INFO: task syz-executor2:3795 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-executor2   D ffff8801c4f67a68 27376  3795   3791 0x00000000
 ffff8801c4f67a68 0000000000000000 ffff8801cc8120e0 ffffed003990241b
 ffff8801cc811800 ffff8801db31fdb8 ffff8801db31fde0 ffff8801db31f4d8
 ffff8801db31f4c0 ffff8801d9a86000 ffff8801cc811800 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-executor2/3795:
 #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 #68
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d8e3c800 task.stack: ffff8801d8e50000
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:ffff8801d8e57cc8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8801d8e57cf0 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: 00007fccf66a395b CR3: 00000001d20e9000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8446f6e0 ffffffff84a19060 0000000000000007 fffffbfff0942cbc
 0000000000000040 ffff8801d8e57d10 ffffffff810b5f51 ffffffff83c0b760
 0000000000000003 ffff8801d8e57d68 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: 6930 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: ffff8800baae3000 task.stack: ffff8801bbbf8000
RIP: 0010:[<ffffffff8251c578>]  [<ffffffff8251c578>] is_loop_device drivers/block/loop.c:713 [inline]
RIP: 0010:[<ffffffff8251c578>]  [<ffffffff8251c578>] loop_set_fd drivers/block/loop.c:897 [inline]
RIP: 0010:[<ffffffff8251c578>]  [<ffffffff8251c578>] lo_ioctl+0x1558/0x1ad0 drivers/block/loop.c:1358
RSP: 0018:ffff8801bbbffb98  EFLAGS: 00000a02
RAX: 1ffff10017418579 RBX: ffff8800ba0c2bc8 RCX: dffffc0000000000
RDX: 0000000000040000 RSI: ffffffff8251c515 RDI: ffff8801d1e79bb0
RBP: ffff8801bbbffc18 R08: ffff8800baae3928 R09: 0000000000000001
R10: 0000000000000000 R11: ffff8800baae3000 R12: ffff8800ba0c29e0
R13: ffff8801d9c16d40 R14: ffff8801d69a9200 R15: ffff8801d69a9358
FS:  00007f13f3b98700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f12e713c9b8 CR3: 00000000b8e06000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000b0000004c 0000000100000000 0000000000000000 ffff8801d69a9350
 0000000000006000 0000000041b58ab3 ffff8800ba0c2bc8 ffff8801cc153c00
 ffff8801d9c16e30 000000000002001d 0000000000000000 ffff8801d9c16d40
Call Trace:
 [<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: 00 00 48 89 f8 48 c1 e8 03 80 3c 08 00 0f 85 cd 03 00 00 48 8b 9b b0 01 00 00 48 b9 00 00 00 00 00 fc ff df 48 89 d8 48 c1 e8 03 <80> 3c 08 00 0f 85 9e 03 00 00 48 8b 1b 48 85 db 0f 84 8f fd ff