netdev - Re: [PATCH 1/2] ipv4: initialize fib_trie prior to register_netdev

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Message-ID: <CAF2d9jgxOPxo9muz0qFcD1+GyidoPavsooeHxvQ3GNqwLWi4LQ@mail.gmail.com>
Date:   Wed, 5 Jul 2017 10:23:06 -0700
From:   Mahesh Bandewar (महेश बंडेवार) 
        <maheshb@...gle.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Mahesh Bandewar <mahesh@...dewar.net>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>,
        David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH 1/2] ipv4: initialize fib_trie prior to
 register_netdev_notifier call.

On Wed, Jul 5, 2017 at 9:24 AM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
> Mahesh Bandewar <mahesh@...dewar.net> writes:
>
>> From: Mahesh Bandewar <maheshb@...gle.com>
>>
>> Net stack initialization currently initializes fib-trie after the
>> first call to netdevice_notifier() call. It does not cause any problem
>> since there are no devices UP at this moment, but trying to bring 'lo'
>> UP at initialization would make this assumption wrong. However changing
>> order solves the issue.
>
> This looks like a real issue and you are part of the way to a real fix.
> The principle being you should not register things notifications until
> you are ready to handle them.
>
> As such fib_trie_init (which allocates the slabs) needs to come before
> rtnl_register.  As a rtnl message can trigger slab allocation.
>
> I have not traced it through but I suspect
> register_pernet_subsys(&fib_net_ops) also needs to come before
> rtnl_register.
>
> Sigh.  It looks like this patch can be labeled:
>
> Fixes: 7b1a74fdbb9e ("[NETNS]: Refactor fib initialization so it can handle multiple namespaces.")
> Fixes: 7f9b80529b8a ("[IPV4]: fib hash|trie initialization")
>
> So I really think the code needs to say:
>
> void __init ip_fib_init(void)
> {
>         fib_trie_init();
>         register_pernet_subsys(&fib_net_ops);
>
>         register_netdevice_notifier(&fib_netdev_notifier);
>         register_inetaddr_notifier(&fib_inetaddr_notifier);
>
>         rtnl_register(PF_INET, RTM_NEWROUTE, inet_rtm_newroute, NULL, NULL);
>         rtnl_register(PF_INET, RTM_DELROUTE, inet_rtm_delroute, NULL, NULL);
>         rtnl_register(PF_INET, RTM_GETROUTE, NULL, inet_dump_fib, NULL);
> }
>
Will update in the next version.

thanks,
--mahesh..
> Eric