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-executor0:9564 blocked for more than 120 seconds.
      Not tainted 4.4.125-g38f41ec #63
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D ffff8801c7c87c38 29016  9564      1 0x00000004
 ffff8801c7c87c38 ffff8801d3090000 0000000000000000 0000000000000007
 ffff8801d3090000 ffff8801db21fdb8 ffff8801db21fde0 ffff8801db21f4d8
 ffff8801db21f4c0 ffffffff84217840 ffff8801d3090000 0000000000000000
Call Trace:
 [<ffffffff8376b82a>] schedule+0x7a/0x1b0 kernel/sched/core.c:3359
 [<ffffffff8376c023>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3392
 [<ffffffff837705e6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff837705e6>] mutex_lock_nested+0x306/0x850 kernel/locking/mutex.c:621
 [<ffffffff82e33be7>] copy_net_ns+0xc7/0x190 net/core/net_namespace.c:368
 [<ffffffff81193166>] create_new_namespaces+0x2f6/0x610 kernel/nsproxy.c:95
 [<ffffffff81193a1e>] unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:190
 [<ffffffff8112cc8a>] SYSC_unshare kernel/fork.c:2068 [inline]
 [<ffffffff8112cc8a>] SyS_unshare+0x3da/0x700 kernel/fork.c:2018
 [<ffffffff83779965>] entry_SYSCALL_64_fastpath+0x22/0x9e
1 lock held by syz-executor0/9564:
 #0:  (net_mutex){+.+.+.}, at: [<ffffffff82e33be7>] copy_net_ns+0xc7/0x190 net/core/net_namespace.c:368
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.125-g38f41ec #63
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff84217840 task.stack: ffffffff84200000
RIP: 0010:[<ffffffff810c353c>]  [<ffffffff810c353c>] native_apic_mem_write+0xc/0x10 arch/x86/include/asm/apic.h:94
RSP: 0018:ffffffff84207c30  EFLAGS: 00000046
RAX: dffffc0000000000 RBX: ffffffff8426f5a0 RCX: 0000000000000020
RDX: 1ffffffff084ded1 RSI: 0000000001770017 RDI: 0000000000000380
RBP: ffffffff84207c30 R08: ffff88021fffd018 R09: 0000000000000006
R10: ffffed0043fffa01 R11: 0000000000000000 R12: 0000000001770017
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000003
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0727be09b8 CR3: 00000001ca44e000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff84207c50 ffffffff810b086a 0000000000000000 ffff8801db217fc0
 ffffffff84207c90 ffffffff812d06fa 000000383621a7fe ffff8801db217fc0
 0000000000000001 ffff8801db219640 0000000000000001 0000000000000000
Call Trace:
 [<ffffffff810b086a>] apic_write arch/x86/include/asm/apic.h:392 [inline]
 [<ffffffff810b086a>] lapic_next_event+0x5a/0x90 arch/x86/kernel/apic/apic.c:458
 [<ffffffff812d06fa>] clockevents_program_event+0x28a/0x350 kernel/time/clockevents.c:339
 [<ffffffff812d5588>] tick_program_event+0xa8/0x110 kernel/time/tick-oneshot.c:47
 [<ffffffff812acc66>] hrtimer_force_reprogram kernel/time/hrtimer.c:601 [inline]
 [<ffffffff812acc66>] __remove_hrtimer+0x1f6/0x250 kernel/time/hrtimer.c:929
 [<ffffffff812ad6d3>] remove_hrtimer kernel/time/hrtimer.c:958 [inline]
 [<ffffffff812ad6d3>] hrtimer_try_to_cancel+0x2b3/0x660 kernel/time/hrtimer.c:1059
 [<ffffffff812adaa2>] hrtimer_cancel+0x22/0x40 kernel/time/hrtimer.c:1079
 [<ffffffff812d613e>] tick_nohz_restart+0x1e/0x190 kernel/time/tick-sched.c:559
 [<ffffffff812d8197>] tick_nohz_restart_sched_tick kernel/time/tick-sched.c:726 [inline]
 [<ffffffff812d8197>] tick_nohz_idle_exit+0x247/0x3d0 kernel/time/tick-sched.c:946
 [<ffffffff81221cf5>] cpu_idle_loop kernel/sched/idle.c:267 [inline]
 [<ffffffff81221cf5>] cpu_startup_entry+0x2a5/0x8f0 kernel/sched/idle.c:301
 [<ffffffff837667b9>] rest_init+0x189/0x190 init/main.c:410
 [<ffffffff84823811>] start_kernel+0x6b9/0x6ee init/main.c:682
 [<ffffffff84822312>] x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
 [<ffffffff84822454>] x86_64_start_kernel+0x140/0x163 arch/x86/kernel/head64.c:185
Code: a2 06 00 66 90 66 2e 0f 1f 84 00 00 00 00 00 55 be 01 00 00 00 48 89 e5 e8 42 d6 1b 00 5d c3 55 89 ff 48 89 e5 89 b7 00 b0 5f ff <5d> c3 66 90 48 b8 00 00 00 00 00 fc ff df 55 48 89 e5 53 89 fb 
NMI backtrace for cpu 1
CPU: 1 PID: 486 Comm: khungtaskd Not tainted 4.4.125-g38f41ec #63
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bad88000 task.stack: ffff8800bad68000
RIP: 0010:[<ffffffff810c3f87>]  [<ffffffff810c3f87>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810c3f87>]  [<ffffffff810c3f87>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810c3f87>]  [<ffffffff810c3f87>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810c3f87>]  [<ffffffff810c3f87>] flat_send_IPI_mask+0xf7/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800bad6fcb8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8800bad6fce0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: ffffffff8426f5a0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0695e6b000 CR3: 00000001ca44e000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8426f5a0 ffffffff847f0b40 fffffbfff08fdc1c dffffc0000000000
 ffff8801db31bca0 ffff8800bad6fd00 ffffffff810b9abb ffffffff839f6dc0
 0000000000000003 ffff8800bad6fd60 ffffffff81d11764 ffffffff8141b993
Call Trace:
 [<ffffffff810b9abb>] nmi_raise_cpu_backtrace+0x5b/0x70 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81d11764>] nmi_trigger_all_cpu_backtrace+0x4a4/0x550 lib/nmi_backtrace.c:85
 [<ffffffff810b9b54>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff813695ca>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff813695ca>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813695ca>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813695ca>] watchdog+0x6fa/0xae0 kernel/hung_task.c:238
 [<ffffffff81190b48>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff83779d95>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510
unregister_netdevice: waiting for lo to become free. Usage count = 4
Code: b3 5f ff f6 c4 10 75 e1 44 89 e8 c1 e0 18 89 04 25 10 b3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 b3 5f ff <41> f7 c4 00 02 00 00 74 1a e8 2b 33 17 00 4c 89 e7 57 9d 0f 1f