On Thu, Mar 27, 2014 at 07:32:34PM +0400, Andrey Vagin wrote:
> "len" contains sizeof(nf_ct_ext) and size of extensions. In a worst
> case it can contain all extensions. Bellow you can find sizes for all
> types of extensions. Their sum is definitely bigger than 256.
>
> nf_ct_ext_types[0]->len = 24
> nf_ct_ext_types[1]->len = 32
> nf_ct_ext_types[2]->len = 24
> nf_ct_ext_types[3]->len = 32
> nf_ct_ext_types[4]->len = 152
> nf_ct_ext_types[5]->len = 2
> nf_ct_ext_types[6]->len = 16
> nf_ct_ext_types[7]->len = 8
>
> I have seen "len" up to 280 and my host has crashes w/o this patch.
Very nice catch. I suppose we also need to either increase the size of
offset[] or rearrange the extension so 4 (ECACHE) comes last.
>
> Cc: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
> Cc: Patrick McHardy <kaber@xxxxxxxxx>
> Cc: Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Signed-off-by: Andrey Vagin <avagin@xxxxxxxxxx>
> ---
> include/net/netfilter/nf_conntrack_extend.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/net/netfilter/nf_conntrack_extend.h b/include/net/netfilter/nf_conntrack_extend.h
> index 956b175..36fd6bf 100644
> --- a/include/net/netfilter/nf_conntrack_extend.h
> +++ b/include/net/netfilter/nf_conntrack_extend.h
> @@ -48,7 +48,7 @@ enum nf_ct_ext_id {
> struct nf_ct_ext {
> struct rcu_head rcu;
> u8 offset[NF_CT_EXT_NUM];
> - u8 len;
> + u16 len;
> char data[0];
> };
>
> --
> 1.8.5.3
>
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