INFO: task syz-executor4:6419 blocked for more than 120 seconds.
      Not tainted 4.9.69-g3f1d77c #108
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor4   D30144  6419   3581 0x00000004
 ffff8801a5abc800 ffff8801a53dc540 ffff8801a8678000 ffff8801a8389800
 ffff8801db321418 ffff8801a836fba8 ffffffff8389932b 0000000000000001
 0000000000000007 00ff8801a5abc800 ffff8801db321ce8 ffff8801db321d10
Call Trace:
 [<ffffffff8389a8cf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3550
 [<ffffffff8389b253>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3583
 [<ffffffff838a0862>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff838a0862>] mutex_lock_nested+0x312/0x870 kernel/locking/mutex.c:621
 [<ffffffff824b1326>] loop_control_ioctl+0x176/0x300 drivers/block/loop.c:1907
 [<ffffffff815aa7da>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815aa7da>] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 [<ffffffff815ab7ff>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815ab7ff>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff838aab05>] entry_SYSCALL_64_fastpath+0x23/0xc6

Showing all locks held in the system:
2 locks held by khungtaskd/514:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fe15>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fe15>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff812355e0>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
2 locks held by getty/3302:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a8cf2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff82002084>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
2 locks held by syz-executor4/6419:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff824b122a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1893
 #1:  (&lo->lo_ctl_mutex#2){+.+...}, at: [<ffffffff824b1326>] loop_control_ioctl+0x176/0x300 drivers/block/loop.c:1907
1 lock held by syz-executor1/6396:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff824aed6f>] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337
1 lock held by syz-executor1/6402:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff824aed6f>] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 514 Comm: khungtaskd Not tainted 4.9.69-g3f1d77c #108
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8eefd00 ffffffff81d90a29 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810ba1a0 ffff8801d8eefd38
 ffffffff81d9bb4d 0000000000000001 0000000000000000 ffff8801d8380418
Call Trace:
 [<ffffffff81d90a29>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d90a29>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9bb4d>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d9bc87>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810ba294>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff813703e0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff813703e0>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813703e0>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813703e0>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff811985ed>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838aadaa>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.69-g3f1d77c #108
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff84426880 task.stack: ffffffff84400000
RIP: 0010:[<ffffffff813681f7>] 
c [<ffffffff813681f7>] __read_once_size include/linux/compiler.h:243 [inline]
RIP: 0010:[<ffffffff813681f7>] 
c [<ffffffff813681f7>] __sanitizer_cov_trace_pc+0x27/0x60 kernel/kcov.c:67
RSP: 0018:ffff8801db207f88  EFLAGS: 00000046
RAX: ffffffff84426880 RBX: 0000000000017e90 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff84407d18
RBP: ffff8801db207f88 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff84a2e7f8 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001c85000 CR3: 00000001d034e000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801db207f98
c ffffffff81df7a29
c ffff8801db207fb8
c ffffffff81293aa5
c
 0000000000000000
c ffffffff84a1f6e8
c ffff8801db207fd0
c ffffffff81144c2a
c
 ffffffff84a1f6e8
c ffff8801db207fe8
c ffffffff838aeeba
c ffffffff84a1f6e8
c
Call Trace:
 <IRQ> 
d [<ffffffff81df7a29>] debug_smp_processor_id+0x9/0x20 lib/smp_processor_id.c:56
 [<ffffffff81293aa5>] rcu_irq_enter+0x15/0x120 kernel/rcu/tree.c:938
 [<ffffffff81144c2a>] irq_enter+0xa/0xd0 kernel/softirq.c:338
 [<ffffffff838aeeba>] smp_reschedule_interrupt+0xa/0x80 arch/x86/kernel/smp.c:264
 [<ffffffff838acb9c>] reschedule_interrupt+0x8c/0xa0 arch/x86/entry/entry_64.S:732
 <EOI> 
d [<ffffffff838a9766>] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
 [<ffffffff838a8d95>] arch_safe_halt arch/x86/include/asm/paravirt.h:103 [inline]
 [<ffffffff838a8d95>] default_idle+0x55/0x360 arch/x86/kernel/process.c:295
 [<ffffffff8106bada>] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:286
 [<ffffffff838a9ba6>] default_idle_call+0x36/0x60 kernel/sched/idle.c:97
 [<ffffffff81223be0>] cpuidle_idle_call kernel/sched/idle.c:155 [inline]
 [<ffffffff81223be0>] cpu_idle_loop kernel/sched/idle.c:248 [inline]
 [<ffffffff81223be0>] cpu_startup_entry+0x2b0/0x380 kernel/sched/idle.c:303
 [<ffffffff83895f74>] rest_init+0x184/0x190 init/main.c:407
 [<ffffffff84a668a7>] start_kernel+0x679/0x6ae init/main.c:661
 [<ffffffff84a6529d>] x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
 [<ffffffff84a653df>] x86_64_start_kernel+0x140/0x163 arch/x86/kernel/head64.c:177
Code: 
c00 
c0f 
c1f 
c00 
c55 
c65 
c48 
c8b 
c04 
c25 
c40 
c55 
c01 
c00 
c48 
c85 
cc0 
c48 
c89 
ce5 
c74 
c1a 
c65 
c8b 
c15 
ce7 
cd2 
cca 
c7e 
c81 
ce2 
c00 
c01 
c1f 
c00 
c75 
c0b 
c8b 
c90 
c68 
c12 
c00 
c00 
c<83> 
cfa 
c01 
c74 
c02 
c5d 
cc3 
c48 
c8b 
c88 
c70 
c12 
c00 
c00 
c8b 
c80 
c6c 
c12 
c00 
c00 
c48 
c