netfilter: nf_tables: set names cannot be larger than 15 bytes

Currently, nf_tables trims off the set name if it exceeeds 15
bytes, so explicitly reject set names that are too large.
Reported-by: Giuseppe Longo <giuseppelng@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -1946,7 +1946,8 @@ static const struct nft_set_ops *nft_select_set_ops(const struct nlattr * const
 
 static const struct nla_policy nft_set_policy[NFTA_SET_MAX + 1] = {
 	[NFTA_SET_TABLE]		= { .type = NLA_STRING },
-	[NFTA_SET_NAME]			= { .type = NLA_STRING },
+	[NFTA_SET_NAME]			= { .type = NLA_STRING,
+					    .len = IFNAMSIZ - 1 },
 	[NFTA_SET_FLAGS]		= { .type = NLA_U32 },
 	[NFTA_SET_KEY_TYPE]		= { .type = NLA_U32 },
 	[NFTA_SET_KEY_LEN]		= { .type = NLA_U32 },