netfilter: nft_set_pipapo: Actually validate intervals in fields after the first one

Embarrassingly, nft_pipapo_insert() checked for interval validity in
the first field only.

The start_p and end_p pointers were reset to key data from the first
field at every iteration of the loop which was supposed to go over
the set fields.

Fixes: 3c4287f6 ("nf_tables: Add set type for arbitrary concatenation of ranges")
Reported-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nft_set_pipapo.c

@@ -1162,6 +1162,7 @@ static int nft_pipapo_insert(const struct net *net, const struct nft_set *set,
 	struct nft_pipapo_match *m = priv->clone;
 	u8 genmask = nft_genmask_next(net);
 	struct nft_pipapo_field *f;
+	const u8 *start_p, *end_p;
 	int i, bsize_max, err = 0;
 
 	if (nft_set_ext_exists(ext, NFT_SET_EXT_KEY_END))
@@ -1202,9 +1203,9 @@ static int nft_pipapo_insert(const struct net *net, const struct nft_set *set,
 	}
 
 	/* Validate */
+	start_p = start;
+	end_p = end;
 	nft_pipapo_for_each_field(f, i, m) {
-		const u8 *start_p = start, *end_p = end;
-
 		if (f->rules >= (unsigned long)NFT_PIPAPO_RULE0_MAX)
 			return -ENOSPC;