netfilter: ipset: Fix warn: integer overflows 'sizeof(*map) + size * set->dsize'

Dan Carpenter reported that the static checker emits the warning

        net/netfilter/ipset/ip_set_list_set.c:600 init_list_set()
        warn: integer overflows 'sizeof(*map) + size * set->dsize'

Limit the maximal number of elements in list type of sets.

Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>

include/linux/netfilter/ipset/ip_set_list.h

@@ -6,5 +6,6 @@
 
 #define IP_SET_LIST_DEFAULT_SIZE	8
 #define IP_SET_LIST_MIN_SIZE		4
+#define IP_SET_LIST_MAX_SIZE		65536
 
 #endif /* __IP_SET_LIST_H */

net/netfilter/ipset/ip_set_list_set.c

@@ -597,7 +597,9 @@ init_list_set(struct net *net, struct ip_set *set, u32 size)
 	struct set_elem *e;
 	u32 i;
 
-	map = kzalloc(sizeof(*map) + size * set->dsize, GFP_KERNEL);
+	map = kzalloc(sizeof(*map) +
+		      min_t(u32, size, IP_SET_LIST_MAX_SIZE) * set->dsize,
+		      GFP_KERNEL);
 	if (!map)
 		return false;