INFO: task syz-executor3:3757 blocked for more than 140 seconds.
      Not tainted 4.4.140-ged9bdc8 #68
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor3   D ffff8801c3617a68 27568  3757      1 0x00000004
 ffff8801c3617a68 0000000000000000 ffff8800b21d88e0 ffffed001643b11b
 ffff8800b21d8000 ffff8801db21fdb8 ffff8801db21fde0 ffff8801db21f4d8
 ffff8801db21f4c0 ffff8801ce113000 ffff8800b21d8000 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
 [<ffffffff81db72e8>] __blkdev_driver_ioctl block/ioctl.c:288 [inline]
 [<ffffffff81db72e8>] blkdev_ioctl+0x7b8/0x19c0 block/ioctl.c:584
 [<ffffffff815d400e>] block_ioctl+0xde/0x120 fs/block_dev.c:1625
 [<ffffffff81559ccf>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff81559ccf>] file_ioctl fs/ioctl.c:470 [inline]
 [<ffffffff81559ccf>] do_vfs_ioctl+0x63f/0xf40 fs/ioctl.c:605
 [<ffffffff8155a65f>] SYSC_ioctl fs/ioctl.c:622 [inline]
 [<ffffffff8155a65f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613
 [<ffffffff838c27a5>] entry_SYSCALL_64_fastpath+0x22/0x9e
1 lock held by syz-executor3/3757:
 #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: 22711 Comm: syz-executor7 Not tainted 4.4.140-ged9bdc8 #68
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d4834800 task.stack: ffff8800b6c90000
RIP: 0010:[<ffffffff81351516>]  [<ffffffff81351516>] __read_once_size include/linux/compiler.h:218 [inline]
RIP: 0010:[<ffffffff81351516>]  [<ffffffff81351516>] check_kcov_mode kernel/kcov.c:68 [inline]
RIP: 0010:[<ffffffff81351516>]  [<ffffffff81351516>] __sanitizer_cov_trace_pc+0x26/0x50 kernel/kcov.c:100
RSP: 0018:ffff8800b6c97b88  EFLAGS: 00000246
RAX: ffff8801d4834800 RBX: ffff8801cd8029e0 RCX: dffffc0000000000
RDX: 0000000000000002 RSI: ffffffff8251c60c RDI: ffff8801cd802a2c
RBP: ffff8800b6c97b88 R08: ffff8801d4835128 R09: 0000000000000001
R10: 0000000000000000 R11: ffff8801d4834800 R12: ffff8801cd8029e0
R13: ffff8800b9c65c00 R14: ffff8801d6957600 R15: ffff8801d6957758
FS:  00007f40a64c5700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff2c99df28 CR3: 00000000b3586000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8800b6c97c18 ffffffff8251c60c 0000000b0000004c 0000000100000000
 ffff8800b6c97d20 ffff8801d6957750 0000000000006000 0000000041b58ab3
 ffff8801cd802bc8 ffff8800bad9e600 ffff8800b9c65cf0 000000000002001d
Call Trace:
 [<ffffffff8251c60c>] loop_set_fd drivers/block/loop.c:900 [inline]
 [<ffffffff8251c60c>] lo_ioctl+0x15ec/0x1ad0 drivers/block/loop.c:1358
 [<ffffffff81db72e8>] __blkdev_driver_ioctl block/ioctl.c:288 [inline]
 [<ffffffff81db72e8>] blkdev_ioctl+0x7b8/0x19c0 block/ioctl.c:584
 [<ffffffff815d400e>] block_ioctl+0xde/0x120 fs/block_dev.c:1625
 [<ffffffff81559ccf>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff81559ccf>] file_ioctl fs/ioctl.c:470 [inline]
 [<ffffffff81559ccf>] do_vfs_ioctl+0x63f/0xf40 fs/ioctl.c:605
 [<ffffffff8155a65f>] SYSC_ioctl fs/ioctl.c:622 [inline]
 [<ffffffff8155a65f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613
 [<ffffffff838c27a5>] entry_SYSCALL_64_fastpath+0x22/0x9e
Code: ff 0f 1f 40 00 55 48 89 e5 65 48 8b 04 25 00 67 01 00 65 8b 15 8c 51 cc 7e 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 
NMI backtrace for cpu 1
CPU: 1 PID: 492 Comm: khungtaskd Not tainted 4.4.140-ged9bdc8 #68
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d8c48000 task.stack: ffff8801d8e78000
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:ffff8801d8e7fcc8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8801d8e7fcf0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: 0000000000000002 R15: ffffffff8446f6e0
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001775000 CR3: 00000000b40b8000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8446f6e0 ffffffff84a19060 0000000000000007 fffffbfff0942cbc
 0000000000000040 ffff8801d8e7fd10 ffffffff810b5f51 ffffffff83c0b760
 0000000000000003 ffff8801d8e7fd68 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