INFO: task syz-executor0:3890 blocked for more than 140 seconds.
      Not tainted 4.4.140-g789274d #3
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D ffff8801c028f9c8 25360  3890      1 0x20020004
 ffff8801c028f9c8 0000000000000000 ffff8801c771d0e0 ffffed0038ee3a1b
 ffff8801c771c800 ffff8801db31fdb8 ffff8801db31fde0 ffff8801db31f4d8
 ffff8801db31f4c0 ffff8800ba831800 ffff8801c771c800 0000000000000000
Call Trace:
 [<ffffffff838b476a>] schedule+0x7a/0x1b0 kernel/sched/core.c:3359
 [<ffffffff838b4f03>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3392
 [<ffffffff838bb047>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff838bb047>] mutex_lock_nested+0x307/0x850 kernel/locking/mutex.c:621
 [<ffffffff8251b0ab>] lo_ioctl+0x8b/0x1ad0 drivers/block/loop.c:1355
 [<ffffffff8251cba2>] lo_compat_ioctl+0xb2/0x140 drivers/block/loop.c:1551
 [<ffffffff81dffb95>] compat_blkdev_ioctl+0x395/0x3a10 block/compat_ioctl.c:751
 [<ffffffff81628a44>] C_SYSC_ioctl fs/compat_ioctl.c:1592 [inline]
 [<ffffffff81628a44>] compat_SyS_ioctl+0x484/0x2270 fs/compat_ioctl.c:1544
 [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
 [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:459
 [<ffffffff838c40ea>] sysenter_flags_fixed+0xd/0x17
1 lock held by syz-executor0/3890:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff8251b0ab>] lo_ioctl+0x8b/0x1ad0 drivers/block/loop.c:1355
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 491 Comm: khungtaskd Not tainted 4.4.140-g789274d #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bacc3000 task.stack: ffff8800bacb0000
RIP: 0010:[<ffffffff810bff96>]  [<ffffffff810bff96>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810bff96>]  [<ffffffff810bff96>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810bff96>]  [<ffffffff810bff96>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810bff96>]  [<ffffffff810bff96>] flat_send_IPI_mask+0xf6/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800bacb7cc8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8800bacb7cf0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: 0000000000000002 R15: ffffffff8446f6e0
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1840fbb140 CR3: 00000000af596000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8446f6e0 ffffffff84a19060 0000000000000007 fffffbfff0942cbc
 0000000000000040 ffff8800bacb7d10 ffffffff810b5f51 ffffffff83c0b760
 0000000000000003 ffff8800bacb7d68 ffffffff81e19103 ffffffff8140ddaf
Call Trace:
 [<ffffffff810b5f51>] nmi_raise_cpu_backtrace+0x61/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81e19103>] nmi_trigger_all_cpu_backtrace.cold.4+0x70/0xad lib/nmi_backtrace.c:85
 [<ffffffff810b5ff4>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff8141a499>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff8141a499>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8141a499>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8141a499>] watchdog.cold.1+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff81190998>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff838c2bd5>] 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 d2 
NMI backtrace for cpu 1
CPU: 1 PID: 14958 Comm: syz-executor4 Not tainted 4.4.140-g789274d #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801bb154800 task.stack: ffff8801d95c0000
RIP: 0010:[<ffffffff8100aeb6>]  [<ffffffff8100aeb6>] copy_kernel_to_xregs arch/x86/include/asm/fpu/internal.h:354 [inline]
RIP: 0010:[<ffffffff8100aeb6>]  [<ffffffff8100aeb6>] __copy_kernel_to_fpregs arch/x86/include/asm/fpu/internal.h:454 [inline]
RIP: 0010:[<ffffffff8100aeb6>]  [<ffffffff8100aeb6>] copy_kernel_to_fpregs arch/x86/include/asm/fpu/internal.h:478 [inline]
RIP: 0010:[<ffffffff8100aeb6>]  [<ffffffff8100aeb6>] switch_fpu_finish arch/x86/include/asm/fpu/internal.h:648 [inline]
RIP: 0010:[<ffffffff8100aeb6>]  [<ffffffff8100aeb6>] __switch_to+0x936/0xe30 arch/x86/kernel/process_64.c:398
RSP: 0018:ffff8801cf92fa18  EFLAGS: 00000002
RAX: 00000000ffffffff RBX: ffff8801c89e6000 RCX: 1ffff1003762ab5f
RDX: 00000000ffffffff RSI: 00000000a6744700 RDI: ffff8801c89e73c0
RBP: ffff8801cf92fac8 R08: ffff8801bb155bc0 R09: 0000000000000001
R10: 0000000000000000 R11: ffff8801bb154a70 R12: ffff8801bb154800
R13: ffff8801c89e73c0 R14: 0000000000000063 R15: 0000000000000063
FS:  00007f49a6744700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1840fbb140 CR3: 00000001d39fd000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000046 ffff8801db31f4c0 1ffff10039f25f48 ffff8801db308840
 ffff880100000001 0000000041b58ab3 ffffffff841d9aa2 ffffffff8100a580
 ffffed003913cd1b ffff8801c89e73c0 ffff8801c89e68d8 00000001c89e6000
Call Trace:
 <UNK> 
dCode: 52 12 00 c6 05 a2 7c 9f 03 01 e9 f2 fc ff ff bf 9a 00 00 00 e8 7c e1 02 00 84 c0 74 b9 b8 ff ff ff ff 4c 89 ef 89 c2 48 0f ae 2f <31> c0 85 c0 0f 84 cc fc ff ff 80 3d 6e 7c 9f 03 00 0f 85 bf fc