arptables: use match, target and data copy_to_user helpers

Convert arptables to copying entries, matches and targets one by one,
using the xt_match_to_user and xt_target_to_user helper functions.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/ipv4/netfilter/arp_tables.c

@@ -677,18 +677,17 @@ static int copy_entries_to_user(unsigned int total_size,
 		return PTR_ERR(counters);
 
 	loc_cpu_entry = private->entries;
-	/* ... then copy entire thing ... */
-	if (copy_to_user(userptr, loc_cpu_entry, total_size) != 0) {
-		ret = -EFAULT;
-		goto free_counters;
-	}
 
 	/* FIXME: use iterator macros --RR */
 	/* ... then go back and fix counters and names */
 	for (off = 0, num = 0; off < total_size; off += e->next_offset, num++){
 		const struct xt_entry_target *t;
 
 		e = (struct arpt_entry *)(loc_cpu_entry + off);
+		if (copy_to_user(userptr + off, e, sizeof(*e))) {
+			ret = -EFAULT;
+			goto free_counters;
+		}
 		if (copy_to_user(userptr + off
 				 + offsetof(struct arpt_entry, counters),
 				 &counters[num],
@@ -698,11 +697,7 @@ static int copy_entries_to_user(unsigned int total_size,
 		}
 
 		t = arpt_get_target_c(e);
-		if (copy_to_user(userptr + off + e->target_offset
-				 + offsetof(struct xt_entry_target,
-					    u.user.name),
-				 t->u.kernel.target->name,
-				 strlen(t->u.kernel.target->name)+1) != 0) {
+		if (xt_target_to_user(t, userptr + off + e->target_offset)) {
 			ret = -EFAULT;
 			goto free_counters;
 		}