** the kernel, report this immediately to your vendor!  **
**                                                      **
**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **
**********************************************************
======================================================
WARNING: possible circular locking dependency detected
4.19.195-syzkaller #0 Not tainted
------------------------------------------------------
kworker/u4:5/9508 is trying to acquire lock:
0000000093ad13b3 ((wq_completion)"events"){+.+.}, at: flush_workqueue+0xe8/0x13e0 kernel/workqueue.c:2658

but task is already holding lock:
000000003fa8f7c2 (pernet_ops_rwsem){++++}, at: cleanup_net+0xa8/0x8b0 net/core/net_namespace.c:520

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (pernet_ops_rwsem){++++}:
       unregister_netdevice_notifier+0x7b/0x330 net/core/dev.c:1708
       raw_release+0x58/0x820 net/can/raw.c:358
       __sock_release+0xcd/0x2a0 net/socket.c:579
       sock_close+0x15/0x20 net/socket.c:1140
       __fput+0x2ce/0x890 fs/file_table.c:278
       task_work_run+0x148/0x1c0 kernel/task_work.c:113
       tracehook_notify_resume include/linux/tracehook.h:193 [inline]
       exit_to_usermode_loop+0x251/0x2a0 arch/x86/entry/common.c:167
       prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
       syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
       do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #2 (&sb->s_type->i_mutex_key#13){+.+.}:
       inode_lock include/linux/fs.h:748 [inline]
       __sock_release+0x86/0x2a0 net/socket.c:578
       sock_close+0x15/0x20 net/socket.c:1140
vhci_hcd vhci_hcd.0: pdev(5) rhport(1) sockfd(3)
       __fput+0x2ce/0x890 fs/file_table.c:278
vhci_hcd vhci_hcd.0: devid(0) speed(3) speed_str(high-speed)
       delayed_fput+0x56/0x70 fs/file_table.c:304
       process_one_work+0x864/0x1570 kernel/workqueue.c:2153
       worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
vhci_hcd vhci_hcd.0: Device attached
       kthread+0x33f/0x460 kernel/kthread.c:259
       ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

-> #1 ((delayed_fput_work).work){+.+.}:
vhci_hcd: connection closed
vhci_hcd: stop threads
       worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
       kthread+0x33f/0x460 kernel/kthread.c:259
       ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

-> #0 ((wq_completion)"events"){+.+.}:
       flush_workqueue+0x117/0x13e0 kernel/workqueue.c:2661
       flush_scheduled_work include/linux/workqueue.h:599 [inline]
       tipc_exit_net+0x38/0x60 net/tipc/core.c:100
       ops_exit_list+0xa5/0x150 net/core/net_namespace.c:153
vhci_hcd: release socket
       cleanup_net+0x3b4/0x8b0 net/core/net_namespace.c:553
       process_one_work+0x864/0x1570 kernel/workqueue.c:2153
       worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
       kthread+0x33f/0x460 kernel/kthread.c:259
       ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

other info that might help us debug this:

Chain exists of:
  (wq_completion)"events" --> &sb->s_type->i_mutex_key#13 --> pernet_ops_rwsem

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(pernet_ops_rwsem);
vhci_hcd: disconnect device
                               lock(&sb->s_type->i_mutex_key#13);
                               lock(pernet_ops_rwsem);
  lock((wq_completion)"events");

 *** DEADLOCK ***

3 locks held by kworker/u4:5/9508:
 #0: 00000000ce82b47a ((wq_completion)"%s""netns"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2124
 #1: 000000009c29c7ce (net_cleanup_work){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2128
 #2: 000000003fa8f7c2 (pernet_ops_rwsem){++++}, at: cleanup_net+0xa8/0x8b0 net/core/net_namespace.c:520

stack backtrace:
CPU: 0 PID: 9508 Comm: kworker/u4:5 Not tainted 4.19.195-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
 print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1222
 check_prev_add kernel/locking/lockdep.c:1866 [inline]
 check_prevs_add kernel/locking/lockdep.c:1979 [inline]
 validate_chain kernel/locking/lockdep.c:2420 [inline]
 __lock_acquire+0x30c9/0x3ff0 kernel/locking/lockdep.c:3416
 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
 flush_workqueue+0x117/0x13e0 kernel/workqueue.c:2661
 flush_scheduled_work include/linux/workqueue.h:599 [inline]
 tipc_exit_net+0x38/0x60 net/tipc/core.c:100
 ops_exit_list+0xa5/0x150 net/core/net_namespace.c:153
 cleanup_net+0x3b4/0x8b0 net/core/net_namespace.c:553
 process_one_work+0x864/0x1570 kernel/workqueue.c:2153
 worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
 kthread+0x33f/0x460 kernel/kthread.c:259
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Cannot find del_set index 65534 as target
IPVS: ftp: loaded support on port[0] = 21
Cannot find del_set index 65534 as target
vhci_hcd vhci_hcd.0: pdev(5) rhport(0) sockfd(5)
vhci_hcd vhci_hcd.0: devid(0) speed(3) speed_str(high-speed)
vhci_hcd vhci_hcd.0: Device attached
vhci_hcd: connection closed
vhci_hcd: stop threads
vhci_hcd: release socket
IPVS: ftp: loaded support on port[0] = 21
vhci_hcd: disconnect device
tmpfs: Bad value 'prefer=relative:' for mount option 'mpol'
ieee802154 phy0 wpan0: encryption failed: -22
ieee802154 phy1 wpan1: encryption failed: -22