======================================
| [   78.528895][   T69] ==================================================================
| [   78.529265][   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)
| [   78.529583][   T69] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/69
| [   78.529858][   T69]
[   78.529986][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   78.529989][   T69] Workqueue: netns cleanup_net
[   78.530010][   T69] Call Trace:
[   78.530017][   T69]  <TASK>
[   78.530019][   T69]  dump_stack_lvl (lib/dump_stack.c:123)
[   78.530039][   T69]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   78.530042][   T69]  kasan_report (mm/kasan/report.c:597)
[   78.530059][   T69]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   78.530064][   T69]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   78.530067][   T69]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   78.530072][   T69]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   78.530075][   T69]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   78.530080][   T69]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   78.530084][   T69]  __cancel_work_sync (kernel/workqueue.c:4383)
[   78.530088][   T69]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   78.530095][   T69]  ? netdev_notify_peers (net/core/dev.c:1891)
[   78.530098][   T69]  ? netif_close_many (net/core/dev.c:1959)
[   78.530103][   T69]  netif_close_many (net/core/dev.c:1959)
[   78.530106][   T69]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   78.530113][   T69]  ? __dev_close_many (net/core/dev.c:1949)
[   78.530117][   T69]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   78.530123][   T69]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   78.530130][   T69]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[   78.530137][   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)
[   78.530140][   T69]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   78.530146][   T69]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   78.530149][   T69]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   78.530152][   T69]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   78.530156][   T69]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   78.530163][   T69]  default_device_exit_batch (net/core/dev.c:13229)
[   78.530167][   T69]  ? unregister_netdev (net/core/dev.c:13204)
[   78.530173][   T69]  ops_undo_list (net/core/net_namespace.c:251)
[   78.530177][   T69]  ? netns_get (net/core/net_namespace.c:223)
[   78.530179][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   78.530184][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   78.530187][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   78.530191][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   78.530201][   T69]  process_one_work (kernel/workqueue.c:3268)
[   78.530207][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   78.530212][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   78.530216][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   78.530221][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   78.530224][   T69]  kthread (kernel/kthread.c:463)
[   78.530230][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   78.530232][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   78.530252][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   78.530256][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   78.530259][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   78.530262][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   78.530265][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   78.530268][   T69]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   78.540593][   T69] #PF: error_code(0x0002) - not-present page
| [   78.540804][   T69] PGD 0 P4D 0
| [   78.540963][   T69] Oops: Oops: 0002 [#1] SMP KASAN
| [   78.541533][   T69] Tainted: [B]=BAD_PAGE
[   78.541669][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   78.541887][   T69] Workqueue: netns cleanup_net
[   78.542080][   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)
[   78.542298][   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 7f 7f 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 7f 7f 81 00       	call   0x817fa9
  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
[   78.542920][   T69] RSP: 0018:ffffc900004a7690 EFLAGS: 00010046
[   78.543146][   T69] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffb523f90a
[   78.543402][   T69] RDX: fffffbfff728b6cd RSI: 0000000000000008 RDI: ffffffffb945b660
[   78.543669][   T69] RBP: ffffc900004a76f8 R08: 0000000000000001 R09: fffffbfff728b6cc
[   78.543954][   T69] R10: ffffffffb945b667 R11: ffffc900004a7180 R12: 0000000000000000
[   78.544217][   T69] R13: 0000000000000286 R14: ffff88800be54000 R15: dffffc0000000000
[   78.544476][   T69] FS:  0000000000000000(0000) GS:ffff888077310000(0000) knlGS:0000000000000000
[   78.544784][   T69] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   78.545020][   T69] CR2: 0000000000000000 CR3: 0000000034735003 CR4: 0000000000772ef0
[   78.545277][   T69] PKRU: 55555554
[   78.545408][   T69] Call Trace:
[   78.545543][   T69]  <TASK>
[   78.545643][   T69]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   78.545819][   T69]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   78.546009][   T69]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   78.546180][   T69]  __cancel_work_sync (kernel/workqueue.c:4383)
[   78.546349][   T69]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   78.546527][   T69]  ? netdev_notify_peers (net/core/dev.c:1891)
[   78.546700][   T69]  ? netif_close_many (net/core/dev.c:1959)
[   78.546875][   T69]  netif_close_many (net/core/dev.c:1959)
[   78.547058][   T69]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   78.547228][   T69]  ? __dev_close_many (net/core/dev.c:1949)
[   78.547399][   T69]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   78.547618][   T69]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   78.547832][   T69]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[   78.548026][   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)
[   78.548196][   T69]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   78.548366][   T69]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   78.548541][   T69]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   78.548754][   T69]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   78.548938][   T69]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   78.549117][   T69]  default_device_exit_batch (net/core/dev.c:13229)
[   78.549286][   T69]  ? unregister_netdev (net/core/dev.c:13204)
[   78.549458][   T69]  ops_undo_list (net/core/net_namespace.c:251)
[   78.549633][   T69]  ? netns_get (net/core/net_namespace.c:223)
[   78.549803][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   78.549992][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   78.550164][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   78.550336][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   78.550516][   T69]  process_one_work (kernel/workqueue.c:3268)
[   78.550689][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   78.550869][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   78.551051][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   78.551225][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   78.551397][   T69]  kthread (kernel/kthread.c:463)
[   78.551535][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   78.551705][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   78.551883][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   78.552067][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   78.552238][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   78.552406][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   78.552583][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)


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