======================================
| xx__-> [   87.680660][   T70] ==================================================================
| [   87.681120][   T70] BUG: KASAN: slab-use-after-free in kobject_put (lib/kobject.c:733)
| [   87.681530][   T70] Read of size 1 at addr ffff8880077416c4 by task kworker/u16:1/70
| [   87.681922][   T70]
[   87.682075][   T70] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   87.682079][   T70] Workqueue: netns cleanup_net
[   87.682091][   T70] Call Trace:
[   87.682095][   T70]  <TASK>
[   87.682099][   T70]  dump_stack_lvl (lib/dump_stack.c:123)
[   87.682107][   T70]  print_address_description.constprop.0 (mm/kasan/report.c:379)
[   87.682118][   T70]  ? kobject_put (lib/kobject.c:733)
[   87.682125][   T70]  print_report (mm/kasan/report.c:483)
[   87.682130][   T70]  ? kobject_put (lib/kobject.c:733)
[   87.682136][   T70]  ? kasan_addr_to_slab (./include/linux/mm.h:1245 mm/kasan/../slab.h:191 mm/kasan/common.c:47)
[   87.682142][   T70]  ? kobject_put (lib/kobject.c:733)
[   87.682147][   T70]  kasan_report (mm/kasan/report.c:597)
[   87.682154][   T70]  ? kobject_put (lib/kobject.c:733)
[   87.682164][   T70]  kobject_put (lib/kobject.c:733)
[   87.682170][   T70]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   87.682179][   T70]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   87.682185][   T70]  ? generic_xdp_install (net/core/dev.c:11630)
[   87.682190][   T70]  ? net_generic (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:897 ./include/net/netns/generic.h:48)
[   87.682205][   T70]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   87.682215][   T70]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   87.682220][   T70]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   87.682231][   T70]  cleanup_net (net/core/net_namespace.c:698)
[   87.682238][   T70]  ? net_passive_dec (net/core/net_namespace.c:660)
[   87.682246][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   87.682258][   T70]  process_one_work (kernel/workqueue.c:3268)
[   87.682271][   T70]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   87.682282][   T70]  ? assign_work (kernel/workqueue.c:1206)
[   87.682290][   T70]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   87.682301][   T70]  ? rescuer_thread (kernel/workqueue.c:3373)
[   87.682307][   T70]  kthread (kernel/kthread.c:463)
[   87.682313][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   87.682318][   T70]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   87.682324][   T70]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   87.682329][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   87.682335][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   87.682341][   T70]  ret_from_fork (arch/x86/kernel/process.c:164)
[   87.682346][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   87.682351][   T70]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   87.708319][   T70] refcount_t: underflow; use-after-free.
| [   87.708574][   T70] WARNING: CPU: 0 PID: 70 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [   87.709466][   T70] Modules linked in: xt_conntrack nf_conntrack nf_defrag_ipv4 nft_compat nf_tables nf_defrag_ipv6
| [   87.710615][   T70] Tainted: [B]=BAD_PAGE
[   87.710838][   T70] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   87.711161][   T70] Workqueue: netns cleanup_net
[   87.711440][   T70] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[   87.711822][   T70] 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 25 b1 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 25 b1 	mov    $0xffffffffb125ba40,%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
[   87.712728][   T70] RSP: 0018:ffffc900004b7a08 EFLAGS: 00010282
[   87.713081][   T70] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[   87.713474][   T70] RDX: 0000000000000002 RSI: 0000000000000004 RDI: 0000000000000001
[   87.713809][   T70] RBP: 0000000000000003 R08: 0000000000000000 R09: fffffbfff6440934
[   87.714182][   T70] R10: 0000000000000003 R11: ffffc900004b7580 R12: 0000000000000001
[   87.714560][   T70] R13: dffffc0000000000 R14: dead000000000122 R15: dead000000000100
[   87.714928][   T70] FS:  0000000000000000(0000) GS:ffff8880b3508000(0000) knlGS:0000000000000000
[   87.715377][   T70] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   87.715693][   T70] CR2: 00007f769e04d840 CR3: 0000000078d49004 CR4: 0000000000772ef0
[   87.716098][   T70] PKRU: 55555554
[   87.716302][   T70] Call Trace:
[   87.716495][   T70]  <TASK>
[   87.716626][   T70]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   87.716904][   T70]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   87.717178][   T70]  ? generic_xdp_install (net/core/dev.c:11630)
[   87.717603][   T70]  ? net_generic (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:897 ./include/net/netns/generic.h:48)
[   87.717884][   T70]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   87.718341][   T70]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   87.718598][   T70]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   87.718865][   T70]  cleanup_net (net/core/net_namespace.c:698)
[   87.719283][   T70]  ? net_passive_dec (net/core/net_namespace.c:660)
[   87.719878][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   87.720128][   T70]  process_one_work (kernel/workqueue.c:3268)
[   87.720389][   T70]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   87.720649][   T70]  ? assign_work (kernel/workqueue.c:1206)
[   87.720924][   T70]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   87.721190][   T70]  ? rescuer_thread (kernel/workqueue.c:3373)
[   87.721447][   T70]  kthread (kernel/kthread.c:463)
[   87.721643][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   87.722001][   T70]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   87.722271][   T70]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   87.722530][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   87.722797][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   87.723251][   T70]  ret_from_fork (arch/x86/kernel/process.c:164)
[   87.723512][   T70]  ? 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