unregister_netdevice: waiting for lo to become free. Usage count = 2 INFO: task syz-executor3:15905 blocked for more than 120 seconds. Not tainted 4.9.40-ged32335 #11 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor3 D28848 15905 9293 0x00000004 ffff8801cf849780 0000000000000000 ffff8801c63ef480 ffff8801da29af00 ffff8801db321498 ffff8801a98af9f8 ffffffff8388f2bb 0000000000000000 0000000000000007 00ff8801cf849780 ffff8801db321db0 ffff8801db321dd8 Call Trace: [] schedule+0x92/0x1b0 kernel/sched/core.c:3624 [] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3657 [] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [] mutex_lock_nested+0x312/0x870 kernel/locking/mutex.c:621 [] copy_net_ns+0x155/0x280 net/core/net_namespace.c:387 [] create_new_namespaces+0x37f/0x730 kernel/nsproxy.c:106 [] copy_namespaces+0x291/0x320 kernel/nsproxy.c:164 [] copy_process.part.50+0x1c99/0x5d40 kernel/fork.c:1658 [] copy_process kernel/fork.c:1482 [inline] [] _do_fork+0x1c0/0xd70 kernel/fork.c:1940 [] SYSC_clone kernel/fork.c:2050 [inline] [] SyS_clone+0x37/0x50 kernel/fork.c:2044 [] do_syscall_64+0x197/0x490 arch/x86/entry/common.c:280 [] entry_SYSCALL64_slow_path+0x25/0x25 Showing all locks held in the system: 2 locks held by khungtaskd/512: #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+0x74/0x290 kernel/locking/lockdep.c:4329 2 locks held by getty/3206: #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 3 locks held by kworker/u4:5/3593: #0: ("%s""netns"){.+.+.+}, at: [] __write_once_size include/linux/compiler.h:272 [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:615 [inline] #0: ("%s""netns"){.+.+.+}, at: [] set_work_pool_and_clear_pending kernel/workqueue.c:642 [inline] #0: ("%s""netns"){.+.+.+}, at: [] process_one_work+0x6a9/0x15f0 kernel/workqueue.c:2089 #1: (net_cleanup_work){+.+.+.}, at: [] process_one_work+0x6db/0x15f0 kernel/workqueue.c:2093 #2: (net_mutex){+.+.+.}, at: [] cleanup_net+0x13f/0x610 net/core/net_namespace.c:420 1 lock held by syz-executor3/15905: #0: (net_mutex){+.+.+.}, at: [] copy_net_ns+0x155/0x280 net/core/net_namespace.c:387 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 512 Comm: khungtaskd Not tainted 4.9.40-ged32335 #11 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801d88ffd00 ffffffff81d8d829 0000000000000000 0000000000000000 0000000000000000 0000000000000001 ffffffff810bd010 ffff8801d88ffd38 ffffffff81d9893d 0000000000000000 0000000000000000 ffff8801cf849b18 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+0x2a/0x40 arch/x86/entry/entry_64.S:433 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff8389f336