  124.752335] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  124.876098] ------------[ cut here ]------------
| [  124.876359] sysfs group 'bridge' not found for kobject 'br0'
| [  124.876674] WARNING: CPU: 1 PID: 67 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  124.877114] Modules linked in: act_tunnel_key cls_flower bareudp mpls_iptunnel mpls_router act_mirred cls_matchall ip6_gre gre nft_chain_nat xt_nat nf_nat vxlan cls_bpf sch_ingress xt_conntrack nf_conntrack nf_defrag_ipv4 nft_compat nf_tables nf_defrag_ipv6 sctp_diag sctp ip6_udp_tunnel udp_tunnel libcrc32c
[  124.878981] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  124.879561] Workqueue: netns cleanup_net
[  124.879785] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 124.880058] Code: 48 89 ef 5d 41 5c e9 7a ad ff ff 48 89 ef e8 12 9b ff ff eb d1 90 49 8b 14 24 48 8b 33 48 c7 c7 a0 cd f2 89 e8 ac 67 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 7a ad ff ff       	jmp    0xffffffffffffad85
   b:	48 89 ef             	mov    %rbp,%rdi
   e:	e8 12 9b ff ff       	call   0xffffffffffff9b25
  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 a0 cd f2 89 	mov    $0xffffffff89f2cda0,%rdi
  24:	e8 ac 67 c5 ff       	call   0xffffffffffc567d5
  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)
	...
[  124.881017] RSP: 0018:ffffb0e90025bd70 EFLAGS: 00010286
[  124.881294] RAX: 0000000000000000 RBX: ffffffff89b472c0 RCX: 00000000ffffdfff
[  124.881665] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  124.882044] RBP: 0000000000000000 R08: ffffffff8a378508 R09: 00000000ffffdfff
[  124.882417] R10: ffffffff8a298520 R11: ffffffff8a348520 R12: ffff8f0a0237c610
[  124.882824] R13: ffffb0e90025be08 R14: ffff8f0a0237cb80 R15: ffffffff8b878f90
[  124.883218] FS:  0000000000000000(0000) GS:ffff8f0a3ec80000(0000) knlGS:0000000000000000
[  124.883673] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  124.883997] CR2: 00007f6e6c57d0e0 CR3: 000000001e860003 CR4: 0000000000770ef0
[  124.884363] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  124.884736] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  124.885109] PKRU: 55555554
[  124.885257] Call Trace:
[  124.885403]  <TASK>
[  124.885537] ? __warn (kernel/panic.c:677) 
[  124.885730] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  124.885984] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  124.886194] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  124.886417] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  124.886639] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  124.886884] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  124.887114] br_dev_delete (net/bridge/br_if.c:396) 
[  124.887314] br_net_exit_batch_rtnl (net/bridge/br.c:369) 
[  124.887550] cleanup_net (net/core/net_namespace.c:630) 
[  124.887748] ? process_one_work (kernel/workqueue.c:2606) 
[  124.887977] process_one_work (kernel/workqueue.c:2633) 
[  124.888195] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  124.888405] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  124.888629] kthread (kernel/kthread.c:388) 
[  124.888802] ? __pfx_kthread (kernel/kthread.c:341) 
[  124.889008] ret_from_fork (arch/x86/kernel/process.c:147) 
[  124.889202] ? __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