Subject: Re: [PATCH net] ipv6: mld: fix add_grhead skb_over_panic for devs with large MTUs

From: Daniel Borkmann <[email-masked]>
Date: Wed, 05 Nov 2014 13:09:13 +0100

On 11/05/2014 02:06 AM, Eric Dumazet wrote:
> On Wed, 2014-11-05 at 01:58 +0100, Daniel Borkmann wrote:
>> It has been reported that generating an MLD listener report on
>> devices with large MTUs (e.g. 9000) and a high number of IPv6
>> addresses can trigger a skb_over_panic():
>>
[...]
>>
>> Reported-by: [email-masked]
>> Fixes: 72e09ad107e7 ("ipv6: avoid high order allocations")
>> Signed-off-by: Daniel Borkmann <[email-masked]>
>> Cc: Eric Dumazet <[email-masked]>
>> Cc: David L Stevens <[email-masked]>
>> ---
>>   In skb_nofrag_tailroom(), we could actually omit the !skb->dev check,
>>   but I leave that rather as a possible cleanup item for net-next.

Thanks for your feedback!

> Hmm... we have a proliferation of such things.
>
> Could you take a look at sk_stream_alloc_skb(), skb->reserved_tailroom,
> and skb_availroom() ?

Ok, here would be a proposal based on skb_availroom():

   http://patchwork.ozlabs.org/patch/406959/

Thanks,
Daniel