netfilter: nft_compat: check match/targetinfo attr size

We copy according to ->target|matchsize, so check that the netlink attribute
(which can include padding and might be larger) contains enough data.
Reported-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nft_compat.c

@@ -660,6 +660,9 @@ nft_match_select_ops(const struct nft_ctx *ctx,
 	if (IS_ERR(match))
 		return ERR_PTR(-ENOENT);
 
+	if (match->matchsize > nla_len(tb[NFTA_MATCH_INFO]))
+		return ERR_PTR(-EINVAL);
+
 	/* This is the first time we use this match, allocate operations */
 	nft_match = kzalloc(sizeof(struct nft_xt), GFP_KERNEL);
 	if (nft_match == NULL)
@@ -740,6 +743,9 @@ nft_target_select_ops(const struct nft_ctx *ctx,
 	if (IS_ERR(target))
 		return ERR_PTR(-ENOENT);
 
+	if (target->targetsize > nla_len(tb[NFTA_TARGET_INFO]))
+		return ERR_PTR(-EINVAL);
+
 	/* This is the first time we use this target, allocate operations */
 	nft_target = kzalloc(sizeof(struct nft_xt), GFP_KERNEL);
 	if (nft_target == NULL)