unregister_netdevice: waiting for lo to become free. Usage count = 2
INFO: task syz-executor3:29927 blocked for more than 120 seconds.
      Not tainted 4.9.39-g72a0c9f #6
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor3   D28992 29927   3341 0x00000004
 ffff8801c5398000 0000000000000000 ffff8801944c8580 ffffffff844268c0
 ffff8801db221498 ffff8801c8c7fa18 ffffffff83954b2b 0000000000000000
 0000000000000007 00ff8801c5398000 ffff8801db221db0 ffff8801db221dd8
Call Trace:
 [<ffffffff839560e2>] schedule+0x92/0x1b0 kernel/sched/core.c:3624
 [<ffffffff83956a53>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3657
 [<ffffffff8395bdaf>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8395bdaf>] 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
 [<ffffffff83965a4d>] entry_SYSCALL64_slow_path+0x25/0x25

Showing all locks held in the system:
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
1 lock held by rsyslogd/3225:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d939f>] __fdget_pos+0x9f/0xc0 fs/file.c:781
2 locks held by getty/3308:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff83963b92>] 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/3309:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff83963b92>] 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/3310:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff83963b92>] 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/3311:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff83963b92>] 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/3312:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff83963b92>] 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/3313:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff83963b92>] 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
3 locks held by kworker/u4:3/3629:
 #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 getty/17015:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff83963b92>] 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-executor3/29927:
 #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-g72a0c9f #6
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8aa7d00 ffffffff81eacd59 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810bf310 ffff8801d8aa7d38
 ffffffff81eb7cad 0000000000000000 0000000000000000 ffff8801c5398398
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
 [<ffffffff83965c1a>] 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-g72a0c9f #6
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9e9af00 task.stack: ffff8801d9eb0000
RIP: 0010:[<ffffffff812066bd>] 
c [<ffffffff812066bd>] update_sg_lb_stats kernel/sched/fair.c:7994 [inline]
RIP: 0010:[<ffffffff812066bd>] 
c [<ffffffff812066bd>] update_sd_lb_stats+0x8ed/0x22a0 kernel/sched/fair.c:8120
RSP: 0018:ffff8801db3078f8  EFLAGS: 00000206
RAX: 0000000000000ff3 RBX: ffff8801db3079d0 RCX: 000000000000024d
RDX: 00000000000001e9 RSI: 0000000000000040 RDI: ffff8801db3079f0
RBP: ffff8801db307a78 R08: 0000000000000040 R09: 0000000000000000
R10: ffff8801db221480 R11: 1ffff1003b6443c2 R12: ffff8801db307cc8
R13: ffff8801db307ae8 R14: ffff8801db3079d8 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c445f95370 CR3: 00000001cbe1c000 CR4: 00000000001406e0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffff8801db307938
c 1ffff1003b660f35
c 1ffff1003b660f36
c ffff8801db307cf4
c
 00000000db307af8
c ffff8801db307b00
c ffff8801db307af8
c ffff8801db307cdc
c
 ffff8801db307ae8
c ffffed003b660f99
c ffff8801d9dbff70
c 0000000000021480
c
Call Trace:
 [<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
 [<ffffffff8396881d>] __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
 [<ffffffff83967a1c>] reschedule_interrupt+0x8c/0xa0 arch/x86/entry/entry_64.S:732
 <EOI> 
d [<ffffffff83964606>] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
 [<ffffffff83963c35>] arch_safe_halt arch/x86/include/asm/paravirt.h:103 [inline]
 [<ffffffff83963c35>] default_idle+0x55/0x360 arch/x86/kernel/process.c:295
 [<ffffffff8106e28a>] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:286
 [<ffffffff83964a56>] 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: 
c38 
c00 
c0f 
c85 
cc8 
c12 
c00 
c00 
c4c 
c89 
cf0 
c48 
c89 
c4b 
c20 
c48 
cc1 
ce8 
c03 
c42 
c80 
c3c 
c38 
c00 
c0f 
c85 
cca 
c12 
c00 
c00 
c48 
c8b 
c43 
c08 
c31 
cd2 
c48 
cc1 
ce0 
c0a 
c48 
cf7 
cf1 
c<49> 
c89 
cc1 
c48 
c89 
cd8 
c48 
cc1 
ce8 
c03 
c42 
c80 
c3c 
c38 
c00 
c0f 
c85 
cc3 
c12 
c00 
c00 
c