unregister_netdevice: waiting for lo to become free. Usage count = 2
INFO: task syz-executor7:13256 blocked for more than 120 seconds.
      Not tainted 4.9.39-gf44842e #5
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor7   D28912 13256   3408 0x00000004
 ffff8801cd6ac680 ffff880197a92c00 ffff8801d1896e00 ffff8801c69e5e00
 ffff8801db321498 ffff8801d5c5fa18 ffffffff83954a3b 0000000000000000
 0000000000000007 00ff8801cd6ac680 ffff8801db321db0 ffff8801db321dd8
Call Trace:
 [<ffffffff83955ff2>] schedule+0x92/0x1b0 kernel/sched/core.c:3624
 [<ffffffff83956963>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3657
 [<ffffffff8395bcbf>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8395bcbf>] mutex_lock_nested+0x2ff/0x830 kernel/locking/mutex.c:621
 [<ffffffff82f413f5>] copy_net_ns+0x155/0x280 net/core/net_namespace.c:387
 [<ffffffff8119f47f>] create_new_namespaces+0x37f/0x730 kernel/nsproxy.c:106
 [<ffffffff8119fac1>] copy_namespaces+0x291/0x320 kernel/nsproxy.c:164
 [<ffffffff8112d449>] copy_process.part.39+0x1e39/0x5f70 kernel/fork.c:1658
 [<ffffffff81131a78>] copy_process kernel/fork.c:1482 [inline]
 [<ffffffff81131a78>] _do_fork+0x1b8/0xd50 kernel/fork.c:1940
 [<ffffffff811326e7>] SYSC_clone kernel/fork.c:2050 [inline]
 [<ffffffff811326e7>] SyS_clone+0x37/0x50 kernel/fork.c:2044
 [<ffffffff81006437>] do_syscall_64+0x197/0x490 arch/x86/entry/common.c:280
 [<ffffffff8396598d>] entry_SYSCALL64_slow_path+0x25/0x25

Showing all locks held in the system:
3 locks held by kworker/u4:2/171:
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118a321>] __write_once_size include/linux/compiler.h:272 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118a321>] atomic64_set arch/x86/include/asm/atomic64_64.h:33 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118a321>] atomic_long_set include/asm-generic/atomic-long.h:56 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118a321>] set_work_data kernel/workqueue.c:615 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118a321>] set_work_pool_and_clear_pending kernel/workqueue.c:642 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118a321>] process_one_work+0x691/0x15c0 kernel/workqueue.c:2089
 #1:  (net_cleanup_work){+.+.+.}, at: [<ffffffff8118a353>] process_one_work+0x6c3/0x15c0 kernel/workqueue.c:2093
 #2:  (net_mutex){+.+.+.}, at: [<ffffffff82f40dd7>] cleanup_net+0x137/0x600 net/core/net_namespace.c:420
2 locks held by khungtaskd/548:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136ae05>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136ae05>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.?.+..}, at: [<ffffffff812341f4>] debug_show_all_locks+0x74/0x290 kernel/locking/lockdep.c:4329
2 locks held by getty/3328:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff83963aa2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff8213c2cc>] n_tty_read+0x1ec/0x1680 drivers/tty/n_tty.c:2133
2 locks held by getty/3329:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff83963aa2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff8213c2cc>] n_tty_read+0x1ec/0x1680 drivers/tty/n_tty.c:2133
2 locks held by getty/3330:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff83963aa2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff8213c2cc>] n_tty_read+0x1ec/0x1680 drivers/tty/n_tty.c:2133
2 locks held by getty/3331:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff83963aa2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff8213c2cc>] n_tty_read+0x1ec/0x1680 drivers/tty/n_tty.c:2133
2 locks held by getty/3332:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff83963aa2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff8213c2cc>] n_tty_read+0x1ec/0x1680 drivers/tty/n_tty.c:2133
2 locks held by getty/3333:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff83963aa2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff8213c2cc>] n_tty_read+0x1ec/0x1680 drivers/tty/n_tty.c:2133
2 locks held by getty/28498:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff83963aa2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff8213c2cc>] n_tty_read+0x1ec/0x1680 drivers/tty/n_tty.c:2133
1 lock held by syz-executor7/13256:
 #0:  (net_mutex){+.+.+.}, at: [<ffffffff82f413f5>] copy_net_ns+0x155/0x280 net/core/net_namespace.c:387

