netdev - Re: [PATCH net] ipv6: mld: fix add_grhead skb_over

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Date:	Wed, 05 Nov 2014 13:09:13 +0100
From:	Daniel Borkmann <dborkman@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	davem@...emloft.net, lw1a2.jing@...il.com, fw@...len.de,
	hannes@...essinduktion.org, netdev@...r.kernel.org,
	Eric Dumazet <edumazet@...gle.com>,
	David L Stevens <david.stevens@...cle.com>
Subject: Re: [PATCH net] ipv6: mld: fix add_grhead skb_over_panic for devs
 with large MTUs

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: lw1a2.jing@...il.com
>> Fixes: 72e09ad107e7 ("ipv6: avoid high order allocations")
>> Signed-off-by: Daniel Borkmann <dborkman@...hat.com>
>> Cc: Eric Dumazet <edumazet@...gle.com>
>> Cc: David L Stevens <david.stevens@...cle.com>
>> ---
>>   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
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