INFO: task syz-executor.0:2141 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.0 D25016 2141 1 0x00000004 ffff8801d26817c0 ffff8801d3030000 ffff8801db621000 ffff8801d3844740 ffff8801db621018 ffff8801a9ab7b28 ffffffff82801a4e ffff8801d26817c0 ffff8801a9ab7c00 0000000000000046 ffff8801db6218f0 1ffff10035356f54 Call Trace: [<00000000fd38f2bb>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000b94b1321>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000b81b6a9c>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000b81b6a9c>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<000000002c9981ed>] __lo_release drivers/block/loop.c:1642 [inline] [<000000002c9981ed>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665 [<00000000337ef04b>] __blkdev_put+0x461/0x840 fs/block_dev.c:1606 [<00000000786865c2>] blkdev_put+0x88/0x560 fs/block_dev.c:1671 [<00000000233a4b86>] blkdev_close+0x8b/0xb0 fs/block_dev.c:1678 [<00000000d3511e5b>] __fput+0x274/0x720 fs/file_table.c:208 [<000000000f36f8cf>] ____fput+0x16/0x20 fs/file_table.c:244 [<00000000465b5546>] task_work_run+0x108/0x180 kernel/task_work.c:116 [<000000000b508158>] tracehook_notify_resume include/linux/tracehook.h:191 [inline] [<000000000b508158>] exit_to_usermode_loop+0x13b/0x160 arch/x86/entry/common.c:162 [<00000000e58f5b43>] prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline] [<00000000e58f5b43>] syscall_return_slowpath arch/x86/entry/common.c:263 [inline] [<00000000e58f5b43>] do_syscall_64+0x3f7/0x570 arch/x86/entry/common.c:290 [<000000007727a1c9>] 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: [<000000004b65d039>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<000000004b65d039>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<00000000b28fcb9d>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 1 lock held by rsyslogd/1922: #0: (&f->f_pos_lock){+.+.+.}, at: [<00000000d20b6785>] __fdget_pos+0xa8/0xd0 fs/file.c:782 2 locks held by getty/2050: #0: (&tty->ldisc_sem){++++++}, at: [<00000000422f39f0>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+...}, at: [<000000009735d287>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 3 locks held by syz-executor.0/2141: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000be442c3b>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<00000000d0e53434>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664 #2: (loop_ctl_mutex#2){+.+.+.}, at: [<000000002c9981ed>] __lo_release drivers/block/loop.c:1642 [inline] #2: (loop_ctl_mutex#2){+.+.+.}, at: [<000000002c9981ed>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665 2 locks held by syz-executor.3/2146: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000bb325dfb>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000afe2571b>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 1 lock held by syz-executor.4/2149: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<0000000029ee293e>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by syz-executor.2/2152: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<0000000029ee293e>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 2 locks held by syz-executor.1/20981: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<0000000029ee293e>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 #1: (&bdev->bd_mutex){+.+.+.}, at: [<00000000e1463cab>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 2 locks held by blkid/20980: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000bb325dfb>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000afe2571b>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 1 lock held by blkid/20987: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<0000000029ee293e>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 2 locks held by blkid/20991: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000bb325dfb>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000afe2571b>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 1 lock held by blkid/20992: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000bb325dfb>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 ============================================= 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: [<00000000dc5a9c0f>] __dump_stack lib/dump_stack.c:15 [inline] [<00000000dc5a9c0f>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<0000000001a50cca>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<000000004334cfa5>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<00000000cf1837ff>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<00000000c0ad03f1>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<00000000c0ad03f1>] check_hung_task kernel/hung_task.c:126 [inline] [<00000000c0ad03f1>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<00000000c0ad03f1>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<00000000fecd0e9c>] kthread+0x278/0x310 kernel/kthread.c:211 [<00000000de138ecf>] 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