INFO: task kworker/u8:9:3506 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:9    state:D stack:24568 pid:3506  tgid:3506  ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: ipv6_addrconf addrconf_dad_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x149b/0x4fd0 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6960
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7017
 __mutex_lock_common kernel/locking/mutex.c:692 [inline]
 __mutex_lock+0x7e6/0x1350 kernel/locking/mutex.c:776
 rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 addrconf_dad_work+0x112/0x14b0 net/ipv6/addrconf.c:4194
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
INFO: task syz.4.284:7055 blocked for more than 149 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.284       state:D stack:27552 pid:7055  tgid:7052  ppid:5831   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x149b/0x4fd0 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6960
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7017
 __mutex_lock_common kernel/locking/mutex.c:692 [inline]
 __mutex_lock+0x7e6/0x1350 kernel/locking/mutex.c:776
 rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 register_netdevice_notifier_net+0x1a/0xa0 net/core/dev.c:2083
 ops_init+0x35c/0x5c0 net/core/net_namespace.c:137
 setup_net+0x110/0x330 net/core/net_namespace.c:446
 copy_net_ns+0x3e3/0x570 net/core/net_namespace.c:581
 create_new_namespaces+0x3e7/0x6a0 kernel/nsproxy.c:130
 unshare_nsproxy_namespaces+0x11c/0x170 kernel/nsproxy.c:226
 ksys_unshare+0x4c8/0x8c0 kernel/fork.c:3171