unregister_netdevice: waiting for lo to become free. Usage count = 2 INFO: task syz-executor5:15779 blocked for more than 120 seconds. Not tainted 4.9.44-g6dda7ac #31 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor5 D29088 15779 3673 0x00000004 ffff8801d12b4800 0000000000000000 ffff8801aac45500 ffffffff84426880 ffff8801db221518 ffff8801abb279f8 ffffffff838953db 0000000000000246 ffff8801d12b4800 0000000000000000 ffff8801db221e40 ffff8801db221e68 Call Trace: [] schedule+0x92/0x1b0 kernel/sched/core.c:3625 [] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3658 [] __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 INFO: lockdep is turned off. NMI backtrace for cpu 1 CPU: 1 PID: 514 Comm: khungtaskd Not tainted 4.9.44-g6dda7ac #31 unregister_netdevice: waiting for lo to become free. Usage count = 2 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801d8917d00 ffffffff81d929c9 0000000000000000 0000000000000001 0000000000000001 0000000000000001 ffffffff810bd020 ffff8801d8917d38 ffffffff81d9dadd 0000000000000001 0000000000000000 ffff8801d12b4c18 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 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff838a5456 Kernel panic - not syncing: hung_task: blocked tasks CPU: 1 PID: 514 Comm: khungtaskd Not tainted 4.9.44-g6dda7ac #31 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801d8917cb8 ffffffff81d929c9 ffffffff83a899e0 ffff8801d8917d90 ffff8801d12b4c00 dffffc0000000000 ffffffff84409000 ffff8801d8917d80 ffffffff8142e101 0000000041b58ab3 ffffffff84184170 ffffffff8142df45 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] panic+0x1bc/0x3a8 kernel/panic.c:179 [] check_hung_task kernel/hung_task.c:126 [inline] [] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [] watchdog+0x701/0xa70 kernel/hung_task.c:239 [] kthread+0x26d/0x300 kernel/kthread.c:211 [] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433 Dumping ftrace buffer: (ftrace buffer empty) Kernel Offset: disabled Rebooting in 86400 seconds..