int fsck_walk(struct object *obj, void *data, struct fsck_options *options)
{
	if (!obj)
		return -1;

	if (obj->type == OBJ_NONE)
		parse_object(&obj->oid);

	switch (obj->type) {
	case OBJ_BLOB:
		return 0;
	case OBJ_TREE:
		return fsck_walk_tree((struct tree *)obj, data, options);
	case OBJ_COMMIT:
		return fsck_walk_commit((struct commit *)obj, data, options);
	case OBJ_TAG:
		return fsck_walk_tag((struct tag *)obj, data, options);
	default:
		error("Unknown object type for %s", describe_object(options, obj));
		return -1;
	}
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.