Return proper sys_munmap() error code

--- linux-2.2.25/mm/mremap.c~	Wed Feb 18 17:39:06 2004
+++ linux-2.2.25/mm/mremap.c	Wed Feb 18 17:39:06 2004
@@ -176,9 +176,11 @@
 	 * Always allow a shrinking remap: that just unmaps
 	 * the unnecessary pages..
 	 */
-	ret = addr;
 	if (old_len >= new_len) {
-		do_munmap(addr+new_len, old_len - new_len);
+		ret = do_munmap(addr+new_len, old_len - new_len);
+		if (ret && old_len != new_len)
+			goto out;
+		ret = addr;
 		goto out;
 	}