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SubjectRe: net/sched/act_nat.c BUG
On Fri, Jul 09, 2010 at 05:13:40PM +0200, Eric Dumazet wrote:
> Le vendredi 09 juillet 2010 à 16:37 +0200, Rodrigo Partearroyo González
> a écrit :
> > Hi all,
> >
> > I have been testing Stateless NAT and found that ICMP packets with length less
> > than 20 bytes were not correctly NAT'ed. I have found a BUG that makes taking
> > into account IP header length twice, so ICMP packets smaller than 20 bytes
> > were being dropped.
> >
>
> CC netdev
>
> > The proposed fix is:
> >
> > Index: net/sched/act_nat.c
> > ===================================================================
> > --- net/sched/act_nat.c
> > +++ net/sched/act_nat.c
> > @@ -202,7 +202,7 @@
> > {
> > struct icmphdr *icmph;
> >
> > - if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph)))
> > + if (!pskb_may_pull(skb, ihl + sizeof(*icmph)))
> > goto drop;
> >
> > icmph = (void *)(skb_network_header(skb) + ihl);
> >
> > Please, consider applying it.
>
> Nice catch, but take a look at next lines too,
> when call to skb_clone_writable() is done, since same error is present.
>
> skb_clone_writable(skb,
> ihl + sizeof(*icmph) + sizeof(*iph))
>
> Please submit a formal patch, with your "Signed-off-by: ...", as
> documented in Documentation/SubmittingPatches

No we do need the second IP header, think about it...

However, we should only drop it only if it's long enough and
pskb_may_pull fails.

Thanks,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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