conn *conn_from_freelist() {
    conn *c;

    pthread_mutex_lock(&conn_lock);
    if (freecurr > 0) {
        c = freeconns[--freecurr];
    } else {
        c = NULL;
    }
    pthread_mutex_unlock(&conn_lock);

    return c;
}

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.