Commit d214c753 authored by Pablo Neira Ayuso's avatar Pablo Neira Ayuso Committed by David S. Miller

filter: add SKF_AD_NLATTR_NEST to look for nested attributes

SKF_AD_NLATTR allows us to find the first matching attribute in a
stream of netlink attributes from one offset to the end of the
netlink message. This is not suitable to look for a specific
matching inside a set of nested attributes.

For example, in ctnetlink messages, if we look for the CTA_V6_SRC
attribute in a message that talks about an IPv4 connection,
SKF_AD_NLATTR returns the offset of CTA_STATUS which has the same
value of CTA_V6_SRC but outside the nest. To differenciate
CTA_STATUS and CTA_V6_SRC, we would have to make assumptions on the
size of the attribute and the usual offset, resulting in horrible
BSF code.

This patch adds SKF_AD_NLATTR_NEST, which is a variant of
SKF_AD_NLATTR, that looks for an attribute inside the limits of
a nested attributes, but not further.

This patch validates that we have enough room to look for the
nested attributes - based on a suggestion from Patrick McHardy.
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
Acked-by: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 68fd9910
...@@ -122,7 +122,8 @@ struct sock_fprog /* Required for SO_ATTACH_FILTER. */ ...@@ -122,7 +122,8 @@ struct sock_fprog /* Required for SO_ATTACH_FILTER. */
#define SKF_AD_PKTTYPE 4 #define SKF_AD_PKTTYPE 4
#define SKF_AD_IFINDEX 8 #define SKF_AD_IFINDEX 8
#define SKF_AD_NLATTR 12 #define SKF_AD_NLATTR 12
#define SKF_AD_MAX 16 #define SKF_AD_NLATTR_NEST 16
#define SKF_AD_MAX 20
#define SKF_NET_OFF (-0x100000) #define SKF_NET_OFF (-0x100000)
#define SKF_LL_OFF (-0x200000) #define SKF_LL_OFF (-0x200000)
......
...@@ -319,6 +319,25 @@ unsigned int sk_run_filter(struct sk_buff *skb, struct sock_filter *filter, int ...@@ -319,6 +319,25 @@ unsigned int sk_run_filter(struct sk_buff *skb, struct sock_filter *filter, int
A = 0; A = 0;
continue; continue;
} }
case SKF_AD_NLATTR_NEST: {
struct nlattr *nla;
if (skb_is_nonlinear(skb))
return 0;
if (A > skb->len - sizeof(struct nlattr))
return 0;
nla = (struct nlattr *)&skb->data[A];
if (nla->nla_len > A - skb->len)
return 0;
nla = nla_find_nested(nla, X);
if (nla)
A = (void *)nla - (void *)skb->data;
else
A = 0;
continue;
}
default: default:
return 0; return 0;
} }
......
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