======================================
| [   27.017845][   T69] ==================================================================
| [   27.018194][   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)
| [   27.018501][   T69] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/69
| [   27.018805][   T69]
[   27.018917][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   27.018919][   T69] Workqueue: netns cleanup_net
[   27.018926][   T69] Call Trace:
[   27.018928][   T69]  <TASK>
[   27.018930][   T69]  dump_stack_lvl (lib/dump_stack.c:123)
[   27.018936][   T69]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   27.018940][   T69]  kasan_report (mm/kasan/report.c:597)
[   27.018946][   T69]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   27.018951][   T69]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   27.018955][   T69]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   27.018959][   T69]  ? irqentry_exit (kernel/entry/common.c:215)
[   27.018964][   T69]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   27.018967][   T69]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   27.018973][   T69]  ? queue_delayed_work_on (kernel/workqueue.c:2567)
[   27.018977][   T69]  __cancel_work_sync (kernel/workqueue.c:4383)
[   27.018982][   T69]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   27.018987][   T69]  ? netdev_notify_peers (net/core/dev.c:1891)
[   27.018992][   T69]  ? netif_close_many (net/core/dev.c:1959)
[   27.018997][   T69]  netif_close_many (net/core/dev.c:1959)
[   27.019000][   T69]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   27.019006][   T69]  ? __dev_close_many (net/core/dev.c:1949)
[   27.019010][   T69]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   27.019015][   T69]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   27.019019][   T69]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[   27.019022][   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)
[   27.019026][   T69]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   27.019029][   T69]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   27.019031][   T69]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   27.019034][   T69]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   27.019037][   T69]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   27.019042][   T69]  default_device_exit_batch (net/core/dev.c:13229)
[   27.019046][   T69]  ? unregister_netdev (net/core/dev.c:13204)
[   27.019051][   T69]  ops_undo_list (net/core/net_namespace.c:251)
[   27.019056][   T69]  ? netns_get (net/core/net_namespace.c:223)
[   27.019059][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   27.019065][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   27.019068][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   27.019073][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   27.019079][   T69]  process_one_work (kernel/workqueue.c:3268)
[   27.019086][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   27.019092][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   27.019096][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   27.019103][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   27.019107][   T69]  kthread (kernel/kthread.c:463)
[   27.019111][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   27.019114][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   27.019118][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   27.019122][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   27.019125][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   27.019129][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   27.019132][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   27.019135][   T69]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   27.030916][   T69] #PF: error_code(0x0002) - not-present page
| [   27.031159][   T69] PGD 0 P4D 0
| [   27.031311][   T69] Oops: Oops: 0002 [#1] SMP KASAN
| [   27.031955][   T69] Tainted: [B]=BAD_PAGE
[   27.032106][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   27.032355][   T69] Workqueue: netns cleanup_net
[   27.032564][   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)
[   27.032821][   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
[   27.033516][   T69] RSP: 0018:ffffc900004a7690 EFLAGS: 00010046
[   27.033762][   T69] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8d84190a
[   27.034057][   T69] RDX: fffffbfff239cecd RSI: 0000000000000008 RDI: ffffffff91ce7660
[   27.034349][   T69] RBP: ffffc900004a76f8 R08: 0000000000000001 R09: fffffbfff239cecc
[   27.034645][   T69] R10: ffffffff91ce7667 R11: ffffc900004a7180 R12: 0000000000000000
[   27.034938][   T69] R13: 0000000000000286 R14: ffff8880027dc000 R15: dffffc0000000000
[   27.035233][   T69] FS:  0000000000000000(0000) GS:ffff8880a4604000(0000) knlGS:0000000000000000
[   27.035574][   T69] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   27.035821][   T69] CR2: 0000000000000000 CR3: 0000000016b59006 CR4: 0000000000772ef0
[   27.036116][   T69] PKRU: 55555554
[   27.036265][   T69] Call Trace:
[   27.036414][   T69]  <TASK>
[   27.036515][   T69]  ? irqentry_exit (kernel/entry/common.c:215)
[   27.036717][   T69]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   27.036915][   T69]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   27.037112][   T69]  ? queue_delayed_work_on (kernel/workqueue.c:2567)
[   27.037311][   T69]  __cancel_work_sync (kernel/workqueue.c:4383)
[   27.037508][   T69]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   27.037706][   T69]  ? netdev_notify_peers (net/core/dev.c:1891)
[   27.037903][   T69]  ? netif_close_many (net/core/dev.c:1959)
[   27.038101][   T69]  netif_close_many (net/core/dev.c:1959)
[   27.038297][   T69]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   27.038497][   T69]  ? __dev_close_many (net/core/dev.c:1949)
[   27.038693][   T69]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   27.038940][   T69]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   27.039189][   T69]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[   27.039386][   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)
[   27.039581][   T69]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   27.039776][   T69]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   27.039972][   T69]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   27.040216][   T69]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   27.040422][   T69]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   27.040625][   T69]  default_device_exit_batch (net/core/dev.c:13229)
[   27.040823][   T69]  ? unregister_netdev (net/core/dev.c:13204)
[   27.041021][   T69]  ops_undo_list (net/core/net_namespace.c:251)
[   27.041220][   T69]  ? netns_get (net/core/net_namespace.c:223)
[   27.041415][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   27.041615][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   27.041811][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   27.042013][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   27.042212][   T69]  process_one_work (kernel/workqueue.c:3268)
[   27.042412][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   27.042609][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   27.042808][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   27.043007][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   27.043204][   T69]  kthread (kernel/kthread.c:463)
[   27.043354][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   27.043554][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   27.043750][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   27.043947][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   27.044145][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   27.044342][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   27.044537][   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