INFO: task syz-executor.2:2129 blocked for more than 140 seconds. Not tainted 4.9.170+ #48 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D25016 2129 1 0x00000004 ffff8801d05497c0 0000000000000000 ffff8801db721000 ffff8801da6b2f80 ffff8801db721018 ffff8801a781fa28 ffffffff82801a4e 0000000041b58ab3 ffffffff82e2b9f0 00ffffff81200360 ffff8801db7218f0 1ffff10034f03f34 Call Trace: [<000000006355a7ed>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000803b7117>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000046b0f81>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000046b0f81>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<000000006d44718e>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 [<000000009c1b6a31>] __blkdev_driver_ioctl block/ioctl.c:294 [inline] [<000000009c1b6a31>] blkdev_ioctl+0xe14/0x19e0 block/ioctl.c:590 [<00000000c575221a>] block_ioctl+0xde/0x120 fs/block_dev.c:1696 [<00000000fc539a61>] vfs_ioctl fs/ioctl.c:43 [inline] [<00000000fc539a61>] file_ioctl fs/ioctl.c:493 [inline] [<00000000fc539a61>] do_vfs_ioctl+0xb87/0x11d0 fs/ioctl.c:677 [<000000002e71c02b>] SYSC_ioctl fs/ioctl.c:694 [inline] [<000000002e71c02b>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 [<000000002d2e30c0>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285 [<00000000d5699eb3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb Showing all locks held in the system: 2 locks held by khungtaskd/24: #0: (rcu_read_lock){......}, at: [<00000000e655d908>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<00000000e655d908>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<00000000ad300a3c>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 2 locks held by getty/2037: #0: (&tty->ldisc_sem){++++++}, at: [<000000001fae2f6a>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+...}, at: [<00000000793eb25e>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 1 lock held by syz-executor.2/2129: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<000000006d44718e>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by syz-executor.4/2130: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<000000006d44718e>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by syz-executor.1/2135: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<000000006d44718e>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 3 locks held by syz-executor.3/3753: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000003d48681>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<00000000c922f420>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664 #2: (loop_ctl_mutex#2){+.+.+.}, at: [<000000007b33b69e>] __lo_release drivers/block/loop.c:1642 [inline] #2: (loop_ctl_mutex#2){+.+.+.}, at: [<000000007b33b69e>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665 1 lock held by syz-executor.0/7714: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<000000006d44718e>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by blkid/9813: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<000000006d44718e>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 2 locks held by syz-executor.5/9818: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<000000006d44718e>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 #1: (&bdev->bd_mutex){+.+.+.}, at: [<000000003c504b22>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 1 lock held by blkid/9820: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c23f6aaa>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by blkid/9822: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c23f6aaa>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000003241d9d2>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.170+ #48 ffff8801d98d7cc8 ffffffff81b4fb21 0000000000000000 0000000000000000 0000000000000000 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00 ffffffff81b5adbc 0000000000000000 0000000000000000 0000000000000000 Call Trace: [<00000000cb683e1b>] __dump_stack lib/dump_stack.c:15 [inline] [<00000000cb683e1b>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<00000000cabe5b46>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<0000000094618bc7>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<0000000096030af6>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<00000000590cd0df>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<00000000590cd0df>] check_hung_task kernel/hung_task.c:126 [inline] [<00000000590cd0df>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<00000000590cd0df>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<00000000a543386b>] kthread+0x278/0x310 kernel/kthread.c:211 [<00000000606efc41>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff82810ac2