linux-kernel - Re: net/ipv6: GPF in rt6_device

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Date:   Wed, 3 May 2017 20:55:31 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Andrey Konovalov <andreyknvl@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: net/ipv6: GPF in rt6_device_match

On Wed, May 3, 2017 at 7:43 PM, David Ahern <dsahern@...il.com> wrote:
> On 5/3/17 5:35 PM, Cong Wang wrote:
>> Ah, we need:
>>
>> @@ -4024,7 +4027,7 @@ static struct pernet_operations ip6_route_net_late_ops = {
>>
>>  static struct notifier_block ip6_route_dev_notifier = {
>>         .notifier_call = ip6_route_dev_notify,
>> -       .priority = 0,
>> +       .priority = -10, /* Must be called after addrconf_notify!! */
>>  };
>>
>
>
> It's not a notifier problem; the null_entry is created in ip6_route_init
> which is an init function.

Only init_net's null entry is created here.

>
> For network namespaces other than init_net, it is never initialized. See
> ip6_route_net_init.

I don't understand what you are talking about...

It is obviously initialized in 3 places:

1) The template itself, as we use memdup()
2) Code around dst_init_metrics() in ip6_route_net_init()
3) ip6_route_dev_notify(), which is supposed to initialize it after
loopback registers (the order needs to fix, as shown in my patch)

Why not add a printk and play with my patch to see the difference?