======================================
| [  100.315491][   T71] ==================================================================
| [  100.315818][   T71] 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)
| [  100.316109][   T71] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/71
| [  100.316400][   T71]
[  100.316504][   T71] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  100.316508][   T71] Workqueue: netns cleanup_net
[  100.316518][   T71] Call Trace:
[  100.316520][   T71]  <TASK>
[  100.316523][   T71]  dump_stack_lvl (lib/dump_stack.c:123)
[  100.316535][   T71]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  100.316538][   T71]  kasan_report (mm/kasan/report.c:597)
[  100.316546][   T71]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  100.316551][   T71]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[  100.316555][   T71]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  100.316560][   T71]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[  100.316564][   T71]  ? enable_delayed_work (kernel/workqueue.c:4359)
[  100.316569][   T71]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[  100.316574][   T71]  __cancel_work_sync (kernel/workqueue.c:4383)
[  100.316578][   T71]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[  100.316587][   T71]  ? netdev_notify_peers (net/core/dev.c:1891)
[  100.316591][   T71]  ? netif_close_many (net/core/dev.c:1959)
[  100.316598][   T71]  netif_close_many (net/core/dev.c:1959)
[  100.316602][   T71]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[  100.316609][   T71]  ? __dev_close_many (net/core/dev.c:1949)
[  100.316613][   T71]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[  100.316618][   T71]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[  100.316622][   T71]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[  100.316627][   T71]  ? 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)
[  100.316630][   T71]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[  100.316633][   T71]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  100.316636][   T71]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[  100.316639][   T71]  ? unregister_netdevice_many (net/core/dev.c:12441)
[  100.316642][   T71]  ? unregister_netdevice_many (net/core/dev.c:12441)
[  100.316647][   T71]  default_device_exit_batch (net/core/dev.c:13229)
[  100.316651][   T71]  ? unregister_netdev (net/core/dev.c:13204)
[  100.316656][   T71]  ops_undo_list (net/core/net_namespace.c:251)
[  100.316661][   T71]  ? netns_get (net/core/net_namespace.c:223)
[  100.316664][   T71]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  100.316670][   T71]  cleanup_net (net/core/net_namespace.c:698)
[  100.316673][   T71]  ? net_passive_dec (net/core/net_namespace.c:660)
[  100.316678][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  100.316686][   T71]  process_one_work (kernel/workqueue.c:3268)
[  100.316693][   T71]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  100.316700][   T71]  ? assign_work (kernel/workqueue.c:1206)
[  100.316705][   T71]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  100.316711][   T71]  ? rescuer_thread (kernel/workqueue.c:3373)
[  100.316715][   T71]  kthread (kernel/kthread.c:463)
[  100.316720][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  100.316723][   T71]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  100.316728][   T71]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  100.316731][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  100.316735][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  100.316738][   T71]  ret_from_fork (arch/x86/kernel/process.c:164)
[  100.316741][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  100.316744][   T71]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [  100.327744][   T71] #PF: error_code(0x0002) - not-present page
| [  100.328052][   T71] PGD 0 P4D 0
| [  100.328189][   T71] Oops: Oops: 0002 [#1] SMP KASAN
| [  100.328861][   T71] Tainted: [B]=BAD_PAGE
[  100.328993][   T71] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  100.329216][   T71] Workqueue: netns cleanup_net
[  100.329404][   T71] 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)
[  100.329733][   T71] 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
[  100.330455][   T71] RSP: 0018:ffffc900004c7690 EFLAGS: 00010046
[  100.330678][   T71] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffabc4190a
[  100.330940][   T71] RDX: fffffbfff601cecd RSI: 0000000000000008 RDI: ffffffffb00e7660
[  100.331305][   T71] RBP: ffffc900004c76f8 R08: 0000000000000001 R09: fffffbfff601cecc
[  100.331566][   T71] R10: ffffffffb00e7667 R11: ffffc900004c7180 R12: 0000000000000000
[  100.331830][   T71] R13: 0000000000000286 R14: ffff888005464000 R15: dffffc0000000000
[  100.332207][   T71] FS:  0000000000000000(0000) GS:ffff888086184000(0000) knlGS:0000000000000000
[  100.332514][   T71] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  100.332831][   T71] CR2: 0000000000000000 CR3: 000000000f656002 CR4: 0000000000772ef0
[  100.333102][   T71] PKRU: 55555554
[  100.333236][   T71] Call Trace:
[  100.333372][   T71]  <TASK>
[  100.333479][   T71]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[  100.333760][   T71]  ? enable_delayed_work (kernel/workqueue.c:4359)
[  100.333938][   T71]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[  100.334114][   T71]  __cancel_work_sync (kernel/workqueue.c:4383)
[  100.334287][   T71]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[  100.334560][   T71]  ? netdev_notify_peers (net/core/dev.c:1891)
[  100.334736][   T71]  ? netif_close_many (net/core/dev.c:1959)
[  100.334919][   T71]  netif_close_many (net/core/dev.c:1959)
[  100.335093][   T71]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[  100.335365][   T71]  ? __dev_close_many (net/core/dev.c:1949)
[  100.335541][   T71]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[  100.335758][   T71]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[  100.336068][   T71]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[  100.336240][   T71]  ? 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)
[  100.336414][   T71]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[  100.336590][   T71]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  100.336885][   T71]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[  100.337101][   T71]  ? unregister_netdevice_many (net/core/dev.c:12441)
[  100.337273][   T71]  ? unregister_netdevice_many (net/core/dev.c:12441)
[  100.337458][   T71]  default_device_exit_batch (net/core/dev.c:13229)
[  100.337729][   T71]  ? unregister_netdev (net/core/dev.c:13204)
[  100.337915][   T71]  ops_undo_list (net/core/net_namespace.c:251)
[  100.338102][   T71]  ? netns_get (net/core/net_namespace.c:223)
[  100.338276][   T71]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  100.338550][   T71]  cleanup_net (net/core/net_namespace.c:698)
[  100.338725][   T71]  ? net_passive_dec (net/core/net_namespace.c:660)
[  100.338897][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  100.339073][   T71]  process_one_work (kernel/workqueue.c:3268)
[  100.339344][   T71]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  100.339520][   T71]  ? assign_work (kernel/workqueue.c:1206)
[  100.339699][   T71]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  100.339874][   T71]  ? rescuer_thread (kernel/workqueue.c:3373)
[  100.340144][   T71]  kthread (kernel/kthread.c:463)
[  100.340289][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  100.340462][   T71]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  100.340636][   T71]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  100.340903][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  100.341084][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  100.341263][   T71]  ret_from_fork (arch/x86/kernel/process.c:164)
[  100.341434][   T71]  ? 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