======================================
| xx__-> [   16.232580][   T12] ==================================================================
| [   16.232912][   T12] BUG: KASAN: slab-use-after-free in kobject_put (lib/kobject.c:733)
| [   16.233296][   T12] Read of size 1 at addr ffff888004b39694 by task kworker/u16:0/12
| [   16.233699][   T12]
[   16.233851][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   16.233856][   T12] Workqueue: netns cleanup_net
[   16.233867][   T12] Call Trace:
[   16.233870][   T12]  <TASK>
[   16.233874][   T12]  dump_stack_lvl (lib/dump_stack.c:123)
[   16.233883][   T12]  print_address_description.constprop.0 (mm/kasan/report.c:379)
[   16.233895][   T12]  ? kobject_put (lib/kobject.c:733)
[   16.233902][   T12]  print_report (mm/kasan/report.c:483)
[   16.233908][   T12]  ? kobject_put (lib/kobject.c:733)
[   16.233913][   T12]  ? kasan_addr_to_slab (./include/linux/mm.h:1245 mm/kasan/../slab.h:191 mm/kasan/common.c:47)
[   16.233919][   T12]  ? kobject_put (lib/kobject.c:733)
[   16.233924][   T12]  kasan_report (mm/kasan/report.c:597)
[   16.233931][   T12]  ? kobject_put (lib/kobject.c:733)
[   16.233941][   T12]  kobject_put (lib/kobject.c:733)
[   16.233946][   T12]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   16.233954][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   16.233959][   T12]  ? generic_xdp_install (net/core/dev.c:11630)
[   16.233970][   T12]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   16.233977][   T12]  ? netns_get (net/core/net_namespace.c:223)
[   16.233981][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   16.233991][   T12]  cleanup_net (net/core/net_namespace.c:698)
[   16.233997][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[   16.234004][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   16.234014][   T12]  process_one_work (kernel/workqueue.c:3268)
[   16.234028][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   16.234038][   T12]  ? assign_work (kernel/workqueue.c:1206)
[   16.234045][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   16.234056][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[   16.234062][   T12]  kthread (kernel/kthread.c:463)
[   16.234068][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   16.234073][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   16.234080][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   16.234088][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   16.234094][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   16.234100][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[   16.234105][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   16.234110][   T12]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   16.264106][   T12] refcount_t: underflow; use-after-free.
| [   16.264342][   T12] WARNING: CPU: 2 PID: 12 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [   16.264710][   T12] Modules linked in: veth
| [   16.265312][   T12] Tainted: [B]=BAD_PAGE
[   16.265483][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   16.265733][   T12] Workqueue: netns cleanup_net
[   16.265937][   T12] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[   16.266205][   T12] Code: 48 92 02 80 fb 01 0f 87 cb 7d d9 fe 83 e3 01 0f 85 51 ff ff ff c6 05 75 48 92 02 01 90 48 c7 c7 a0 8d 85 8d e8 42 93 18 ff 90 <0f> 0b 90 90 e9 33 ff ff ff 48 89 df e8 c0 37 a1 ff e9 ba fe ff ff
All code
========
   0:	48 92                	xchg   %rax,%rdx
   2:	02 80 fb 01 0f 87    	add    -0x78f0fe05(%rax),%al
   8:	cb                   	lret
   9:	7d d9                	jge    0xffffffffffffffe4
   b:	fe 83 e3 01 0f 85    	incb   -0x7af0fe1d(%rbx)
  11:	51                   	push   %rcx
  12:	ff                   	(bad)
  13:	ff                   	(bad)
  14:	ff c6                	inc    %esi
  16:	05 75 48 92 02       	add    $0x2924875,%eax
  1b:	01 90 48 c7 c7 a0    	add    %edx,-0x5f3838b8(%rax)
  21:	8d 85 8d e8 42 93    	lea    -0x6cbd1773(%rbp),%eax
  27:	18 ff                	sbb    %bh,%bh
  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 37 a1 ff       	call   0xffffffffffa137fb
  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 37 a1 ff       	call   0xffffffffffa137d1
  11:	e9 ba fe ff ff       	jmp    0xfffffffffffffed0
[   16.266870][   T12] RSP: 0018:ffffc900000c7a08 EFLAGS: 00010282
[   16.267118][   T12] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[   16.267415][   T12] RDX: 0000000000000002 RSI: 0000000000000004 RDI: 0000000000000001
[   16.267726][   T12] RBP: 0000000000000003 R08: 0000000000000000 R09: fffffbfff1c3e134
[   16.268004][   T12] R10: 0000000000000003 R11: ffffc900000c7580 R12: 0000000000000001
[   16.268300][   T12] R13: dffffc0000000000 R14: dead000000000122 R15: dead000000000100
[   16.268699][   T12] FS:  0000000000000000(0000) GS:ffff8880a6d10000(0000) knlGS:0000000000000000
[   16.269027][   T12] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   16.269414][   T12] CR2: 00007fcd2ae47760 CR3: 00000000098af002 CR4: 0000000000772ef0
[   16.269785][   T12] PKRU: 55555554
[   16.269924][   T12] Call Trace:
[   16.270077][   T12]  <TASK>
[   16.270197][   T12]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   16.270513][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   16.270738][   T12]  ? generic_xdp_install (net/core/dev.c:11630)
[   16.270925][   T12]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   16.271139][   T12]  ? netns_get (net/core/net_namespace.c:223)
[   16.271467][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   16.271679][   T12]  cleanup_net (net/core/net_namespace.c:698)
[   16.271866][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[   16.272066][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   16.272370][   T12]  process_one_work (kernel/workqueue.c:3268)
[   16.272602][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   16.272801][   T12]  ? assign_work (kernel/workqueue.c:1206)
[   16.272986][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   16.273294][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[   16.273498][   T12]  kthread (kernel/kthread.c:463)
[   16.273659][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   16.273849][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   16.274128][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   16.274338][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   16.274547][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   16.274758][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[   16.275040][   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