INFO: task syz-executor.5:7210 blocked for more than 140 seconds. Not tainted 4.9.168+ #39 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D27784 7210 2125 0x80000002 ffff8801d8455f00 0000000000000000 ffff8801db721000 ffff8801a2328000 ffff8801db721018 ffff8801cbe4f7d8 ffffffff8280028e ffff8801cbe4f748 ffffffff81bb5b9c 00ffffff8280fe2a ffff8801db7218f0 1ffff100397c9eea Call Trace: [<0000000001439cb5>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<000000006c9eee2c>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<0000000017650371>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<0000000017650371>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<000000002d1b7343>] blkdev_put+0x2b/0x560 fs/block_dev.c:1629 [<000000004fc182cd>] blkdev_close+0x8b/0xb0 fs/block_dev.c:1678 [<00000000e1b2e296>] __fput+0x274/0x720 fs/file_table.c:208 [<00000000508ab6e8>] ____fput+0x16/0x20 fs/file_table.c:244 [<00000000c27ad812>] task_work_run+0x108/0x180 kernel/task_work.c:116 [<00000000fad701ab>] exit_task_work include/linux/task_work.h:21 [inline] [<00000000fad701ab>] do_exit+0x78b/0x2aa0 kernel/exit.c:841 [<00000000bd76271c>] do_group_exit+0x111/0x300 kernel/exit.c:945 [<00000000053226f9>] get_signal+0x348/0x1aa0 kernel/signal.c:2380 [<00000000e380b1b8>] do_signal+0x9c/0x1920 arch/x86/kernel/signal.c:807 [<000000000b1e1edc>] exit_to_usermode_loop+0x11c/0x160 arch/x86/entry/common.c:158 [<0000000052b9c3e9>] prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline] [<0000000052b9c3e9>] syscall_return_slowpath arch/x86/entry/common.c:263 [inline] [<0000000052b9c3e9>] do_syscall_64+0x3f7/0x570 arch/x86/entry/common.c:290 [<00000000ec4bf6de>] 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: [<0000000039ee8f94>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [<0000000039ee8f94>] watchdog+0x13c/0xae0 kernel/hung_task.c:239 #1: (tasklist_lock){.+.?..}, at: [<00000000feade072>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 2 locks held by getty/2026: #0: (&tty->ldisc_sem){++++++}, at: [<00000000b3d01420>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+...}, at: [<00000000aeec62fa>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 1 lock held by syz-executor.5/7210: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000002d1b7343>] blkdev_put+0x2b/0x560 fs/block_dev.c:1629 1 lock held by syz-executor.5/11149: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000002d1b7343>] blkdev_put+0x2b/0x560 fs/block_dev.c:1629 2 locks held by syz-executor.3/13655: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000037a75aca>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000ab54918c>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.0/15405: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000037a75aca>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000ab54918c>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.5/20519: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000a8a8edf8>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<00000000c3b94d9e>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664 1 lock held by syz-executor.2/13474: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000002d1b7343>] blkdev_put+0x2b/0x560 fs/block_dev.c:1629 1 lock held by syz-executor.5/25228: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000002d1b7343>] blkdev_put+0x2b/0x560 fs/block_dev.c:1629 3 locks held by syz-executor.5/29213: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000a8a8edf8>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<00000000c3b94d9e>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664 #2: (loop_ctl_mutex#2){+.+.+.}, at: [<00000000fb88bef6>] __lo_release drivers/block/loop.c:1642 [inline] #2: (loop_ctl_mutex#2){+.+.+.}, at: [<00000000fb88bef6>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665 2 locks held by syz-executor.2/29232: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<000000009177db12>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 #1: (&bdev->bd_mutex){+.+.+.}, at: [<00000000a73f8fba>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 1 lock held by syz-executor.2/29242: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000037a75aca>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by blkid/29236: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000037a75aca>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000ab54918c>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.168+ #39 ffff8801d98d7cc8 ffffffff81b4f5d1 0000000000000001 0000000000000000 0000000000000001 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00 ffffffff81b5a86c 0000000000000001 0000000000000000 0000000000000001 Call Trace: [<00000000f9b386b6>] __dump_stack lib/dump_stack.c:15 [inline] [<00000000f9b386b6>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<0000000010da3a01>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<00000000a7dc7fef>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<000000008c458e2a>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<000000005ee7d452>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<000000005ee7d452>] check_hung_task kernel/hung_task.c:125 [inline] [<000000005ee7d452>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [<000000005ee7d452>] watchdog+0x661/0xae0 kernel/hung_task.c:239 [<000000001ac0c819>] kthread+0x278/0x310 kernel/kthread.c:211 [<0000000083cf951a>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff8280f302