INFO: task syz-executor.3:31875 blocked for more than 140 seconds.
      Not tainted 4.4.174+ #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.3  D ffff88009d0379d8 29184 31875   2155 0x00000004
 ffff88009d0379d8 ffff88009d028000 c46ae5f159eeb53a ffff88009d028000
 0000000000000000 ffff88009d028800 ffff8801db71f180 ffff8801db71f1a8
 ffff8801db71e898 ffff8800b5050000 ffff88009d028000 ffffed0013a06001
Call Trace:
 [<ffffffff82709b79>] schedule+0x99/0x1d0 kernel/sched/core.c:3355
 [<ffffffff8270a333>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3388
 [<ffffffff8270c492>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8270c492>] mutex_lock_nested+0x3c2/0xb80 kernel/locking/mutex.c:621
 [<ffffffff8221b16a>] copy_net_ns+0xca/0x250 net/core/net_namespace.c:387
 [<ffffffff81136a90>] create_new_namespaces+0x2f0/0x670 kernel/nsproxy.c:95
 [<ffffffff8113709a>] copy_namespaces+0x28a/0x320 kernel/nsproxy.c:150
 [<ffffffff810cd012>] copy_process+0x2472/0x68a0 kernel/fork.c:1522
 [<ffffffff810d186e>] _do_fork+0x14e/0xdc0 kernel/fork.c:1806
 [<ffffffff810d25b7>] SYSC_clone kernel/fork.c:1917 [inline]
 [<ffffffff810d25b7>] SyS_clone+0x37/0x50 kernel/fork.c:1911
 [<ffffffff82718cb7>] tracesys+0x88/0x8d
1 lock held by syz-executor.3/31875:
 #0:  (net_mutex){+.+.+.}, at: [<ffffffff8221b16a>] copy_net_ns+0xca/0x250 net/core/net_namespace.c:387
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 20 Comm: khungtaskd Not tainted 4.4.174+ #4
task: ffff8801da6f4740 task.stack: ffff8800001d0000
RIP: 0010:[<ffffffff8109b617>]  [<ffffffff8109b617>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:62 [inline]
RIP: 0010:[<ffffffff8109b617>]  [<ffffffff8109b617>] flat_send_IPI_mask+0xf7/0x1b0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800001d7c88  EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fc300
RBP: ffff8800001d7cb8 R08: 0000000000000018 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000003000000 R14: ffffffff82e5f2e0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000fffffff8 CR3: 000000018f0ad000 CR4: 00000000001606b0
Stack:
 0000000000000001 ffffffff82e5f2e0 ffffffff831a6ac0 fffffbfff0634c34
 000000000001b6c0 0000000000000008 ffff8800001d7cd8 ffffffff81092bee
 0000000000000008 ffffffff82924260 ffff8800001d7d30 ffffffff81ab8252
Call Trace:
 [<ffffffff81092bee>] nmi_raise_cpu_backtrace+0x5e/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81ab8252>] nmi_trigger_all_cpu_backtrace.cold+0xa1/0xae lib/nmi_backtrace.c:85
 [<ffffffff81092ca4>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff813b4762>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff813b4762>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813b4762>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813b4762>] watchdog.cold+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff811342c3>] kthread+0x273/0x310 kernel/kthread.c:211
 [<ffffffff82718fc5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537
Code: 00 c3 5f ff 80 e6 10 75 e1 41 c1 e5 18 44 89 2c 25 10 c3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 c3 5f ff <41> f7 c4 00 02 00 00 75 1e 4c 89 e7 57 9d 0f 1f 44 00 00 e8 f1 
NMI backtrace for cpu 1
CPU: 1 PID: 14478 Comm: syz-executor.3 Not tainted 4.4.174+ #4
task: ffff880179c6df00 task.stack: ffff880179e40000
RIP: 0010:[<ffffffff810a20b6>]  [<ffffffff810a20b6>] native_set_pte_at+0x46/0xe0 arch/x86/include/asm/pgtable.h:779
RSP: 0018:ffff880179e47a28  EFLAGS: 00000296
RAX: dffffc0000000000 RBX: 1ffff1002f3c8f46 RCX: 80000001c3fdb007
RDX: ffff880069e970b0 RSI: ffffed002f3c8f46 RDI: ffff880179f6d500
RBP: ffff880179e47aa0 R08: 0000000000000003 R09: ffff880179c6e860
R10: ffffffff83a47360 R11: 0000000000000000 R12: 80000001c3fdb007
R13: ffff8800693280b0 R14: 00007fb7c5a16000 R15: dffffc0000000000
FS:  00007fb7c49e5700(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000017a1c5000 CR4: 00000000001606b0
Stack:
 ffffffff81432030 0000000041b58ab3 ffffffff82c48c3c ffffffff810a2070
 0000000000000246 80000001c3fda007 ffff88018c957f20 0000000000000001
 0000000000000000 5c42413d00baecd2 0000000000000008 80000001c3fdb007
Call Trace:
 [<ffffffff81437fe8>] set_pte_at arch/x86/include/asm/paravirt.h:500 [inline]
 [<ffffffff81437fe8>] copy_one_pte mm/memory.c:915 [inline]
 [<ffffffff81437fe8>] copy_pte_range mm/memory.c:958 [inline]
 [<ffffffff81437fe8>] copy_pmd_range mm/memory.c:1008 [inline]
 [<ffffffff81437fe8>] copy_pud_range mm/memory.c:1030 [inline]
 [<ffffffff81437fe8>] copy_page_range+0xb58/0x1530 mm/memory.c:1092
 [<ffffffff810cef1f>] dup_mmap kernel/fork.c:517 [inline]
 [<ffffffff810cef1f>] dup_mm kernel/fork.c:985 [inline]
 [<ffffffff810cef1f>] copy_mm kernel/fork.c:1039 [inline]
 [<ffffffff810cef1f>] copy_process+0x437f/0x68a0 kernel/fork.c:1519
 [<ffffffff810d186e>] _do_fork+0x14e/0xdc0 kernel/fork.c:1806
 [<ffffffff810d253f>] sys_fork+0x1f/0x30 kernel/fork.c:1877
 [<ffffffff82718cb7>] tracesys+0x88/0x8d
Code: ec 68 48 c7 45 90 b3 8a b5 41 48 8d 34 03 48 c7 45 98 3c 8c c4 82 48 c7 45 a0 70 20 0a 81 c7 06 f1 f1 f1 f1 c7 46 04 00 f3 f3 f3 <65> 48 8b 3c 25 28 00 00 00 48 89 7d e8 31 ff 48 8d 7d b0 48 89