unregister_netdevice: waiting for lo to become free. Usage count = 2
INFO: task syz-executor7:8832 blocked for more than 120 seconds.
      Not tainted 4.9.40-ged32335 #11
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor7   D28896  8832  24902 0x00000004
 ffff8801c7bc0000 ffff8801cd4bef40 ffff8801ca2e8540 ffff8801d9884680
 ffff8801db221498 ffff8801c7bcf9f8 ffffffff8388f2bb 0000000000000000
 0000000000000007 00ff8801c7bc0000 ffff8801db221db0 ffff8801db221dd8
Call Trace:
 [<ffffffff83890872>] schedule+0x92/0x1b0 kernel/sched/core.c:3624
 [<ffffffff838911e3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3657
 [<ffffffff838967f2>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff838967f2>] mutex_lock_nested+0x312/0x870 kernel/locking/mutex.c:621
 [<ffffffff82f0bba5>] copy_net_ns+0x155/0x280 net/core/net_namespace.c:387
 [<ffffffff8119e31f>] create_new_namespaces+0x37f/0x730 kernel/nsproxy.c:106
 [<ffffffff8119e961>] copy_namespaces+0x291/0x320 kernel/nsproxy.c:164
 [<ffffffff8112b809>] copy_process.part.50+0x1c99/0x5d40 kernel/fork.c:1658
 [<ffffffff8112fd40>] copy_process kernel/fork.c:1482 [inline]
 [<ffffffff8112fd40>] _do_fork+0x1c0/0xd70 kernel/fork.c:1940
 [<ffffffff811309c7>] SYSC_clone kernel/fork.c:2050 [inline]
 [<ffffffff811309c7>] SyS_clone+0x37/0x50 kernel/fork.c:2044
 [<ffffffff81006527>] do_syscall_64+0x197/0x490 arch/x86/entry/common.c:280
 [<ffffffff838a078d>] entry_SYSCALL64_slow_path+0x25/0x25

Showing all locks held in the system:
2 locks held by khungtaskd/513:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136d275>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136d275>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81233524>] debug_show_all_locks+0x74/0x290 kernel/locking/lockdep.c:4329
2 locks held by getty/3214:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8389e8c2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81fff0f4>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
3 locks held by kworker/u4:4/3600:
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff81189e29>] __write_once_size include/linux/compiler.h:272 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff81189e29>] atomic64_set arch/x86/include/asm/atomic64_64.h:33 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff81189e29>] atomic_long_set include/asm-generic/atomic-long.h:56 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff81189e29>] set_work_data kernel/workqueue.c:615 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff81189e29>] set_work_pool_and_clear_pending kernel/workqueue.c:642 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff81189e29>] process_one_work+0x6a9/0x15f0 kernel/workqueue.c:2089
 #1:  (net_cleanup_work){+.+.+.}, at: [<ffffffff81189e5b>] process_one_work+0x6db/0x15f0 kernel/workqueue.c:2093
 #2:  (net_mutex){+.+.+.}, at: [<ffffffff82f0b57f>] cleanup_net+0x13f/0x610 net/core/net_namespace.c:420
1 lock held by syz-executor7/8832:
 #0:  (net_mutex){+.+.+.}, at: [<ffffffff82f0bba5>] copy_net_ns+0x155/0x280 net/core/net_namespace.c:387

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

NMI backtrace for cpu 1
CPU: 1 PID: 513 Comm: khungtaskd Not tainted 4.9.40-ged32335 #11
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8817d00 ffffffff81d8d829 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810bd010 ffff8801d8817d38
 ffffffff81d9893d 0000000000000001 0000000000000000 ffff8801c7bc0398
Call Trace:
 [<ffffffff81d8d829>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d8d829>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9893d>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d98a77>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810bd104>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff8136d840>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff8136d840>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8136d840>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8136d840>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff8119ad8d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838a096a>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.40-ged32335 #11
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff84426880 task.stack: ffffffff84400000
RIP: 0010:[<ffffffff8136e5f1>] 
c [<ffffffff8136e5f1>] touch_softlockup_watchdog_sched+0x1/0x20 kernel/watchdog.c:178
RSP: 0018:ffff8801db207f50  EFLAGS: 00000002
RAX: 0000000000000001 RBX: ffff8801db21a600 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff8801db21a600 RDI: ffffffff84a2b170
RBP: ffff8801db207f60 R08: ffff88021fffd01c R09: ffff88021fffd008
R10: ffff88021fffd018 R11: ffff88021fffd010 R12: 0000005571f0dae8
R13: ffff8801db21a690 R14: 0000005571f0dae8 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c4346bb704 CR3: 00000001d1ec3000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801db207f60
c ffffffff811debd7
c ffff8801db207f80
c ffffffff812d31eb
c
 ffff8801db21a600
c ffff8801db21a674
c ffff8801db207fb8
c ffffffff812d557e
c
 ffff8801db207fb8
c ffffffff84426880
c 0000000000000000
c 0000000000000000
c
Call Trace:
 [<ffffffff812d31eb>] tick_nohz_stop_idle+0x5b/0x70 kernel/time/tick-sched.c:558
 [<ffffffff812d557e>] tick_nohz_irq_enter kernel/time/tick-sched.c:1119 [inline]
 [<ffffffff812d557e>] tick_irq_enter+0x1be/0x220 kernel/time/tick-sched.c:1138
 [<ffffffff81147743>] irq_enter+0xb3/0xd0 kernel/softirq.c:345
 [<ffffffff810aec6a>] smp_reschedule_interrupt+0xa/0x80 arch/x86/kernel/smp.c:264
 [<ffffffff838a275c>] reschedule_interrupt+0x8c/0xa0 arch/x86/entry/entry_64.S:732
 <EOI> 
d [<ffffffff8389f336>] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
 [<ffffffff8389e965>] arch_safe_halt arch/x86/include/asm/paravirt.h:103 [inline]
 [<ffffffff8389e965>] default_idle+0x55/0x360 arch/x86/kernel/process.c:295
 [<ffffffff8106c35a>] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:286
 [<ffffffff8389f786>] default_idle_call+0x36/0x60 kernel/sched/idle.c:97
 [<ffffffff812263bc>] cpuidle_idle_call kernel/sched/idle.c:155 [inline]
 [<ffffffff812263bc>] cpu_idle_loop kernel/sched/idle.c:248 [inline]
 [<ffffffff812263bc>] cpu_startup_entry+0x30c/0x3d0 kernel/sched/idle.c:303
 [<ffffffff8388be94>] rest_init+0x184/0x190 init/main.c:408
 [<ffffffff84a638a7>] start_kernel+0x679/0x6ae init/main.c:662
 [<ffffffff84a6229d>] x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
 [<ffffffff84a623df>] x86_64_start_kernel+0x140/0x163 arch/x86/kernel/head64.c:177
Code: 
ce8 
c75 
c9a 
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c00 
ce9 
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cff 
cff 
cff 
c4c 
c89 
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c00 
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ce8 
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c9a 
c1c 
c00 
ce9 
c55 
cfe 
cff 
cff 
c66 
c90 
c66 
c2e 
c0f 
c1f 
c84 
c00 
c00 
c00 
c00 
c00 
c55 
c<48> 
c89 
ce5 
ce8 
c37 
c70 
cff 
cff 
c5d 
c65 
c48 
cc7 
c05 
c7a 
cc2 
cca 
c7e 
c00 
c00 
c00 
c00 
c