unregister_netdevice: waiting for lo to become free. Usage count = 3 unregister_netdevice: waiting for lo to become free. Usage count = 3 unregister_netdevice: waiting for lo to become free. Usage count = 3 unregister_netdevice: waiting for lo to become free. Usage count = 3 unregister_netdevice: waiting for lo to become free. Usage count = 3 INFO: task syz-executor6:15527 blocked for more than 120 seconds. Not tainted 4.9.93-gf6bec4e #4 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor6 D28760 15527 1 0x00000004 ffff8801d858c800 0000000000000000 ffff8801d0442f40 ffff8801d69cb000 ffff8801db321b98 ffff8801d972fbc8 ffffffff838c4a7d ffff8801d858d0c0 ffffed003b0b1a17 ffff8801d858c800 00fffc0000000000 ffff8801db322468 Call Trace: [] schedule+0x7f/0x1b0 kernel/sched/core.c:3556 [] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3589 [] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621 [] copy_net_ns+0x155/0x290 net/core/net_namespace.c:387 [] create_new_namespaces+0x51c/0x730 kernel/nsproxy.c:106 [] unshare_nsproxy_namespaces+0xa5/0x1d0 kernel/nsproxy.c:205 [] SYSC_unshare kernel/fork.c:2244 [inline] [] SyS_unshare+0x319/0x710 kernel/fork.c:2194 [] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282 [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb Showing all locks held in the system: 2 locks held by khungtaskd/515: #0: (rcu_read_lock){......}, at: [] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [] watchdog+0x11c/0xa20 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336 1 lock held by rsyslogd/3648: #0: (&f->f_pos_lock){+.+.+.}, at: [] __fdget_pos+0xac/0xd0 fs/file.c:781 2 locks held by getty/3744: #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+0x202/0x16b0 drivers/tty/n_tty.c:2133 3 locks held by kworker/u4:4/4091: #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+0x6ee/0x1500 kernel/workqueue.c:2085 #1: (net_cleanup_work){+.+.+.}, at: [] process_one_work+0x728/0x1500 kernel/workqueue.c:2089 #2: (net_mutex){+.+.+.}, at: [] cleanup_net+0x13f/0x630 net/core/net_namespace.c:420 1 lock held by syz-executor6/15527: #0: (net_mutex){+.+.+.}, at: [] copy_net_ns+0x155/0x290 net/core/net_namespace.c:387 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 515 Comm: khungtaskd Not tainted 4.9.93-gf6bec4e #4 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801d8527d08 ffffffff81d9c299 0000000000000000 0000000000000001 0000000000000001 0000000000000001 ffffffff810b7d90 ffff8801d8527d40 ffffffff81da75d7 0000000000000001 0000000000000000 0000000000000002 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99 [] nmi_trigger_cpumask_backtrace+0x12a/0x14f 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+0x6b4/0xa20 kernel/hung_task.c:239 [] kthread+0x26d/0x300 kernel/kthread.c:211 [] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff838d4586