======================================
| [   38.698794][   T70] ==================================================================
| [   38.699291][   T70] 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)
| [   38.699745][   T70] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/70
| [   38.700160][   T70]
[   38.700323][   T70] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   38.700327][   T70] Workqueue: netns cleanup_net
[   38.700347][   T70] Call Trace:
[   38.700350][   T70]  <TASK>
[   38.700353][   T70]  dump_stack_lvl (lib/dump_stack.c:123)
[   38.700364][   T70]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   38.700370][   T70]  kasan_report (mm/kasan/report.c:597)
[   38.700383][   T70]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   38.700392][   T70]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   38.700399][   T70]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   38.700404][   T70]  ? irqentry_exit (kernel/entry/common.c:215)
[   38.700414][   T70]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   38.700418][   T70]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   38.700428][   T70]  ? queue_delayed_work_on (kernel/workqueue.c:2567)
[   38.700436][   T70]  __cancel_work_sync (kernel/workqueue.c:4383)
[   38.700443][   T70]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   38.700452][   T70]  ? netdev_notify_peers (net/core/dev.c:1891)
[   38.700459][   T70]  ? netif_close_many (net/core/dev.c:1959)
[   38.700468][   T70]  netif_close_many (net/core/dev.c:1959)
[   38.700473][   T70]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   38.700485][   T70]  ? __dev_close_many (net/core/dev.c:1949)
[   38.700492][   T70]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   38.700497][   T70]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   38.700505][   T70]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   38.700514][   T70]  ? default_device_exit_batch (net/core/dev.c:13215)
[   38.700523][   T70]  ? 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)
[   38.700529][   T70]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   38.700534][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   38.700540][   T70]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   38.700545][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   38.700551][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   38.700563][   T70]  default_device_exit_batch (net/core/dev.c:13229)
[   38.700570][   T70]  ? unregister_netdev (net/core/dev.c:13204)
[   38.700582][   T70]  ops_undo_list (net/core/net_namespace.c:251)
[   38.700592][   T70]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   38.700597][   T70]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   38.700609][   T70]  cleanup_net (net/core/net_namespace.c:698)
[   38.700616][   T70]  ? net_passive_dec (net/core/net_namespace.c:660)
[   38.700625][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   38.700636][   T70]  process_one_work (kernel/workqueue.c:3268)
[   38.700649][   T70]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   38.700661][   T70]  ? assign_work (kernel/workqueue.c:1206)
[   38.700669][   T70]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   38.700681][   T70]  ? rescuer_thread (kernel/workqueue.c:3373)
[   38.700688][   T70]  kthread (kernel/kthread.c:463)
[   38.700696][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   38.700701][   T70]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   38.700716][   T70]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   38.700723][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   38.700729][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   38.700736][   T70]  ret_from_fork (arch/x86/kernel/process.c:164)
[   38.700741][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   38.700746][   T70]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   38.716135][   T70] #PF: error_code(0x0002) - not-present page
| [   38.716347][   T70] PGD 0 P4D 0
| [   38.716483][   T70] Oops: Oops: 0002 [#1] SMP KASAN
| [   38.717065][   T70] Tainted: [B]=BAD_PAGE
[   38.717191][   T70] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   38.717404][   T70] Workqueue: netns cleanup_net
[   38.717597][   T70] 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)
[   38.717821][   T70] 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 1f 93 82 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 1f 93 82 00       	call   0x829349
  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
[   38.718416][   T70] RSP: 0018:ffffc900004b7680 EFLAGS: 00010046
[   38.718628][   T70] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffb6a49b8a
[   38.718912][   T70] RDX: fffffbfff76ecacd RSI: 0000000000000008 RDI: ffffffffbb765660
[   38.719168][   T70] RBP: ffffc900004b76e8 R08: 0000000000000001 R09: fffffbfff76ecacc
[   38.719437][   T70] R10: ffffffffbb765667 R11: ffffc900004b7140 R12: 0000000000000000
[   38.719709][   T70] R13: 0000000000000282 R14: ffff8880104f9000 R15: dffffc0000000000
[   38.719964][   T70] FS:  0000000000000000(0000) GS:ffff8880b1907000(0000) knlGS:0000000000000000
[   38.720252][   T70] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   38.720462][   T70] CR2: 0000000000000000 CR3: 0000000020749001 CR4: 0000000000772ef0
[   38.720711][   T70] PKRU: 55555554
[   38.720838][   T70] Call Trace:
[   38.720966][   T70]  <TASK>
[   38.721055][   T70]  ? irqentry_exit (kernel/entry/common.c:215)
[   38.721231][   T70]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   38.721401][   T70]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   38.721570][   T70]  ? queue_delayed_work_on (kernel/workqueue.c:2567)
[   38.721737][   T70]  __cancel_work_sync (kernel/workqueue.c:4383)
[   38.721902][   T70]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   38.722088][   T70]  ? netdev_notify_peers (net/core/dev.c:1891)
[   38.722258][   T70]  ? netif_close_many (net/core/dev.c:1959)
[   38.722430][   T70]  netif_close_many (net/core/dev.c:1959)
[   38.722594][   T70]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   38.722776][   T70]  ? __dev_close_many (net/core/dev.c:1949)
[   38.722936][   T70]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   38.723139][   T70]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   38.723304][   T70]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   38.723523][   T70]  ? default_device_exit_batch (net/core/dev.c:13215)
[   38.723689][   T70]  ? 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)
[   38.723868][   T70]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   38.724030][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   38.724196][   T70]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   38.724400][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   38.724565][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   38.724738][   T70]  default_device_exit_batch (net/core/dev.c:13229)
[   38.724898][   T70]  ? unregister_netdev (net/core/dev.c:13204)
[   38.725065][   T70]  ops_undo_list (net/core/net_namespace.c:251)
[   38.725231][   T70]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   38.725398][   T70]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   38.725566][   T70]  cleanup_net (net/core/net_namespace.c:698)
[   38.725736][   T70]  ? net_passive_dec (net/core/net_namespace.c:660)
[   38.725901][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   38.726072][   T70]  process_one_work (kernel/workqueue.c:3268)
[   38.726239][   T70]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   38.726503][   T70]  ? assign_work (kernel/workqueue.c:1206)
[   38.726672][   T70]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   38.726835][   T70]  ? rescuer_thread (kernel/workqueue.c:3373)
[   38.726997][   T70]  kthread (kernel/kthread.c:463)
[   38.727123][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   38.727384][   T70]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   38.727563][   T70]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   38.727727][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   38.727887][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   38.728146][   T70]  ret_from_fork (arch/x86/kernel/process.c:164)
[   38.728307][   T70]  ? 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