INFO: task syz-executor007:3907 blocked for more than 120 seconds.
      Not tainted 4.4.138-g07c0138 #62
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor007 D ffff8801c670fbb8 28144  3907   3904 0x00000000
 ffff8801c670fbb8 0000000000000000 ffff8801d87d68e0 ffffed003b0fad1b
 ffff8801d87d6000 ffff8801db21fdb8 ffff8801db21fde0 ffff8801db21f4d8
 ffff8801db21f4c0 ffff8801d7d29800 ffff8801d87d6000 0000000000000000
Call Trace:
 [<ffffffff838b46ea>] schedule+0x7a/0x1b0 kernel/sched/core.c:3359
 [<ffffffff838b4e83>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3392
 [<ffffffff838bafc7>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff838bafc7>] mutex_lock_nested+0x307/0x850 kernel/locking/mutex.c:621
 [<ffffffff8158477e>] lock_mount+0x8e/0x2c0 fs/namespace.c:2054
 [<ffffffff8158856d>] do_loopback fs/namespace.c:2187 [inline]
 [<ffffffff8158856d>] do_mount+0x96d/0x2860 fs/namespace.c:2827
 [<ffffffff8158ae70>] SYSC_mount fs/namespace.c:3027 [inline]
 [<ffffffff8158ae70>] SyS_mount+0x130/0x1d0 fs/namespace.c:3005
 [<ffffffff838c2725>] entry_SYSCALL_64_fastpath+0x22/0x9e
1 lock held by syz-executor007/3907:
 #0:  (&sb->s_type->i_mutex_key#13){+.+.+.}, at: [<ffffffff8158477e>] lock_mount+0x8e/0x2c0 fs/namespace.c:2054
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 3919 Comm: syz-executor007 Not tainted 4.4.138-g07c0138 #62
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800ace21800 task.stack: ffff8801d7150000
RIP: 0010:[<ffffffff815b29d2>]  [<ffffffff815b29d2>] do_make_slave fs/pnode.c:83 [inline]
RIP: 0010:[<ffffffff815b29d2>]  [<ffffffff815b29d2>] change_mnt_propagation+0xe2/0xb70 fs/pnode.c:130
RSP: 0018:ffff8801d7157b08  EFLAGS: 00000246
RAX: 1ffff10016bfc416 RBX: ffff8801d80e8400 RCX: ffff8801d80e8468
RDX: 0000000000000000 RSI: ffffffff815b29b0 RDI: ffff8800b5fe20b0
RBP: ffff8801d7157b60 R08: ffff8801d80e8468 R09: 0000000000000001
R10: 0000000000000000 R11: ffff8800ace21800 R12: ffff8800b5fe2000
R13: 0000000000040000 R14: dffffc0000000000 R15: ffff8800b5fe22b0
FS:  00007f1dc2ab7700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f024a5a2000 CR3: 00000001d011e000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8157e63d ffff8801d80e8400 0000000000000000 ffff8801d80e8420
 ffff8801d80e84e0 ffffed003b01d084 ffff8801d80e8490 dffffc0000000000
 ffff8801d80e8400 ffff8801c7b45e40 ffff8801d7157c00 ffff8801d7157c28
Call Trace:
 [<ffffffff8157ed56>] umount_tree+0x326/0x810 fs/namespace.c:1501
 [<ffffffff8158714c>] attach_recursive_mnt+0x74c/0x8e0 fs/namespace.c:2035
 [<ffffffff8158744f>] graft_tree+0x16f/0x1f0 fs/namespace.c:2099
 [<ffffffff81589ce8>] do_loopback fs/namespace.c:2220 [inline]
 [<ffffffff81589ce8>] do_mount+0x20e8/0x2860 fs/namespace.c:2827
 [<ffffffff8158ae70>] SYSC_mount fs/namespace.c:3027 [inline]
 [<ffffffff8158ae70>] SyS_mount+0x130/0x1d0 fs/namespace.c:3005
 [<ffffffff838c2725>] entry_SYSCALL_64_fastpath+0x22/0x9e
Code: 13 02 00 00 e8 00 eb d9 ff 49 8d bc 24 b0 00 00 00 48 89 f8 48 c1 e8 03 42 80 3c 30 00 0f 85 41 08 00 00 4d 8b bc 24 b0 00 00 00 <49> 8d 97 50 ff ff ff 48 39 d3 49 89 d4 75 90 48 89 55 d0 e8 c6 
NMI backtrace for cpu 1
CPU: 1 PID: 491 Comm: khungtaskd Not tainted 4.4.138-g07c0138 #62
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bac59800 task.stack: ffff8800bb3a0000
RIP: 0010:[<ffffffff810bfb26>]  [<ffffffff810bfb26>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810bfb26>]  [<ffffffff810bfb26>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810bfb26>]  [<ffffffff810bfb26>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810bfb26>]  [<ffffffff810bfb26>] flat_send_IPI_mask+0xf6/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800bb3a7cc8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8800bb3a7cf0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: 0000000000000002 R15: ffffffff8446f6a0
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000903b10 CR3: 00000001d02ed000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8446f6a0 ffffffff84a18ee0 0000000000000007 fffffbfff0942c8c
 0000000000000040 ffff8800bb3a7d10 ffffffff810b5ae1 ffffffff83c0b460
 0000000000000003 ffff8800bb3a7d68 ffffffff81e19d83 ffffffff8140dd6f
Call Trace:
 [<ffffffff810b5ae1>] nmi_raise_cpu_backtrace+0x61/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81e19d83>] nmi_trigger_all_cpu_backtrace.cold.4+0x70/0xad lib/nmi_backtrace.c:85
 [<ffffffff810b5b84>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff8141a459>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff8141a459>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8141a459>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8141a459>] watchdog.cold.1+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff81190958>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff838c2b55>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510
Code: b3 5f ff f6 c4 10 75 e2 44 89 e8 c1 e0 18 89 04 25 10 b3 5f ff 44 89 f2 09 da 80 cf 04 41 83 fe 02 0f 44 d3 89 14 25 00 b3 5f ff <41> f7 c4 00 02 00 00 75 1a 4c 89 e7 57 9d 0f 1f 44 00 00 e8 02