logger_get_filename (struct t_gui_buffer *buffer)
{
    char *res, *mask_expanded, *file_path;
    const char *mask;
    const char *dir_separator, *weechat_dir;
    int length;

    res = NULL;
    mask_expanded = NULL;
    file_path = NULL;

    dir_separator = weechat_info_get ("dir_separator", "");
    if (!dir_separator)
        return NULL;
    weechat_dir = weechat_info_get ("weechat_dir", "");
    if (!weechat_dir)
        return NULL;

    /* get filename mask for buffer */
    mask = logger_get_mask_for_buffer (buffer);
    if (!mask)
    {
        weechat_printf_date_tags (
            NULL, 0, "no_log",
            _("%s%s: unable to find filename mask for buffer "
              "\"%s\", logging is disabled for this buffer"),
            weechat_prefix ("error"), LOGGER_PLUGIN_NAME,
            weechat_buffer_get_string (buffer, "name"));
        return NULL;
    }

    mask_expanded = logger_get_mask_expanded (buffer, mask);
    if (!mask_expanded)
        goto end;

    file_path = logger_get_file_path ();
    if (!file_path)
        goto end;

    /* build string with path + mask */
    length = strlen (file_path) + strlen (dir_separator) +
        strlen (mask_expanded) + 1;
    res = malloc (length);
    if (res)
    {
        snprintf (res, length, "%s%s%s",
                  file_path,
                  (file_path[strlen (file_path) - 1] == dir_separator[0]) ? "" : dir_separator,
                  mask_expanded);
    }

end:
    if (mask_expanded)
        free (mask_expanded);
    if (file_path)
        free (file_path);

    return res;
}

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.