INFO: task syz-executor2:7417 blocked for more than 140 seconds. Not tainted 4.9.155+ #27 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor2 D28976 7417 2518 0x00000004 ffff8801ae2c4740 ffff8801c827a100 ffff8801db721000 ffff8801cd374740 ffff8801db721018 ffff8801c82cfc48 ffffffff82806806 ffffffff815cc960 0000000000000000 ffff8801ae2c4ff0 0000000000000006 ffff8801db7218f0 Call Trace: [] schedule+0x92/0x1c0 kernel/sched/core.c:3553 [] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3586 [] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [] blkdev_put+0x2b/0x560 fs/block_dev.c:1629 [] blkdev_close+0x8b/0xb0 fs/block_dev.c:1678 [] __fput+0x274/0x720 fs/file_table.c:208 [] ____fput+0x16/0x20 fs/file_table.c:244 [] task_work_run+0x108/0x180 kernel/task_work.c:116 [] tracehook_notify_resume include/linux/tracehook.h:191 [inline] [] exit_to_usermode_loop+0x13b/0x160 arch/x86/entry/common.c:162 [] prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline] [] syscall_return_slowpath arch/x86/entry/common.c:263 [inline] [] do_syscall_64+0x3f7/0x570 arch/x86/entry/common.c:290 [] 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: [] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [] watchdog+0x11b/0xa40 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336 1 lock held by rsyslogd/1906: #0: (&f->f_pos_lock){+.+.+.}, at: [] __fdget_pos+0xa8/0xd0 fs/file.c:781 2 locks held by getty/2034: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+...}, at: [] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 1 lock held by syz-executor2/7417: #0: (&bdev->bd_mutex){+.+.+.}, at: [] blkdev_put+0x2b/0x560 fs/block_dev.c:1629 2 locks held by syz-executor3/7419: #0: (&bdev->bd_mutex){+.+.+.}, at: [] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_ctl_mutex){+.+.+.}, at: [] lo_release+0x1e/0x190 drivers/block/loop.c:1641 1 lock held by syz-executor4/7420: #0: (&bdev->bd_mutex){+.+.+.}, at: [] blkdev_put+0x2b/0x560 fs/block_dev.c:1629 2 locks held by syz-executor0/7440: #0: (loop_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1404 #1: (&bdev->bd_mutex){+.+.+.}, at: [] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.155+ #27 ffff8801d9907cd0 ffffffff81b47871 0000000000000000 0000000000000000 0000000000000000 ffffffff81097301 00000000003fff8e ffff8801d9907d08 ffffffff81b52afc 0000000000000000 0000000000000000 0000000000000000 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [] check_hung_task kernel/hung_task.c:125 [inline] [] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [] watchdog+0x5f7/0xa40 kernel/hung_task.c:239 [] kthread+0x278/0x310 kernel/kthread.c:211 [] 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 0xffffffff82815692