INFO: task syz-executor0:6503 blocked for more than 120 seconds. Not tainted 4.15.0-rc2+ #119 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor0 D24296 6503 21810 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: 0023:0xf7f2bc79 RSP: 002b:00000000f770508c EFLAGS: 00000296 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 000000000000001d RCX: 0000000000004c06 RDX: 000000000000001d 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/673: #0: (rcu_read_lock){....}, at: [<00000000ea78abeb>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000ea78abeb>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<000000004eaa8c3f>] debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554 1 lock held by rsyslogd/2971: #0: (&f->f_pos_lock){+.+.}, at: [<00000000c96e009c>] __fdget_pos+0x131/0x1a0 fs/file.c:770 2 locks held by getty/3053: #0: (&tty->ldisc_sem){++++}, at: [<00000000f8dbc14a>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000072d643f8>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3054: #0: (&tty->ldisc_sem){++++}, at: [<00000000f8dbc14a>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000072d643f8>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3055: #0: (&tty->ldisc_sem){++++}, at: [<00000000f8dbc14a>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000072d643f8>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3056: #0: (&tty->ldisc_sem){++++}, at: [<00000000f8dbc14a>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000072d643f8>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3057: #0: (&tty->ldisc_sem){++++}, at: [<00000000f8dbc14a>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000072d643f8>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3058: #0: (&tty->ldisc_sem){++++}, at: [<00000000f8dbc14a>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000072d643f8>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3059: #0: (&tty->ldisc_sem){++++}, at: [<00000000f8dbc14a>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000072d643f8>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 1 lock held by syz-executor0/6503: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e3fd7152>] lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 1 lock held by syz-executor5/6501: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e3fd7152>] lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 1 lock held by syz-executor5/6521: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e3fd7152>] lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 1 lock held by syz-executor1/6518: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e3fd7152>] lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 1 lock held by syz-executor4/6526: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e3fd7152>] lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 1 lock held by syz-executor4/6536: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e3fd7152>] lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 673 Comm: khungtaskd Not tainted 4.15.0-rc2+ #119 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 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54