INFO: task syz-executor0:3889 blocked for more than 140 seconds.
      Not tainted 4.4.140-ged9bdc8 #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D ffff8800a69ef9c8 27200  3889      1 0x20020004
 ffff8800a69ef9c8 0000000000000000 ffff8801d8f508e0 ffffed003b1ea11b
 ffff8801d8f50000 ffff8801db31fdb8 ffff8801db31fde0 ffff8801db31f4d8
 ffff8801db31f4c0 ffff8800b79f4800 ffff8801d8f50000 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-executor0/3889:
 #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-ged9bdc8 #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d8dd8000 task.stack: ffff8801d8dc8000
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:ffff8801d8dcfcc8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8801d8dcfcf0 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: 00007f19d3088000 CR3: 00000001cea0b000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8446f6e0 ffffffff84a19060 0000000000000007 fffffbfff0942cbc
 0000000000000040 ffff8801d8dcfd10 ffffffff810b5f51 ffffffff83c0b760
 0000000000000003 ffff8801d8dcfd68 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: 11463 Comm: syz-executor7 Not tainted 4.4.140-ged9bdc8 #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d6ebb000 task.stack: ffff8801d91c8000
RIP: 0010:[<ffffffff8135152f>]  [<ffffffff8135152f>] __sanitizer_cov_trace_pc+0x3f/0x50 kernel/kcov.c:105
RSP: 0018:ffff8801d91cfae8  EFLAGS: 00000216
RAX: 0000000000040000 RBX: ffff8801d33f1e60 RCX: ffffc9000208e000
RDX: 0000000000040000 RSI: ffffffff8251c5ca RDI: ffff8801c850fbb0
RBP: ffff8801d91cfae8 R08: ffff8801d6ebb928 R09: 0000000000000001
R10: 0000000000000000 R11: ffff8801d6ebb000 R12: ffff8801d33f1e60
R13: ffff8801d33f05c0 R14: ffff8801d7e00d80 R15: ffff8801d7e00ed8
FS:  0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f57a7b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00007f72ffbc5140 CR3: 00000000b4a31000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801d91cfb78 ffffffff8251c5ca ffff8801d7c95060 0000000000000001
 ffff8801d91cfb88 ffff8801d7e00ed0 0000000000006000 ffff8801d6ebb8d8
 ffff8801d33f2048 ffff8801d92acc00 ffff8801d33f06b0 dffffc000002001d
Call Trace:
 [<ffffffff8251c5ca>] is_loop_device drivers/block/loop.c:715 [inline]
 [<ffffffff8251c5ca>] loop_set_fd drivers/block/loop.c:897 [inline]
 [<ffffffff8251c5ca>] lo_ioctl+0x15aa/0x1ad0 drivers/block/loop.c:1358
 [<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
Code: 81 e2 00 01 1f 00 48 8b 75 08 75 2b 8b 90 98 12 00 00 83 fa 02 75 20 48 8b 88 a0 12 00 00 8b 80 9c 12 00 00 48 8b 11 48 83 c2 01 <48> 39 d0 76 07 48 89 34 d1 48 89 11 5d c3 0f 1f 00 55 48 89 e5