add_io_cb (engine_uiserver_t uiserver, iocb_data_t *iocbd, gpgme_io_cb_t handler)
{
  gpgme_error_t err;

  TRACE_BEG2 (DEBUG_ENGINE, "engine-uiserver:add_io_cb", uiserver,
              "fd %d, dir %d", iocbd->fd, iocbd->dir);
  err = (*uiserver->io_cbs.add) (uiserver->io_cbs.add_priv,
			      iocbd->fd, iocbd->dir,
			      handler, iocbd->data, &iocbd->tag);
  if (err)
    return TRACE_ERR (err);
  if (!iocbd->dir)
    /* FIXME Kludge around poll() problem.  */
    err = _gpgme_io_set_nonblocking (iocbd->fd);
  return TRACE_ERR (err);
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.