======================================
| [   97.527295][   T69] ==================================================================
| [   97.527777][   T69] BUG: KASAN: null-ptr-deref in try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
| [   97.528228][   T69] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/69
| [   97.528656][   T69]
[   97.528828][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   97.528833][   T69] Workqueue: netns cleanup_net
[   97.528847][   T69] Call Trace:
[   97.528854][   T69]  <TASK>
[   97.528857][   T69]  dump_stack_lvl (lib/dump_stack.c:123)
[   97.528872][   T69]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   97.528880][   T69]  kasan_report (mm/kasan/report.c:597)
[   97.528890][   T69]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   97.528900][   T69]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   97.528906][   T69]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   97.528915][   T69]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   97.528921][   T69]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   97.528930][   T69]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   97.528939][   T69]  __cancel_work_sync (kernel/workqueue.c:4383)
[   97.528945][   T69]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   97.528955][   T69]  ? netdev_notify_peers (net/core/dev.c:1891)
[   97.528962][   T69]  ? netif_close_many (net/core/dev.c:1959)
[   97.528970][   T69]  netif_close_many (net/core/dev.c:1959)
[   97.528977][   T69]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   97.528986][   T69]  ? __dev_close_many (net/core/dev.c:1949)
[   97.528992][   T69]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   97.529005][   T69]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   97.529015][   T69]  ? mutex_is_locked (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-long.h:38 ./include/linux/atomic/atomic-instrumented.h:3189 kernel/locking/mutex.h:47 kernel/locking/mutex.c:67)
[   97.529021][   T69]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   97.529026][   T69]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   97.529031][   T69]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   97.529036][   T69]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   97.529041][   T69]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   97.529052][   T69]  default_device_exit_batch (net/core/dev.c:13229)
[   97.529058][   T69]  ? unregister_netdev (net/core/dev.c:13204)
[   97.529068][   T69]  ops_undo_list (net/core/net_namespace.c:251)
[   97.529077][   T69]  ? netns_get (net/core/net_namespace.c:223)
[   97.529082][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   97.529092][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   97.529099][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   97.529106][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   97.529118][   T69]  process_one_work (kernel/workqueue.c:3268)
[   97.529130][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   97.529140][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   97.529148][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   97.529162][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   97.529169][   T69]  kthread (kernel/kthread.c:463)
[   97.529178][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   97.529182][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   97.529190][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   97.529198][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   97.529204][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   97.529211][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   97.529215][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   97.529221][   T69]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   97.545710][   T69] #PF: error_code(0x0002) - not-present page
| [   97.546216][   T69] PGD 0 P4D 0
| [   97.546430][   T69] Oops: Oops: 0002 [#1] SMP KASAN
| [   97.547516][   T69] Tainted: [B]=BAD_PAGE
[   97.547733][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   97.548081][   T69] Workqueue: netns cleanup_net
[   97.548377][   T69] RIP: 0010:try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   97.548939][   T69] Code: 00 41 89 c0 b8 01 00 00 00 45 85 c0 74 0f 48 83 c4 10 5b 5d 41 5c 41 5d 41 5e 41 5f c3 be 08 00 00 00 48 89 df e8 6f 7d 81 00 <f0> 48 0f ba 2b 00 72 11 48 83 c4 10 31 c0 5b 5d 41 5c 41 5d 41 5e
All code
========
   0:	00 41 89             	add    %al,-0x77(%rcx)
   3:	c0 b8 01 00 00 00 45 	sarb   $0x45,0x1(%rax)
   a:	85 c0                	test   %eax,%eax
   c:	74 0f                	je     0x1d
   e:	48 83 c4 10          	add    $0x10,%rsp
  12:	5b                   	pop    %rbx
  13:	5d                   	pop    %rbp
  14:	41 5c                	pop    %r12
  16:	41 5d                	pop    %r13
  18:	41 5e                	pop    %r14
