netdev - Re: [PATCH net v2] ipv6: add rcu grace period before freeing fib6

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Date:   Mon, 21 Aug 2017 09:19:47 -0700
From:   Wei Wang <weiwan@...gle.com>
To:     David Miller <davem@...emloft.net>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Martin KaFai Lau <kafai@...com>
Subject: Re: [PATCH net v2] ipv6: add rcu grace period before freeing fib6_node

> Goodness.... where to start.
>
> If this bug has been around forever, why did you make this patch
> against net-next instead of net?  (I can tell just by looking at
> the patch because rt6_free_pcpu() is static in 'net' yet it is
> not static in the diff hunk which matches net-next)
>
> And if you made it against net-next, why are you saying "net" in
> your subject line instead of "[PATCH net-next v2]"?
>
> Please sort this out properly, and resubmit.
>
> Thank you.

It should be applied to "net". I will rebase my change and resubmit.
Sorry for the confusion.

Thanks.
Wei

On Sun, Aug 20, 2017 at 7:59 PM, David Miller <davem@...emloft.net> wrote:
> From: Wei Wang <weiwan@...gle.com>
> Date: Sat, 19 Aug 2017 17:34:08 -0700
>
>> From: Wei Wang <weiwan@...gle.com>
>>
>> We currently keep rt->rt6i_node pointing to the fib6_node for the route.
>> And some functions make use of this pointer to dereference the fib6_node
>> from rt structure, e.g. rt6_check(). However, as there is neither
>> refcount nor rcu taken when dereferencing rt->rt6i_node, it could
>> potentially cause crashes as rt->rt6i_node could be set to NULL by other
>> CPUs when doing a route deletion.
>> This patch introduces an rcu grace period before freeing fib6_node and
>> makes sure the functions that dereference it takes rcu_read_lock().
>>
>> Note: there is no "Fixes" tag because this bug was there in a very
>> early stage.
>>
>> Signed-off-by: Wei Wang <weiwan@...gle.com>
>> Acked-by: Eric Dumazet <edumazet@...gle.com>
>> ---
>> v2: removed one extra empty line
>
> Goodness.... where to start.
>
> If this bug has been around forever, why did you make this patch
> against net-next instead of net?  (I can tell just by looking at
> the patch because rt6_free_pcpu() is static in 'net' yet it is
> not static in the diff hunk which matches net-next)
>
> And if you made it against net-next, why are you saying "net" in
> your subject line instead of "[PATCH net-next v2]"?
>
> Please sort this out properly, and resubmit.
>
> Thank you.