INFO: task syz-executor.0:11839 blocked for more than 140 seconds. Not tainted 4.9.194+ #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D27800 11839 7793 0x80000002 0000000000000083 ffff8801a0da8000 0000000000000000 ffff8801db621000 ffffffff83031180 ffff8801db621018 ffff8801a05bf7d8 ffffffff8281af8e ffff8801a05bf728 ffffffff8120ced5 00ff8801db61e8c0 ffff8801db6218f0 Call Trace: [<000000002481dbbb>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<0000000003801b6e>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<000000006ca4a8e0>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<000000006ca4a8e0>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<0000000038155a0a>] blkdev_put+0x2b/0x560 fs/block_dev.c:1629 [<0000000040425c05>] blkdev_close+0x8b/0xb0 fs/block_dev.c:1678 [<00000000d316ccc2>] __fput+0x274/0x720 fs/file_table.c:208 [<000000006365c2ac>] ____fput+0x16/0x20 fs/file_table.c:244 [<0000000004f73a36>] task_work_run+0x108/0x180 kernel/task_work.c:116 [<0000000085832517>] exit_task_work include/linux/task_work.h:21 [inline] [<0000000085832517>] do_exit+0x78f/0x2aa0 kernel/exit.c:842 [<00000000251326c7>] do_group_exit+0x111/0x300 kernel/exit.c:946 [<00000000eca0c152>] get_signal+0x377/0x1cb0 kernel/signal.c:2395 [<0000000080b0aa7e>] do_signal+0x9c/0x1920 arch/x86/kernel/signal.c:812 [<00000000a5e8cac1>] exit_to_usermode_loop+0x11c/0x160 arch/x86/entry/common.c:159 [<00000000e8837f08>] prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline] [<00000000e8837f08>] syscall_return_slowpath arch/x86/entry/common.c:266 [inline] [<00000000e8837f08>] do_syscall_64+0x3ab/0x5c0 arch/x86/entry/common.c:293 [<000000000ab23978>] 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: [<000000007d86062b>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<000000007d86062b>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<000000006a6bfc3c>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336 2 locks held by getty/2020: #0: (&tty->ldisc_sem){++++++}, at: [<00000000201e7c21>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+...}, at: [<000000007c56fb8f>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 1 lock held by syz-executor.0/11839: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000038155a0a>] blkdev_put+0x2b/0x560 fs/block_dev.c:1629 2 locks held by syz-executor.5/14423: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000df5dd8a2>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000008a49bc58>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 2 locks held by syz-executor.4/14877: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000df5dd8a2>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000008a49bc58>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 2 locks held by syz-executor.3/18279: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000df5dd8a2>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000008a49bc58>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 2 locks held by syz-executor.2/18282: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000df5dd8a2>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000008a49bc58>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 2 locks held by syz-executor.0/18964: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<00000000fb5bd5d1>] lo_ioctl+0x8e/0x1b10 drivers/block/loop.c:1404 #1: (&bdev->bd_mutex){+.+.+.}, at: [<000000002b39b44e>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 1 lock held by syz-executor.0/18978: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000df5dd8a2>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by syz-executor.1/18963: #0: (loop_index_mutex){+.+.+.}, at: [<00000000db26e682>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1973 #1: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<00000000d7fb6982>] loop_control_ioctl+0x17f/0x320 drivers/block/loop.c:1987 1 lock held by syz-executor.1/18970: #0: (loop_index_mutex){+.+.+.}, at: [<00000000db26e682>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1973 1 lock held by syz-executor.1/18976: #0: (loop_index_mutex){+.+.+.}, at: [<00000000db26e682>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1973 1 lock held by syz-executor.1/18979: #0: (loop_index_mutex){+.+.+.}, at: [<00000000db26e682>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1973 2 locks held by blkid/18968: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000df5dd8a2>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000008a49bc58>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.194+ #0 ffff8801d98d7cc8 ffffffff81b67001 0000000000000000 0000000000000000 0000000000000000 ffffffff81099d01 dffffc0000000000 ffff8801d98d7d00 ffffffff81b7229c 0000000000000000 0000000000000000 0000000000000000 Call Trace: [<000000004f151447>] __dump_stack lib/dump_stack.c:15 [inline] [<000000004f151447>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<00000000ab2b2418>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<000000001432f4c3>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<00000000cf5eaf63>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<000000004aaf8dd0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<000000004aaf8dd0>] check_hung_task kernel/hung_task.c:126 [inline] [<000000004aaf8dd0>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<000000004aaf8dd0>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<000000007f1a719a>] kthread+0x278/0x310 kernel/kthread.c:211 [<0000000052829bac>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:375 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff8282a0e1