======================================================
WARNING: possible circular locking dependency detected
5.9.0-rc3-next-20200903-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.5/9413 is trying to acquire lock:
ffffffff8a87d730 (pernet_ops_rwsem){++++}-{3:3}, at: unregister_netdevice_notifier+0x1e/0x170 net/core/dev.c:1861

but task is already holding lock:
ffff88808d076c90 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:779 [inline]
ffff88808d076c90 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}, at: __sock_release+0x86/0x280 net/socket.c:595

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}:
       down_write+0x8d/0x150 kernel/locking/rwsem.c:1531
       inode_lock include/linux/fs.h:779 [inline]
       __sock_release+0x86/0x280 net/socket.c:595
       sock_close+0x18/0x20 net/socket.c:1277
       __fput+0x285/0x920 fs/file_table.c:281
       delayed_fput+0x56/0x70 fs/file_table.c:309
       process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
       worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
       kthread+0x3b5/0x4a0 kernel/kthread.c:292
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

-> #2 ((delayed_fput_work).work){+.+.}-{0:0}:
       process_one_work+0x8bb/0x1670 kernel/workqueue.c:2245
       worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
       kthread+0x3b5/0x4a0 kernel/kthread.c:292
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

-> #1 ((wq_completion)events){+.+.}-{0:0}:
       flush_workqueue+0x110/0x13e0 kernel/workqueue.c:2780
       flush_scheduled_work include/linux/workqueue.h:597 [inline]
       tipc_exit_net+0x47/0x2a0 net/tipc/core.c:116
       ops_exit_list+0xb0/0x160 net/core/net_namespace.c:186
       cleanup_net+0x4ea/0xb10 net/core/net_namespace.c:603
       process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
       worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
       kthread+0x3b5/0x4a0 kernel/kthread.c:292
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

-> #0 (pernet_ops_rwsem){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:2496 [inline]
       check_prevs_add kernel/locking/lockdep.c:2601 [inline]
       validate_chain kernel/locking/lockdep.c:3218 [inline]
       __lock_acquire+0x29bb/0x5570 kernel/locking/lockdep.c:4426
       lock_acquire+0x1f3/0xae0 kernel/locking/lockdep.c:5006
       down_write+0x8d/0x150 kernel/locking/rwsem.c:1531
       unregister_netdevice_notifier+0x1e/0x170 net/core/dev.c:1861
       raw_release+0x58/0x890 net/can/raw.c:354
       __sock_release+0xcd/0x280 net/socket.c:596
       sock_close+0x18/0x20 net/socket.c:1277
       __fput+0x285/0x920 fs/file_table.c:281
       task_work_run+0xdd/0x190 kernel/task_work.c:141
       exit_task_work include/linux/task_work.h:25 [inline]
       do_exit+0xb7d/0x29f0 kernel/exit.c:806
       do_group_exit+0x125/0x310 kernel/exit.c:903
       get_signal+0x428/0x1f00 kernel/signal.c:2757
       arch_do_signal+0x82/0x2520 arch/x86/kernel/signal.c:811
       exit_to_user_mode_loop kernel/entry/common.c:136 [inline]
       exit_to_user_mode_prepare+0x1ae/0x200 kernel/entry/common.c:167
       syscall_exit_to_user_mode+0x7e/0x2e0 kernel/entry/common.c:242
       entry_SYSCALL_64_after_hwframe+0x44/0xa9

other info that might help us debug this:

Chain exists of:
  pernet_ops_rwsem --> (delayed_fput_work).work --> &sb->s_type->i_mutex_key#12

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sb->s_type->i_mutex_key#12);
                               lock((delayed_fput_work).work);
                               lock(&sb->s_type->i_mutex_key#12);
  lock(pernet_ops_rwsem);

 *** DEADLOCK ***

1 lock held by syz-executor.5/9413:
 #0: ffff88808d076c90 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:779 [inline]
 #0: ffff88808d076c90 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}, at: __sock_release+0x86/0x280 net/socket.c:595

stack backtrace:
CPU: 0 PID: 9413 Comm: syz-executor.5 Not tainted 5.9.0-rc3-next-20200903-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fd lib/dump_stack.c:118
 check_noncircular+0x324/0x3e0 kernel/locking/lockdep.c:1827
 check_prev_add kernel/locking/lockdep.c:2496 [inline]
 check_prevs_add kernel/locking/lockdep.c:2601 [inline]
 validate_chain kernel/locking/lockdep.c:3218 [inline]
 __lock_acquire+0x29bb/0x5570 kernel/locking/lockdep.c:4426
 lock_acquire+0x1f3/0xae0 kernel/locking/lockdep.c:5006
 down_write+0x8d/0x150 kernel/locking/rwsem.c:1531
 unregister_netdevice_notifier+0x1e/0x170 net/core/dev.c:1861
 raw_release+0x58/0x890 net/can/raw.c:354
 __sock_release+0xcd/0x280 net/socket.c:596
 sock_close+0x18/0x20 net/socket.c:1277
 __fput+0x285/0x920 fs/file_table.c:281
 task_work_run+0xdd/0x190 kernel/task_work.c:141
 exit_task_work include/linux/task_work.h:25 [inline]
 do_exit+0xb7d/0x29f0 kernel/exit.c:806
 do_group_exit+0x125/0x310 kernel/exit.c:903
 get_signal+0x428/0x1f00 kernel/signal.c:2757
 arch_do_signal+0x82/0x2520 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:136 [inline]
 exit_to_user_mode_prepare+0x1ae/0x200 kernel/entry/common.c:167
 syscall_exit_to_user_mode+0x7e/0x2e0 kernel/entry/common.c:242
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45d5b9
Code: Bad RIP value.
RSP: 002b:00007f5ac6e5ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000029
RAX: 0000000000000004 RBX: 0000000000032bc0 RCX: 000000000045d5b9
RDX: 0000000000000001 RSI: 0000000000000003 RDI: 000000000000001d
RBP: 000000000118cf80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
R13: 00007ffd9f3b985f R14: 00007f5ac6e5b9c0 R15: 000000000118cf4c