unregister_netdevice: waiting for lo to become free. Usage count = 4
unregister_netdevice: waiting for lo to become free. Usage count = 4
unregister_netdevice: waiting for lo to become free. Usage count = 4
unregister_netdevice: waiting for lo to become free. Usage count = 4
unregister_netdevice: waiting for lo to become free. Usage count = 4
INFO: task syz-executor0:25600 blocked for more than 120 seconds.
      Not tainted 4.9.93-gf6bec4e #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D28760 25600      1 0x00000004
 ffff8801ca5a8000 ffff8801c04279c0 ffff8801b9465500 ffff8801ab854800
 ffff8801db321b98 ffff8801b7057bc8 ffffffff838c4a7d ffff8801ca5a88c0
 ffffed00394b5117 ffff8801ca5a8000 00fffc0000000000 ffff8801db322468
Call Trace:
 [<ffffffff838c607f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3556
 [<ffffffff838c6a03>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3589
 [<ffffffff838cae86>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff838cae86>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff82f39e15>] copy_net_ns+0x155/0x290 net/core/net_namespace.c:387
 [<ffffffff8119e1bc>] create_new_namespaces+0x51c/0x730 kernel/nsproxy.c:106
 [<ffffffff8119e9b5>] unshare_nsproxy_namespaces+0xa5/0x1d0 kernel/nsproxy.c:205
 [<ffffffff81133289>] SYSC_unshare kernel/fork.c:2244 [inline]
 [<ffffffff81133289>] SyS_unshare+0x319/0x710 kernel/fork.c:2194
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff838d5953>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/515:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813643dc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813643dc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81423b90>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3649:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d560c>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3745:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838d3b22>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82007e22>] n_tty_read+0x202/0x16b0 drivers/tty/n_tty.c:2133
3 locks held by kworker/u4:5/12290:
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118ab9e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118ab9e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118ab9e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118ab9e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  (net_cleanup_work){+.+.+.}, at: [<ffffffff8118abd8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 #2:  (net_mutex){+.+.+.}, at: [<ffffffff82f397cf>] cleanup_net+0x13f/0x630 net/core/net_namespace.c:420
1 lock held by syz-executor0/25600:
 #0:  (net_mutex){+.+.+.}, at: [<ffffffff82f39e15>] copy_net_ns+0x155/0x290 net/core/net_namespace.c:387

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 515 Comm: khungtaskd Not tainted 4.9.93-gf6bec4e #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d866fd08 ffffffff81d9c299 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b7d90 ffff8801d866fd40
 ffffffff81da75d7 0000000000000001 0000000000000000 0000000000000002
Call Trace:
 [<ffffffff81d9c299>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d9c299>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81da75d7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81da756a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b7e94>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81364974>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81364974>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81364974>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81364974>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119ab4d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838d5b1c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 3647 Comm: rs:main Q:Reg Not tainted 4.9.93-gf6bec4e #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801ba961800 task.stack: ffff8801b9d08000
RIP: 0010:[<ffffffff81231e94>] 
c [<ffffffff81231e94>] mark_lock+0xc4/0x1280 kernel/locking/lockdep.c:3092
RSP: 0018:ffff8801b9d0f310  EFLAGS: 00000082
RAX: 0000000000000001 RBX: ffff8801ba962160 RCX: 1ffff1003752c430
RDX: 1ffffffff0a77188 RSI: ffff8801ba962160 RDI: ffffffff853b8c40
RBP: ffff8801b9d0f338 R08: ffff8801ba962180 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff853b8c10
R13: 0000000000000001 R14: 0000000000000007 R15: ffff8801ba961800
FS:  00007fc5a463d700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f331bd5c000 CR3: 00000001be1f4000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000004
c ffff8801ba9620c0
c ffffed003752c417
c ffff8801ba961800
c
 dffffc0000000000
c ffff8801b9d0f388
c ffffffff81233117
c 0000000000000006
c
 ffff8801ba9620b8
c 0000000600000007
c ffff8801ba961800
c ffffffff81539859
c
Call Trace:
 [<ffffffff81233117>] mark_held_locks+0xc7/0x130 kernel/locking/lockdep.c:2660
 [<ffffffff8123350b>] __trace_hardirqs_on_caller kernel/locking/lockdep.c:2689 [inline]
 [<ffffffff8123350b>] trace_hardirqs_on_caller+0x38b/0x590 kernel/locking/lockdep.c:2736
 [<ffffffff8123371d>] trace_hardirqs_on+0xd/0x10 kernel/locking/lockdep.c:2743
 [<ffffffff81539859>] quarantine_put+0xd9/0x180 mm/kasan/quarantine.c:209
 [<ffffffff81538da8>] kasan_slab_free+0x88/0xc0 mm/kasan/kasan.c:583
 [<ffffffff81535a8e>] slab_free_hook mm/slub.c:1355 [inline]
 [<ffffffff81535a8e>] slab_free_freelist_hook mm/slub.c:1377 [inline]
 [<ffffffff81535a8e>] slab_free mm/slub.c:2958 [inline]
 [<ffffffff81535a8e>] kmem_cache_free+0xbe/0x310 mm/slub.c:2980
 [<ffffffff81831f84>] ext4_es_free_extent+0x214/0x470 fs/ext4/extents_status.c:370
 [<ffffffff81834981>] __es_remove_extent+0x511/0x830 fs/ext4/extents_status.c:915
 [<ffffffff81836d45>] ext4_es_remove_extent+0xa5/0x310 fs/ext4/extents_status.c:966
 [<ffffffff817f481c>] ext4_ext_truncate+0x15c/0x280 fs/ext4/extents.c:4647
 [<ffffffff81749ec5>] ext4_truncate+0xa15/0x12c0 fs/ext4/inode.c:4260
 [<ffffffff8174c05b>] ext4_truncate_failed_write fs/ext4/truncate.h:15 [inline]
 [<ffffffff8174c05b>] ext4_da_write_begin+0x4eb/0x1020 fs/ext4/inode.c:3015
 [<ffffffff81433bc1>] generic_perform_write+0x301/0x510 mm/filemap.c:2741
 [<ffffffff8143b642>] __generic_file_write_iter+0x352/0x540 mm/filemap.c:2866
 [<ffffffff817222b3>] ext4_file_write_iter+0x463/0xd90 fs/ext4/file.c:165
 [<ffffffff8156c430>] new_sync_write fs/read_write.c:496 [inline]
 [<ffffffff8156c430>] __vfs_write+0x3e0/0x580 fs/read_write.c:509
 [<ffffffff81570227>] vfs_write+0x187/0x530 fs/read_write.c:557
 [<ffffffff81574059>] SYSC_write fs/read_write.c:604 [inline]
 [<ffffffff81574059>] SyS_write+0xd9/0x1c0 fs/read_write.c:596
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff838d5953>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
c00 
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c00 
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c48 
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c<5b> 
c41 
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c48 
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c00 
c