unregister_netdevice: waiting for syz6 to become free. Usage count = 1 INFO: task kworker/u4:3:347 blocked for more than 120 seconds. Not tainted 4.13.0-rc3+ #15 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/u4:3 D11600 347 2 0x00000000 Workqueue: netns cleanup_net Call Trace: context_switch kernel/sched/core.c:2771 [inline] __schedule+0x8e8/0x2070 kernel/sched/core.c:3332 schedule+0x108/0x440 kernel/sched/core.c:3391 schedule_timeout+0x1ce/0x250 kernel/time/timer.c:1688 wait_woken+0x10f/0x280 kernel/sched/wait.c:363 rtnl_lock_unregistering net/core/dev.c:8572 [inline] default_device_exit_batch+0x2ab/0x5d0 net/core/dev.c:8599 ops_exit_list.isra.6+0x100/0x150 net/core/net_namespace.c:145 cleanup_net+0x5c7/0xb50 net/core/net_namespace.c:483 process_one_work+0xbf3/0x1bc0 kernel/workqueue.c:2097 worker_thread+0x223/0x1860 kernel/workqueue.c:2231 kthread+0x35e/0x430 kernel/kthread.c:231 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:425 Showing all locks held in the system: 3 locks held by kworker/u4:3/347: #0: ("%s""netns"){.+.+.+}, at: [] __write_once_size include/linux/compiler.h:279 [inline] #0: ("%s""netns"){.+.+.+}, at: [] atomic64_set arch/x86/include/asm/atomic64_64.h:33 [inline] #0: ("%s""netns"){.+.+.+}, at: [] atomic_long_set include/asm-generic/atomic-long.h:56 [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+0xadf/0x1bc0 kernel/workqueue.c:2090 #1: (net_cleanup_work){+.+.+.}, at: [] process_one_work+0xb32/0x1bc0 kernel/workqueue.c:2094 #2: (net_mutex){+.+.+.}, at: [] cleanup_net+0x247/0xb50 net/core/net_namespace.c:449 2 locks held by khungtaskd/553: #0: (rcu_read_lock){......}, at: [] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){......}, at: [] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.?.+..}, at: [] debug_show_all_locks+0xd2/0x410 kernel/locking/lockdep.c:4417 2 locks held by getty/2883: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/2884: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/2885: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/2886: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/2887: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/2888: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/2889: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2133 1 lock held by syz-executor2/26343: #0: (net_mutex){+.+.+.}, at: [] copy_net_ns+0x239/0x580 net/core/net_namespace.c:409 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 553 Comm: khungtaskd Not tainted 4.13.0-rc3+ #15 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:16 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:52 nmi_cpu_backtrace+0x20e/0x240 lib/nmi_backtrace.c:102 nmi_trigger_cpumask_backtrace+0x122/0x180 lib/nmi_backtrace.c:61 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 trigger_all_cpu_backtrace include/linux/nmi.h:105 [inline] check_hung_task kernel/hung_task.c:132 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline] watchdog+0x90c/0xd60 kernel/hung_task.c:249 kthread+0x35e/0x430 kernel/kthread.c:231 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:425 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff8449c426