INFO: task syz-executor4:9183 blocked for more than 120 seconds. Not tainted 4.15.0-rc2+ #122 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor4 D25016 9183 3387 0x20020004 Call Trace: context_switch kernel/sched/core.c:2799 [inline] __schedule+0x8eb/0x2060 kernel/sched/core.c:3375 schedule+0xf5/0x430 kernel/sched/core.c:3434 schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3492 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xaad/0x1a80 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 lo_compat_ioctl+0xab/0x140 drivers/block/loop.c:1556 compat_blkdev_ioctl+0x3ba/0x1850 block/compat_ioctl.c:406 C_SYSC_ioctl fs/compat_ioctl.c:1473 [inline] compat_SyS_ioctl+0x151/0x2a30 fs/compat_ioctl.c:1419 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline] do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389 entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125 RIP: 0023:0xf7f17c79 RSP: 002b:00000000f771308c EFLAGS: 00000296 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 0000000000000017 RCX: 0000000000004c04 RDX: 00000000206fdf18 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 Showing all locks held in the system: 2 locks held by khungtaskd/674: #0: (rcu_read_lock){....}, at: [<00000000b175155b>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000b175155b>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<00000000a91b3fb8>] debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554 1 lock held by rsyslogd/3000: #0: (&f->f_pos_lock){+.+.}, at: [<000000003bbb2934>] __fdget_pos+0x131/0x1a0 fs/file.c:770 2 locks held by getty/3122: #0: (&tty->ldisc_sem){++++}, at: [<000000007061dfd6>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000008b883c05>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3123: #0: (&tty->ldisc_sem){++++}, at: [<000000007061dfd6>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000008b883c05>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3124: #0: (&tty->ldisc_sem){++++}, at: [<000000007061dfd6>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000008b883c05>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3125: #0: (&tty->ldisc_sem){++++}, at: [<000000007061dfd6>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000008b883c05>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3126: #0: (&tty->ldisc_sem){++++}, at: [<000000007061dfd6>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000008b883c05>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3127: #0: (&tty->ldisc_sem){++++}, at: [<000000007061dfd6>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000008b883c05>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3128: #0: (&tty->ldisc_sem){++++}, at: [<000000007061dfd6>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000008b883c05>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 1 lock held by syz-executor4/9183: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000a1f763fa>] lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 1 lock held by syz-executor4/9197: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000a1f763fa>] lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 1 lock held by syz-executor4/9217: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000a1f763fa>] lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 674 Comm: khungtaskd Not tainted 4.15.0-rc2+ #122 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x122/0x180 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline] check_hung_task kernel/hung_task.c:132 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline] watchdog+0x90c/0xd60 kernel/hung_task.c:249 kthread+0x37a/0x440 kernel/kthread.c:238 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:441 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0-rc2+ #122 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:tick_irq_enter+0x0/0x390 kernel/time/tick-sched.c:66 RSP: 0018:ffff8801db407d50 EFLAGS: 00000082 RAX: dffffc0000000000 RBX: ffffffff85e2f380 RCX: 0000000000000001 RDX: 1ffffffff0bd9731 RSI: 0000000080000001 RDI: 0000000000000082 RBP: ffff8801db407d60 R08: 0000000000000000 R09: 0000000000000001 R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff85e2f380 R13: 1ffff1003b680fb1 R14: ffff8801db407e68 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8801db400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fb5e7ecc140 CR3: 00000001d4f71000 CR4: 00000000001406f0 DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000020000000 DR3: 0000000020000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 Call Trace: scheduler_ipi+0x246/0x830 kernel/sched/core.c:1793 smp_reschedule_interrupt+0xe6/0x670 arch/x86/kernel/smp.c:277 reschedule_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:819 RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54 RSP: 0018:ffffffff85e07d08 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff02 RAX: dffffc0000000000 RBX: 1ffffffff0bc0fa4 RCX: 0000000000000000 RDX: 1ffffffff0bd9734 RSI: 0000000000000001 RDI: ffffffff85ecb9a0 RBP: ffffffff85e07d08 R08: ffffffff85beaae0 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: ffffffff85e07dc0 R14: ffffffff865eb0a0 R15: 0000000000000000 arch_safe_halt arch/x86/include/asm/paravirt.h:93 [inline] default_idle+0xbf/0x460 arch/x86/kernel/process.c:348 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:339 default_idle_call+0x36/0x90 kernel/sched/idle.c:98 cpuidle_idle_call kernel/sched/idle.c:156 [inline] do_idle+0x24a/0x3b0 kernel/sched/idle.c:246 cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:351 rest_init+0xed/0xf0 init/main.c:435 start_kernel+0x729/0x74f init/main.c:710 x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:378 x86_64_start_kernel+0x77/0x7a arch/x86/kernel/head64.c:359 secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237 Code: ff ff e8 c4 b9 42 00 e9 d6 f9 ff ff 4c 89 ef e8 b7 b9 42 00 e9 c1 fb ff ff 4c 89 e7 e8 aa b9 42 00 e9 29 fd ff ff 0f 1f 44 00 00 <55> 48 89 e5 41 56 41 55 41 54 53 48 c7 c3 40 dc 01 00 e8 99 3e