int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start) {
        assert(p);
        assert(s);

        return dns_packet_append_raw_string(p, s, strlen(s), start);
}

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.