  1a:	41 5f                	pop    %r15
  1c:	c3                   	ret
  1d:	be 08 00 00 00       	mov    $0x8,%esi
  22:	48 89 df             	mov    %rbx,%rdi
  25:	e8 6f 7d 81 00       	call   0x817d99
  2a:*	f0 48 0f ba 2b 00    	lock btsq $0x0,(%rbx)		<-- trapping instruction
  30:	72 11                	jb     0x43
  32:	48 83 c4 10          	add    $0x10,%rsp
  36:	31 c0                	xor    %eax,%eax
  38:	5b                   	pop    %rbx
  39:	5d                   	pop    %rbp
  3a:	41 5c                	pop    %r12
  3c:	41 5d                	pop    %r13
  3e:	41 5e                	pop    %r14

Code starting with the faulting instruction
===========================================
   0:	f0 48 0f ba 2b 00    	lock btsq $0x0,(%rbx)
   6:	72 11                	jb     0x19
   8:	48 83 c4 10          	add    $0x10,%rsp
   c:	31 c0                	xor    %eax,%eax
   e:	5b                   	pop    %rbx
   f:	5d                   	pop    %rbp
  10:	41 5c                	pop    %r12
  12:	41 5d                	pop    %r13
  14:	41 5e                	pop    %r14
[   97.549943][   T69] RSP: 0018:ffffc900004a7690 EFLAGS: 00010046
[   97.550478][   T69] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff9b24190a
[   97.550882][   T69] RDX: fffffbfff3edcecd RSI: 0000000000000008 RDI: ffffffff9f6e7660
[   97.551458][   T69] RBP: ffffc900004a76f8 R08: 0000000000000001 R09: fffffbfff3edcecc
[   97.551857][   T69] R10: ffffffff9f6e7667 R11: ffffc900004a7180 R12: 0000000000000000
[   97.552248][   T69] R13: 0000000000000286 R14: ffff888004f8c000 R15: dffffc0000000000
[   97.552832][   T69] FS:  0000000000000000(0000) GS:ffff888090e04000(0000) knlGS:0000000000000000
[   97.553323][   T69] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   97.553682][   T69] CR2: 0000000000000000 CR3: 0000000035159001 CR4: 0000000000772ef0
[   97.554288][   T69] PKRU: 55555554
[   97.554504][   T69] Call Trace:
[   97.554718][   T69]  <TASK>
[   97.554868][   T69]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   97.555343][   T69]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   97.555638][   T69]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   97.555919][   T69]  __cancel_work_sync (kernel/workqueue.c:4383)
[   97.556193][   T69]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   97.556651][   T69]  ? netdev_notify_peers (net/core/dev.c:1891)
[   97.556920][   T69]  ? netif_close_many (net/core/dev.c:1959)
[   97.557201][   T69]  netif_close_many (net/core/dev.c:1959)
[   97.557446][   T69]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   97.557880][   T69]  ? __dev_close_many (net/core/dev.c:1949)
[   97.558164][   T69]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   97.558512][   T69]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   97.558853][   T69]  ? mutex_is_locked (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-long.h:38 ./include/linux/atomic/atomic-instrumented.h:3189 kernel/locking/mutex.h:47 kernel/locking/mutex.c:67)
[   97.559310][   T69]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   97.559587][   T69]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   97.559864][   T69]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   97.560207][   T69]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   97.560670][   T69]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   97.560953][   T69]  default_device_exit_batch (net/core/dev.c:13229)
[   97.561226][   T69]  ? unregister_netdev (net/core/dev.c:13204)
[   97.561506][   T69]  ops_undo_list (net/core/net_namespace.c:251)
[   97.561965][   T69]  ? netns_get (net/core/net_namespace.c:223)
[   97.562233][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   97.562516][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   97.562796][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   97.563070][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   97.563349][   T69]  process_one_work (kernel/workqueue.c:3268)
[   97.563632][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   97.563917][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   97.564373][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   97.564656][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   97.564935][   T69]  kthread (kernel/kthread.c:463)
[   97.565156][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   97.565618][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   97.565896][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   97.566177][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   97.566457][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   97.566914][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   97.567193][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)


Finger prints:
try_to_grab_pending:__cancel_work:__cancel_work_sync:__dev_close_many:netif_close_many
kasan_report:kasan_check_range:try_to_grab_pending:__cancel_work:__cancel_work_sync