INFO: task syz-executor5:9366 blocked for more than 120 seconds. Not tainted 4.15.0-rc6-mm1+ #51 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor5 D29392 9366 3698 0x00000004 Call Trace: context_switch kernel/sched/core.c:2800 [inline] __schedule+0x850/0x1e10 kernel/sched/core.c:3376 schedule+0x7c/0x1a0 kernel/sched/core.c:3435 schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3493 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0x7e4/0x1550 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 __blkdev_driver_ioctl block/ioctl.c:303 [inline] blkdev_ioctl+0x1003/0x1910 block/ioctl.c:601 block_ioctl+0xde/0x120 fs/block_dev.c:1859 vfs_ioctl fs/ioctl.c:46 [inline] do_vfs_ioctl+0x190/0xfe0 fs/ioctl.c:686 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692 entry_SYSCALL_64_fastpath+0x23/0x9a RIP: 0033:0x452ac9 RSP: 002b:00007f153936dc58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452ac9 RDX: 0000000000000002 RSI: 0000000000004c08 RDI: 0000000000000013 RBP: 00000000000005c0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f6aa0 R13: 00000000ffffffff R14: 00007f153936e6d4 R15: 0000000000000000 Showing all locks held in the system: 2 locks held by khungtaskd/739: #0: (rcu_read_lock){....}, at: [<00000000943c291e>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000943c291e>] watchdog+0x122/0xab0 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<000000007267dea6>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4464 2 locks held by getty/3438: #0: (&tty->ldisc_sem){++++}, at: [<000000005e558d54>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000002a1def37>] n_tty_read+0x1ec/0x1660 drivers/tty/n_tty.c:2131 2 locks held by getty/3439: #0: (&tty->ldisc_sem){++++}, at: [<000000005e558d54>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000002a1def37>] n_tty_read+0x1ec/0x1660 drivers/tty/n_tty.c:2131 2 locks held by getty/3440: #0: (&tty->ldisc_sem){++++}, at: [<000000005e558d54>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000002a1def37>] n_tty_read+0x1ec/0x1660 drivers/tty/n_tty.c:2131 2 locks held by getty/3441: #0: (&tty->ldisc_sem){++++}, at: [<000000005e558d54>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000002a1def37>] n_tty_read+0x1ec/0x1660 drivers/tty/n_tty.c:2131 2 locks held by getty/3442: #0: (&tty->ldisc_sem){++++}, at: [<000000005e558d54>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000002a1def37>] n_tty_read+0x1ec/0x1660 drivers/tty/n_tty.c:2131 2 locks held by getty/3443: #0: (&tty->ldisc_sem){++++}, at: [<000000005e558d54>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000002a1def37>] n_tty_read+0x1ec/0x1660 drivers/tty/n_tty.c:2131 2 locks held by getty/3444: #0: (&tty->ldisc_sem){++++}, at: [<000000005e558d54>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000002a1def37>] n_tty_read+0x1ec/0x1660 drivers/tty/n_tty.c:2131 1 lock held by syz-executor5/9366: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<000000001a4c2b0a>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor6/9365: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<000000001a4c2b0a>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 739 Comm: khungtaskd Not tainted 4.15.0-rc6-mm1+ #51 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+0x137/0x198 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+0x73d/0xab0 kernel/hung_task.c:249 kthread+0x33c/0x400 kernel/kthread.c:238 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54