INFO: task syz-executor0:12642 blocked for more than 120 seconds. Not tainted 4.15.0-rc8+ #268 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor0 D25520 12642 7715 0x00000004 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/0x1b70 drivers/block/loop.c:1355 __blkdev_driver_ioctl block/ioctl.c:303 [inline] blkdev_ioctl+0x1759/0x1e00 block/ioctl.c:601 block_ioctl+0xde/0x120 fs/block_dev.c:1860 vfs_ioctl fs/ioctl.c:46 [inline] do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692 entry_SYSCALL_64_fastpath+0x29/0xa0 RIP: 0033:0x452e99 RSP: 002b:00007f48d5e76c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f48d5e77700 RCX: 0000000000452e99 RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000013 RBP: 0000000000a2f870 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000 R13: 0000000000a2f7ef R14: 00007f48d5e779c0 R15: 0000000000000001 Showing all locks held in the system: 2 locks held by khungtaskd/746: #0: (rcu_read_lock){....}, at: [<000000005c4b8d71>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<000000005c4b8d71>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<0000000039c9d973>] debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4464 1 lock held by rsyslogd/3506: #0: (&f->f_pos_lock){+.+.}, at: [<00000000cc046c9c>] __fdget_pos+0x12b/0x190 fs/file.c:770 2 locks held by getty/3628: #0: (&tty->ldisc_sem){++++}, at: [<00000000ed5f003e>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000006427b62d>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3629: #0: (&tty->ldisc_sem){++++}, at: [<00000000ed5f003e>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000006427b62d>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3630: #0: (&tty->ldisc_sem){++++}, at: [<00000000ed5f003e>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000006427b62d>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3631: #0: (&tty->ldisc_sem){++++}, at: [<00000000ed5f003e>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000006427b62d>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3632: #0: (&tty->ldisc_sem){++++}, at: [<00000000ed5f003e>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000006427b62d>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3633: #0: (&tty->ldisc_sem){++++}, at: [<00000000ed5f003e>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000006427b62d>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3634: #0: (&tty->ldisc_sem){++++}, at: [<00000000ed5f003e>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000006427b62d>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 1 lock held by syz-executor0/12642: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000fb9fa8b2>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 2 locks held by syz-executor0/12643: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000fb9fa8b2>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 #1: (&bdev->bd_mutex){+.+.}, at: [<00000000b501f5a7>] blkdev_reread_part+0x1e/0x40 block/ioctl.c:192 2 locks held by blkid/12626: #0: (&bdev->bd_mutex){+.+.}, at: [<0000000040889b30>] __blkdev_get+0x158/0x10e0 fs/block_dev.c:1439 #1: (loop_index_mutex){+.+.}, at: [<000000000f2b9e8e>] lo_open+0x1b/0xa0 drivers/block/loop.c:1571 2 locks held by syz-executor6/12640: #0: (loop_index_mutex){+.+.}, at: [<000000009eabff72>] loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1938 #1: (&lo->lo_ctl_mutex#2){+.+.}, at: [<00000000f997eaa0>] loop_control_ioctl+0x1a7/0x490 drivers/block/loop.c:1952 1 lock held by syz-executor6/12644: #0: (loop_index_mutex){+.+.}, at: [<000000009eabff72>] loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1938 1 lock held by syz-executor6/12661: #0: (&bdev->bd_mutex){+.+.}, at: [<0000000040889b30>] __blkdev_get+0x158/0x10e0 fs/block_dev.c:1439 1 lock held by syz-executor6/12664: #0: (loop_index_mutex){+.+.}, at: [<000000009eabff72>] loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1938 1 lock held by syz-executor6/12673: #0: (loop_index_mutex){+.+.}, at: [<000000009eabff72>] loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1938 1 lock held by syz-executor6/12679: #0: (&bdev->bd_mutex){+.+.}, at: [<0000000040889b30>] __blkdev_get+0x158/0x10e0 fs/block_dev.c:1439 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 746 Comm: khungtaskd Not tainted 4.15.0-rc8+ #268 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+0x33c/0x400 kernel/kthread.c:238 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:541 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