unregister_netdevice: waiting for lo to become free. Usage count = 1 unregister_netdevice: waiting for lo to become free. Usage count = 1 unregister_netdevice: waiting for lo to become free. Usage count = 1 unregister_netdevice: waiting for lo to become free. Usage count = 1 unregister_netdevice: waiting for lo to become free. Usage count = 1 INFO: task syz-executor6:23396 blocked for more than 120 seconds. Not tainted 4.16.0+ #1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor6 D21704 23396 4447 0x80000002 Call Trace: context_switch kernel/sched/core.c:2848 [inline] __schedule+0x807/0x1e40 kernel/sched/core.c:3490 schedule+0xef/0x430 kernel/sched/core.c:3549 __rwsem_down_write_failed_common+0x919/0x15d0 kernel/locking/rwsem-xadd.c:566 rwsem_down_write_failed+0xe/0x10 kernel/locking/rwsem-xadd.c:595 call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:117 __down_write arch/x86/include/asm/rwsem.h:142 [inline] down_write+0xa2/0x120 kernel/locking/rwsem.c:72 unregister_netdevice_notifier+0x98/0x520 net/core/dev.c:1698 bcm_release+0x93/0x5c0 net/can/bcm.c:1507 sock_release+0x96/0x1b0 net/socket.c:594 sock_close+0x16/0x20 net/socket.c:1149 __fput+0x34d/0x890 fs/file_table.c:209 ____fput+0x15/0x20 fs/file_table.c:243 task_work_run+0x1e4/0x290 kernel/task_work.c:113 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0x1aee/0x2730 kernel/exit.c:865 do_group_exit+0x16f/0x430 kernel/exit.c:968 get_signal+0x886/0x1960 kernel/signal.c:2469 do_signal+0x90/0x2020 arch/x86/kernel/signal.c:810 exit_to_usermode_loop+0x28a/0x310 arch/x86/entry/common.c:162 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline] syscall_return_slowpath arch/x86/entry/common.c:265 [inline] do_syscall_64+0x792/0x9d0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x4552d9 RSP: 002b:00007f5592b6ace8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: fffffffffffffe00 RBX: 000000000072c1a8 RCX: 00000000004552d9 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000072c1a8 RBP: 000000000072c1a8 R08: 0000000000000000 R09: 000000000072c180 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000a3e81f R14: 00007f5592b6b9c0 R15: 0000000000000004 Showing all locks held in the system: 2 locks held by khungtaskd/877: #0: 000000008a18bbf7 (rcu_read_lock){....}, at: check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: 000000008a18bbf7 (rcu_read_lock){....}, at: watchdog+0x1ff/0xf60 kernel/hung_task.c:249 #1: 00000000124fd837 (tasklist_lock){.+.+}, at: debug_show_all_locks+0xde/0x34a kernel/locking/lockdep.c:4470 1 lock held by rsyslogd/4275: #0: 00000000e79e9e34 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x1a9/0x1e0 fs/file.c:766 2 locks held by getty/4365: #0: 00000000d1a76726 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000ff21dfb7 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4366: #0: 0000000094445c49 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000ae9cf7e7 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4367: #0: 000000006572bb30 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 0000000035223bcd (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4368: #0: 00000000cfeebba4 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000e2bb6bf2 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4369: #0: 000000005066edf4 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000cf4ee9f5 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4370: #0: 000000008099d25d (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000a267e5a8 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4371: #0: 0000000038509230 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 000000007e9de329 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 4 locks held by kworker/u4:4/5719: #0: 00000000e2763f21 ((wq_completion)"%s""netns"){+.+.}, at: __write_once_size include/linux/compiler.h:215 [inline] #0: 00000000e2763f21 ((wq_completion)"%s""netns"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: 00000000e2763f21 ((wq_completion)"%s""netns"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline] #0: 00000000e2763f21 ((wq_completion)"%s""netns"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:57 [inline] #0: 00000000e2763f21 ((wq_completion)"%s""netns"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline] #0: 00000000e2763f21 ((wq_completion)"%s""netns"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: 00000000e2763f21 ((wq_completion)"%s""netns"){+.+.}, at: process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116 #1: 0000000020cebe73 (net_cleanup_work){+.+.}, at: process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120 #2: 0000000036044afd (pernet_ops_rwsem){++++}, at: cleanup_net+0x11a/0xb20 net/core/net_namespace.c:490 #3: 0000000099b72581 (rcu_sched_state.barrier_mutex){+.+.}, at: _rcu_barrier+0x142/0x770 kernel/rcu/tree.c:3495 1 lock held by syz-executor6/23396: #0: 0000000036044afd (pernet_ops_rwsem){++++}, at: unregister_netdevice_notifier+0x98/0x520 net/core/dev.c:1698 1 lock held by syz-executor6/23403: #0: 0000000036044afd (pernet_ops_rwsem){++++}, at: copy_net_ns+0x297/0x4c0 net/core/net_namespace.c:432 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 877 Comm: khungtaskd Not tainted 4.16.0+ #1 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x1b9/0x29f lib/dump_stack.c:53 nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline] check_hung_task kernel/hung_task.c:132 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline] watchdog+0xc10/0xf60 kernel/hung_task.c:249 kthread+0x345/0x410 kernel/kthread.c:238 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:411 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54