======================================
| xx__-> [   21.113350][   T68] ==================================================================
| [   21.113678][   T68] BUG: KASAN: slab-use-after-free in kobject_put (lib/kobject.c:733)
| [   21.113985][   T68] Read of size 1 at addr ffff8880072946c4 by task kworker/u16:1/68
| [   21.114283][   T68]
[   21.114392][   T68] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   21.114395][   T68] Workqueue: netns cleanup_net
[   21.114403][   T68] Call Trace:
[   21.114405][   T68]  <TASK>
[   21.114409][   T68]  dump_stack_lvl (lib/dump_stack.c:123)
[   21.114414][   T68]  print_address_description.constprop.0 (mm/kasan/report.c:379)
[   21.114421][   T68]  ? kobject_put (lib/kobject.c:733)
[   21.114425][   T68]  print_report (mm/kasan/report.c:483)
[   21.114428][   T68]  ? kobject_put (lib/kobject.c:733)
[   21.114431][   T68]  ? kasan_addr_to_slab (./include/linux/mm.h:1245 mm/kasan/../slab.h:191 mm/kasan/common.c:47)
[   21.114435][   T68]  ? kobject_put (lib/kobject.c:733)
[   21.114438][   T68]  kasan_report (mm/kasan/report.c:597)
[   21.114442][   T68]  ? kobject_put (lib/kobject.c:733)
[   21.114447][   T68]  kobject_put (lib/kobject.c:733)
[   21.114451][   T68]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   21.114457][   T68]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   21.114460][   T68]  ? generic_xdp_install (net/core/dev.c:11630)
[   21.114463][   T68]  ? net_generic (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:897 ./include/net/netns/generic.h:48)
[   21.114471][   T68]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   21.114477][   T68]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   21.114480][   T68]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   21.114486][   T68]  cleanup_net (net/core/net_namespace.c:698)
[   21.114490][   T68]  ? net_passive_dec (net/core/net_namespace.c:660)
[   21.114495][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   21.114502][   T68]  process_one_work (kernel/workqueue.c:3268)
[   21.114511][   T68]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   21.114516][   T68]  ? assign_work (kernel/workqueue.c:1206)
[   21.114521][   T68]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   21.114526][   T68]  ? rescuer_thread (kernel/workqueue.c:3373)
[   21.114530][   T68]  kthread (kernel/kthread.c:463)
[   21.114535][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   21.114537][   T68]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   21.114542][   T68]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   21.114546][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   21.114549][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   21.114553][   T68]  ret_from_fork (arch/x86/kernel/process.c:164)
[   21.114555][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   21.114558][   T68]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   21.136378][   T68] refcount_t: underflow; use-after-free.
| [   21.136563][   T68] WARNING: CPU: 3 PID: 68 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [   21.137061][   T68] Modules linked in: nft_compat nf_tables
| [   21.137655][   T68] Tainted: [B]=BAD_PAGE
[   21.137815][   T68] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   21.138029][   T68] Workqueue: netns cleanup_net
[   21.138224][   T68] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[   21.138452][   T68] Code: cc 38 03 80 fb 01 0f 87 29 33 d7 fe 83 e3 01 0f 85 51 ff ff ff c6 05 17 cc 38 03 01 90 48 c7 c7 40 ba 85 85 e8 62 d6 16 ff 90 <0f> 0b 90 90 e9 33 ff ff ff 48 89 df e8 c0 9d a0 ff e9 ba fe ff ff
All code
========
   0:	cc                   	int3
   1:	38 03                	cmp    %al,(%rbx)
   3:	80 fb 01             	cmp    $0x1,%bl
   6:	0f 87 29 33 d7 fe    	ja     0xfffffffffed73335
   c:	83 e3 01             	and    $0x1,%ebx
   f:	0f 85 51 ff ff ff    	jne    0xffffffffffffff66
  15:	c6 05 17 cc 38 03 01 	movb   $0x1,0x338cc17(%rip)        # 0x338cc33
  1c:	90                   	nop
  1d:	48 c7 c7 40 ba 85 85 	mov    $0xffffffff8585ba40,%rdi
  24:	e8 62 d6 16 ff       	call   0xffffffffff16d68b
  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 c0 9d a0 ff       	call   0xffffffffffa09dfb
  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 c0 9d a0 ff       	call   0xffffffffffa09dd1
  11:	e9 ba fe ff ff       	jmp    0xfffffffffffffed0
[   21.139053][   T68] RSP: 0018:ffffc90000497a08 EFLAGS: 00010282
[   21.139272][   T68] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[   21.139537][   T68] RDX: 0000000000000002 RSI: 0000000000000004 RDI: 0000000000000001
[   21.139797][   T68] RBP: 0000000000000003 R08: 0000000000000000 R09: fffffbfff0d00934
[   21.140043][   T68] R10: 0000000000000003 R11: ffffc90000497580 R12: 0000000000000001
[   21.140302][   T68] R13: dffffc0000000000 R14: dead000000000122 R15: dead000000000100
[   21.140562][   T68] FS:  0000000000000000(0000) GS:ffff8880e5488000(0000) knlGS:0000000000000000
[   21.140856][   T68] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   21.141128][   T68] CR2: 00000000004061e9 CR3: 000000000f7d9004 CR4: 0000000000772ef0
[   21.141398][   T68] PKRU: 55555554
[   21.141530][   T68] Call Trace:
[   21.141654][   T68]  <TASK>
[   21.141740][   T68]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   21.141926][   T68]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   21.142100][   T68]  ? generic_xdp_install (net/core/dev.c:11630)
[   21.142269][   T68]  ? net_generic (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:897 ./include/net/netns/generic.h:48)
[   21.142445][   T68]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   21.142610][   T68]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   21.142777][   T68]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   21.142938][   T68]  cleanup_net (net/core/net_namespace.c:698)
[   21.143097][   T68]  ? net_passive_dec (net/core/net_namespace.c:660)
[   21.143267][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   21.143449][   T68]  process_one_work (kernel/workqueue.c:3268)
[   21.143672][   T68]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   21.143868][   T68]  ? assign_work (kernel/workqueue.c:1206)
[   21.144037][   T68]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   21.144209][   T68]  ? rescuer_thread (kernel/workqueue.c:3373)
[   21.144430][   T68]  kthread (kernel/kthread.c:463)
[   21.144555][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   21.144727][   T68]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   21.144902][   T68]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   21.145066][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   21.145301][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   21.145489][   T68]  ret_from_fork (arch/x86/kernel/process.c:164)
[   21.145651][   T68]  ? 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