======================================
| xx__-> [  170.449501][   T12] ==================================================================
| [  170.449816][   T12] BUG: KASAN: slab-use-after-free in kobject_put (lib/kobject.c:733)
| [  170.450094][   T12] Read of size 1 at addr ffff8880096a96ac by task kworker/u16:0/12
| [  170.450347][   T12]
[  170.450449][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  170.450452][   T12] Workqueue: netns cleanup_net
[  170.450458][   T12] Call Trace:
[  170.450460][   T12]  <TASK>
[  170.450463][   T12]  dump_stack_lvl (lib/dump_stack.c:123)
[  170.450469][   T12]  print_address_description.constprop.0 (mm/kasan/report.c:379)
[  170.450476][   T12]  ? kobject_put (lib/kobject.c:733)
[  170.450480][   T12]  print_report (mm/kasan/report.c:483)
[  170.450484][   T12]  ? kobject_put (lib/kobject.c:733)
[  170.450487][   T12]  ? kasan_addr_to_slab (./include/linux/mm.h:1245 mm/kasan/../slab.h:191 mm/kasan/common.c:47)
[  170.450491][   T12]  ? kobject_put (lib/kobject.c:733)
[  170.450494][   T12]  kasan_report (mm/kasan/report.c:597)
[  170.450499][   T12]  ? kobject_put (lib/kobject.c:733)
[  170.450504][   T12]  kobject_put (lib/kobject.c:733)
[  170.450508][   T12]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[  170.450513][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[  170.450517][   T12]  ? generic_xdp_install (net/core/dev.c:11630)
[  170.450524][   T12]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[  170.450531][   T12]  ? netns_get (net/core/net_namespace.c:223)
[  170.450534][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  170.450540][   T12]  cleanup_net (net/core/net_namespace.c:698)
[  170.450543][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[  170.450547][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  170.450553][   T12]  process_one_work (kernel/workqueue.c:3268)
[  170.450560][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  170.450566][   T12]  ? assign_work (kernel/workqueue.c:1206)
[  170.450570][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  170.450576][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[  170.450579][   T12]  kthread (kernel/kthread.c:463)
[  170.450583][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  170.450586][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  170.450592][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  170.450597][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  170.450600][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  170.450603][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[  170.450607][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  170.450609][   T12]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [  170.472536][   T12] refcount_t: underflow; use-after-free.
| [  170.472761][   T12] WARNING: CPU: 2 PID: 12 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [  170.473851][   T12] Modules linked in: dummy veth nf_log_syslog nft_log nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nf_tables
| [  170.474890][   T12] Tainted: [B]=BAD_PAGE
[  170.475087][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  170.475391][   T12] Workqueue: netns cleanup_net
[  170.475634][   T12] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[  170.475914][   T12] Code: 83 90 02 80 fb 01 0f 87 95 6b d6 fe 83 e3 01 0f 85 51 ff ff ff c6 05 b1 83 90 02 01 90 48 c7 c7 a0 de 65 aa e8 c2 8b 15 ff 90 <0f> 0b 90 90 e9 33 ff ff ff 48 89 df e8 f0 34 a1 ff e9 ba fe ff ff
All code
========
   0:	83 90 02 80 fb 01 0f 	adcl   $0xf,0x1fb8002(%rax)
   7:	87 95 6b d6 fe 83    	xchg   %edx,-0x7c012995(%rbp)
   d:	e3 01                	jrcxz  0x10
   f:	0f 85 51 ff ff ff    	jne    0xffffffffffffff66
  15:	c6 05 b1 83 90 02 01 	movb   $0x1,0x29083b1(%rip)        # 0x29083cd
  1c:	90                   	nop
  1d:	48 c7 c7 a0 de 65 aa 	mov    $0xffffffffaa65dea0,%rdi
  24:	e8 c2 8b 15 ff       	call   0xffffffffff158beb
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	e9 33 ff ff ff       	jmp    0xffffffffffffff66
  33:	48 89 df             	mov    %rbx,%rdi
  36:	e8 f0 34 a1 ff       	call   0xffffffffffa1352b
  3b:	e9 ba fe ff ff       	jmp    0xfffffffffffffefa

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	e9 33 ff ff ff       	jmp    0xffffffffffffff3c
   9:	48 89 df             	mov    %rbx,%rdi
   c:	e8 f0 34 a1 ff       	call   0xffffffffffa13501
  11:	e9 ba fe ff ff       	jmp    0xfffffffffffffed0
[  170.476632][   T12] RSP: 0000:ffffc900000c7a08 EFLAGS: 00010282
[  170.476908][   T12] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[  170.477236][   T12] RDX: 0000000000000002 RSI: 0000000000000004 RDI: 0000000000000001
[  170.477578][   T12] RBP: 0000000000000003 R08: 0000000000000000 R09: fffffbfff55fe220
[  170.477983][   T12] R10: 0000000000000003 R11: ffffc900000c7580 R12: 0000000000000001
[  170.478457][   T12] R13: dffffc0000000000 R14: dead000000000122 R15: dead000000000100
[  170.478889][   T12] FS:  0000000000000000(0000) GS:ffff888089eec000(0000) knlGS:0000000000000000
[  170.479402][   T12] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  170.479787][   T12] CR2: 00007fb784577fe0 CR3: 0000000016335001 CR4: 0000000000772ef0
[  170.480157][   T12] PKRU: 55555554
[  170.480315][   T12] Call Trace:
[  170.480471][   T12]  <TASK>
[  170.480586][   T12]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[  170.480786][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[  170.480995][   T12]  ? generic_xdp_install (net/core/dev.c:11630)
[  170.481283][   T12]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[  170.481496][   T12]  ? netns_get (net/core/net_namespace.c:223)
[  170.481690][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  170.481889][   T12]  cleanup_net (net/core/net_namespace.c:698)
[  170.482097][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[  170.482289][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  170.482490][   T12]  process_one_work (kernel/workqueue.c:3268)
[  170.482692][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  170.482884][   T12]  ? assign_work (kernel/workqueue.c:1206)
[  170.483179][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  170.483376][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[  170.483575][   T12]  kthread (kernel/kthread.c:463)
[  170.483728][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  170.483918][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  170.484122][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  170.484323][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  170.484529][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  170.484720][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[  170.485007][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)


Finger prints:
print_report:kasan_report:kobject_put:netdev_run_todo:ops_undo_list
refcount_warn_saturate:netdev_run_todo:ops_undo_list:cleanup_net:process_one_work