netfilter: ipset: fix hash:net,port,net hang with /0 subnet

The hash:net,port,net set type supports /0 subnets. However, the patch
commit 5f7b51b titled "netfilter: ipset: Limit the maximal range
of consecutive elements to add/delete" did not take into account it and
resulted in an endless loop. The bug is actually older but the patch
5f7b51b brings it out earlier.

Handle /0 subnets properly in hash:net,port,net set types.

Fixes: 5f7b51b ("netfilter: ipset: Limit the maximal range of consecutive elements to add/delete")
Reported-by: Марк Коренберг <socketpair@gmail.com>
Signed-off-by: Jozsef Kadlecsik <kadlec@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Author: Jozsef Kadlecsik

net/netfilter/ipset/ip_set_hash_netportnet.c

@@ -173,17 +173,26 @@ hash_netportnet4_kadt(struct ip_set *set, const struct sk_buff *skb,
 	return adtfn(set, &e, &ext, &opt->ext, opt->cmdflags);
 }
 
+static u32
+hash_netportnet4_range_to_cidr(u32 from, u32 to, u8 *cidr)
+{
+	if (from == 0 && to == UINT_MAX) {
+		*cidr = 0;
+		return to;
+	}
+	return ip_set_range_to_cidr(from, to, cidr);
+}
+
 static int
 hash_netportnet4_uadt(struct ip_set *set, struct nlattr *tb[],
 		      enum ipset_adt adt, u32 *lineno, u32 flags, bool retried)
 {
-	const struct hash_netportnet4 *h = set->data;
+	struct hash_netportnet4 *h = set->data;
 	ipset_adtfn adtfn = set->variant->adt[adt];
 	struct hash_netportnet4_elem e = { };
 	struct ip_set_ext ext = IP_SET_INIT_UEXT(set);
 	u32 ip = 0, ip_to = 0, p = 0, port, port_to;
-	u32 ip2_from = 0, ip2_to = 0, ip2, ipn;
-	u64 n = 0, m = 0;
+	u32 ip2_from = 0, ip2_to = 0, ip2, i = 0;
 	bool with_ports = false;
 	int ret;
 
@@ -285,19 +294,6 @@ hash_netportnet4_uadt(struct ip_set *set, struct nlattr *tb[],
 	} else {
 		ip_set_mask_from_to(ip2_from, ip2_to, e.cidr[1]);
 	}
-	ipn = ip;
-	do {
-		ipn = ip_set_range_to_cidr(ipn, ip_to, &e.cidr[0]);
-		n++;
-	} while (ipn++ < ip_to);
-	ipn = ip2_from;
-	do {
-		ipn = ip_set_range_to_cidr(ipn, ip2_to, &e.cidr[1]);
-		m++;
-	} while (ipn++ < ip2_to);
-
-	if (n*m*(port_to - port + 1) > IPSET_MAX_RANGE)
-		return -ERANGE;
 
 	if (retried) {
 		ip = ntohl(h->next.ip[0]);
@@ -310,13 +306,19 @@ hash_netportnet4_uadt(struct ip_set *set, struct nlattr *tb[],
 
 	do {
 		e.ip[0] = htonl(ip);
-		ip = ip_set_range_to_cidr(ip, ip_to, &e.cidr[0]);
+		ip = hash_netportnet4_range_to_cidr(ip, ip_to, &e.cidr[0]);
 		for (; p <= port_to; p++) {
 			e.port = htons(p);
 			do {
+				i++;
 				e.ip[1] = htonl(ip2);
-				ip2 = ip_set_range_to_cidr(ip2, ip2_to,
-							   &e.cidr[1]);
+				if (i > IPSET_MAX_RANGE) {
+					hash_netportnet4_data_next(&h->next,
+								   &e);
+					return -ERANGE;
+				}
+				ip2 = hash_netportnet4_range_to_cidr(ip2,
+							ip2_to, &e.cidr[1]);
 				ret = adtfn(set, &e, &ext, &ext, flags);
 				if (ret && !ip_set_eexist(ret, flags))
 					return ret;