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

NMI backtrace for cpu 0
CPU: 0 PID: 548 Comm: khungtaskd Not tainted 4.9.39-gf44842e #5
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8ad7d00 ffffffff81eacd59 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810bf310 ffff8801d8ad7d38
 ffffffff81eb7cad 0000000000000000 0000000000000000 ffff8801cd6aca18
Call Trace:
 [<ffffffff81eacd59>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eacd59>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81eb7cad>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81eb7de7>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810bf404>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff8136b3d0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff8136b3d0>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8136b3d0>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8136b3d0>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff8119be55>] kthread+0x265/0x300 kernel/kthread.c:211
 [<ffffffff83965b5a>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.9.39-gf44842e #5
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9e9af00 task.stack: ffff8801d9eb0000
RIP: 0010:[<ffffffff81237575>] 
c [<ffffffff81237575>] trace_hardirqs_on_caller+0x125/0x590 kernel/locking/lockdep.c:2719
RSP: 0018:ffff8801db307848  EFLAGS: 00000046
RAX: 0000000000000046 RBX: ffffffff859278e0 RCX: 000000000000024d
RDX: 0000000000000004 RSI: 0000000000000001 RDI: ffff8801d9e9b708
RBP: ffff8801db307858 R08: ffff8801dac23a48 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff8396510a
R13: 0000000000021480 R14: 0000000000000001 R15: ffffffff841e23e8
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c443b61af0 CR3: 00000001c9569000 CR4: 00000000001406e0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000020000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 0000000000000282
c ffff8801dac23a48
c ffff8801db307868
c ffffffff812379ed
c
 ffff8801db307888
c ffffffff8396510a
c 0000000000021480
c ffff8801d9ebe060
c
 ffff8801db3078e8
c ffffffff812058e5
c fffffbfff094b500
c ffff8801db3078e0
c
Call Trace:
 <IRQ> 
d [<ffffffff812379ed>] trace_hardirqs_on+0xd/0x10 kernel/locking/lockdep.c:2743
 [<ffffffff8396510a>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:162 [inline]
 [<ffffffff8396510a>] _raw_spin_unlock_irqrestore+0x5a/0x70 kernel/locking/spinlock.c:191
 [<ffffffff812058e5>] update_cpu_capacity kernel/sched/fair.c:7746 [inline]
 [<ffffffff812058e5>] update_group_capacity+0x5d5/0xac0 kernel/sched/fair.c:7772
 [<ffffffff812060c0>] update_sd_lb_stats+0x2f0/0x22a0 kernel/sched/fair.c:8117
 [<ffffffff812080fa>] find_busiest_group+0x8a/0xed0 kernel/sched/fair.c:8395
 [<ffffffff81209270>] load_balance+0x330/0x2d30 kernel/sched/fair.c:8669
 [<ffffffff8120daae>] rebalance_domains+0x5de/0xae0 kernel/sched/fair.c:9319
 [<ffffffff8120e2ae>] run_rebalance_domains+0x2fe/0x5e0 kernel/sched/fair.c:9533
 [<ffffffff8396875d>] __do_softirq+0x22d/0x964 kernel/softirq.c:284
 [<ffffffff81149495>] invoke_softirq kernel/softirq.c:364 [inline]
 [<ffffffff81149495>] irq_exit+0x165/0x190 kernel/softirq.c:405
 [<ffffffff810b058b>] smp_reschedule_interrupt+0x6b/0x80 arch/x86/kernel/smp.c:267
 [<ffffffff8396795c>] reschedule_interrupt+0x8c/0xa0 arch/x86/entry/entry_64.S:732
 <EOI> 
d [<ffffffff83964516>] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
 [<ffffffff83963b45>] arch_safe_halt arch/x86/include/asm/paravirt.h:103 [inline]
 [<ffffffff83963b45>] default_idle+0x55/0x360 arch/x86/kernel/process.c:295
 [<ffffffff8106e28a>] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:286
 [<ffffffff83964966>] default_idle_call+0x36/0x60 kernel/sched/idle.c:97
 [<ffffffff8122837e>] cpuidle_idle_call kernel/sched/idle.c:155 [inline]
 [<ffffffff8122837e>] cpu_idle_loop kernel/sched/idle.c:248 [inline]
 [<ffffffff8122837e>] cpu_startup_entry+0x23e/0x2f0 kernel/sched/idle.c:303
 [<ffffffff810b36bc>] start_secondary+0x24c/0x2d0 arch/x86/kernel/smpboot.c:262
Code: 
cd0 
c7c 
c08 
c84 
cd2 
c0f 
c85 
c0c 
c03 
c00 
c00 
c44 
c8b 
c0d 
c84 
c03 
c6f 
c04 
c45 
c85 
cc9 
c0f 
c85 
cc8 
c00 
c00 
c00 
c9c 
c58 
c0f 
c1f 
c44 
c00 
c00 
cf6 
cc4 
c02 
c0f 
c85 
c5a 
c03 
c00 
c00 
c<48> 
cb8 
c00 
c00 
c00 
c00 
c00 
cfc 
cff 
cdf 
c48 
c89 
cda 
c83 
ce3 
c07 
c48 
cc1 
cea 
c03 
c83 
c