static int asymmetric_key_match_preparse(struct key_match_data *match_data)
{
	match_data->lookup_type = KEYRING_SEARCH_LOOKUP_ITERATE;
	match_data->cmp = asymmetric_key_cmp;
	return 0;
}
A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.