netfilter: ipset: Check IPSET_ATTR_ETHER netlink attribute length

Julia Lawall pointed out that IPSET_ATTR_ETHER netlink attribute length
was not checked explicitly, just for the maximum possible size. Malicious
netlink clients could send shorter attribute and thus resulting a kernel
read after the buffer.

The patch adds the explicit length checkings.
Reported-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>

net/netfilter/ipset/ip_set_bitmap_ipmac.c

@@ -267,6 +267,8 @@ bitmap_ipmac_uadt(struct ip_set *set, struct nlattr *tb[],
 
 	e.id = ip_to_id(map, ip);
 	if (tb[IPSET_ATTR_ETHER]) {
+		if (nla_len(tb[IPSET_ATTR_ETHER]) != ETH_ALEN)
+			return -IPSET_ERR_PROTOCOL;
 		memcpy(e.ether, nla_data(tb[IPSET_ATTR_ETHER]), ETH_ALEN);
 		e.add_mac = 1;
 	}

net/netfilter/ipset/ip_set_hash_mac.c

@@ -110,7 +110,8 @@ hash_mac4_uadt(struct ip_set *set, struct nlattr *tb[],
 	if (tb[IPSET_ATTR_LINENO])
 		*lineno = nla_get_u32(tb[IPSET_ATTR_LINENO]);
 
-	if (unlikely(!tb[IPSET_ATTR_ETHER]))
+	if (unlikely(!tb[IPSET_ATTR_ETHER] ||
+		     nla_len(tb[IPSET_ATTR_ETHER]) != ETH_ALEN))
 		return -IPSET_ERR_PROTOCOL;
 
 	ret = ip_set_get_extensions(set, tb, &ext);