netfilter: nf_tables: fix loop checking with end interval elements

Fix access to uninitialized data for end interval elements. The
element data part is uninitialized in interval end elements.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -2998,6 +2998,9 @@ static int nf_tables_loop_check_setelem(const struct nft_ctx *ctx,
 					const struct nft_set_iter *iter,
 					const struct nft_set_elem *elem)
 {
+	if (elem->flags & NFT_SET_ELEM_INTERVAL_END)
+		return 0;
+
 	switch (elem->data.verdict) {
 	case NFT_JUMP:
 	case NFT_GOTO: