unregister_netdevice: waiting for lo to become free. Usage count = 3 INFO: task syz-executor5:16270 blocked for more than 120 seconds. Not tainted 4.9.80-gb30d2b5 #28 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor5 D27856 16270 3884 0x00000002 ffff8801b5a81800 ffff8801b5be4a80 ffff8801b352f9c0 ffff8801b3cfe000 ffff8801db221b98 ffff8801c58d7340 ffffffff838a23db 0000000041b58ab3 ffffffff84193128 00ffffff8123be80 ffff8801db222468 ffff8801db222490 Call Trace: [] schedule+0x7f/0x1b0 kernel/sched/core.c:3550 [] schedule_timeout+0x56c/0x10b0 kernel/time/timer.c:1768 [] io_schedule_timeout+0x1be/0x390 kernel/sched/core.c:5172 [] io_schedule include/linux/sched.h:460 [inline] [] bit_wait_io+0x19/0xa0 kernel/sched/wait.c:582 [] __wait_on_bit_lock+0xc2/0x1c0 kernel/sched/wait.c:421 [] __lock_page+0xff/0x160 mm/filemap.c:934 [] lock_page include/linux/pagemap.h:454 [inline] [] truncate_inode_pages_range+0xc1a/0x12c0 mm/truncate.c:373 [] truncate_inode_pages+0x24/0x30 mm/truncate.c:401 [] kill_bdev+0xbc/0xf0 fs/block_dev.c:96 [] __blkdev_put+0x191/0x7e0 fs/block_dev.c:1586 [] blkdev_put+0x85/0x550 fs/block_dev.c:1663 [] blkdev_close+0x8b/0xb0 fs/block_dev.c:1670 [] __fput+0x28c/0x6e0 fs/file_table.c:208 [] ____fput+0x15/0x20 fs/file_table.c:244 [] task_work_run+0x115/0x190 kernel/task_work.c:116 [] exit_task_work include/linux/task_work.h:21 [inline] [] do_exit+0x7e7/0x2a40 kernel/exit.c:833 [] do_group_exit+0x108/0x320 kernel/exit.c:937 [] get_signal+0x4d4/0x14e0 kernel/signal.c:2317 [] do_signal+0x87/0x1a00 arch/x86/kernel/signal.c:807 [] exit_to_usermode_loop+0xe1/0x120 arch/x86/entry/common.c:156 [] prepare_exit_to_usermode arch/x86/entry/common.c:190 [inline] [] syscall_return_slowpath+0x1a0/0x1e0 arch/x86/entry/common.c:259 [] entry_SYSCALL_64_fastpath+0xe6/0xe8 Showing all locks held in the system: 2 locks held by khungtaskd/513: #0: (rcu_read_lock){......}, at: [] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [] watchdog+0x125/0xa70 kernel/hung_task.c:239 #1: (tasklist_lock){.+.?..}, at: [] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336 2 locks held by getty/3781: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133 4 locks held by kworker/u4:7/10418: #0: ("%s""netns"){.+.+.+}, at: [] work_static include/linux/workqueue.h:186 [inline] #0: ("%s""netns"){.+.+.+}, at: [] set_work_data kernel/workqueue.c:617 [inline] #0: ("%s""netns"){.+.+.+}, at: [] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: ("%s""netns"){.+.+.+}, at: [] process_one_work+0x6f2/0x1610 kernel/workqueue.c:2085 #1: (net_cleanup_work){+.+.+.}, at: [] process_one_work+0x72c/0x1610 kernel/workqueue.c:2089 #2: (net_mutex){+.+.+.}, at: [] cleanup_net+0x13f/0x610 net/core/net_namespace.c:420 #3: (rcu_preempt_state.barrier_mutex){+.+...}, at: [] _rcu_barrier+0x5d/0x330 kernel/rcu/tree.c:3637 1 lock held by syz-executor5/16270: #0: (&bdev->bd_mutex){+.+.+.}, at: [] __blkdev_put+0xbc/0x7e0 fs/block_dev.c:1579 1 lock held by blkid/16279: #0: (&bdev->bd_mutex){+.+.+.}, at: [] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268 1 lock held by syz-executor5/16345: #0: (net_mutex){+.+.+.}, at: [] copy_net_ns+0x155/0x280 net/core/net_namespace.c:387 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 513 Comm: khungtaskd Not tainted 4.9.80-gb30d2b5 #28 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801d8727d00 ffffffff81d94b69 0000000000000000 0000000000000001 0000000000000001 0000000000000001 ffffffff810bac60 ffff8801d8727d38 ffffffff81d9fc8d 0000000000000001 0000000000000000 ffff8801b5df1c18 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99 [] nmi_trigger_cpumask_backtrace+0x117/0x190 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+0x6f0/0xa70 kernel/hung_task.c:239 [] kthread+0x26d/0x300 kernel/kthread.c:211 [] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:477 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff838b20c6