q922_string(netdissect_options *ndo, const u_char *p, u_int length)
{

    static u_int dlci, addr_len;
    static uint8_t flags[4];
    static char buffer[sizeof("DLCI xxxxxxxxxx")];
    memset(buffer, 0, sizeof(buffer));

    if (parse_q922_addr(ndo, p, &dlci, &addr_len, flags, length) == 1){
        snprintf(buffer, sizeof(buffer), "DLCI %u", dlci);
    }

    return buffer;
}

The product reads data past the end, or before the beginning, of the intended buffer.