SetInputFocus(ClientPtr client,
              DeviceIntPtr dev,
              Window focusID, CARD8 revertTo, Time ctime, Bool followOK)
{
    FocusClassPtr focus;
    WindowPtr focusWin;
    int mode, rc;
    TimeStamp time;
    DeviceIntPtr keybd;         /* used for FollowKeyboard or FollowKeyboardWin */

    UpdateCurrentTime();
    if ((revertTo != RevertToParent) &&
        (revertTo != RevertToPointerRoot) &&
        (revertTo != RevertToNone) &&
        ((revertTo != RevertToFollowKeyboard) || !followOK)) {
        client->errorValue = revertTo;
        return BadValue;
    }
    time = ClientTimeToServerTime(ctime);

    keybd = GetMaster(dev, KEYBOARD_OR_FLOAT);

    if ((focusID == None) || (focusID == PointerRoot))
        focusWin = (WindowPtr) (long) focusID;
    else if ((focusID == FollowKeyboard) && followOK) {
        focusWin = keybd->focus->win;
    }
    else {
        rc = dixLookupWindow(&focusWin, focusID, client, DixSetAttrAccess);
        if (rc != Success)
            return rc;
        /* It is a match error to try to set the input focus to an
           unviewable window. */
        if (!focusWin->realized)
            return BadMatch;
    }
    rc = XaceHook(XACE_DEVICE_ACCESS, client, dev, DixSetFocusAccess);
    if (rc != Success)
        return Success;

    focus = dev->focus;
    if ((CompareTimeStamps(time, currentTime) == LATER) ||
        (CompareTimeStamps(time, focus->time) == EARLIER))
        return Success;
    mode = (dev->deviceGrab.grab) ? NotifyWhileGrabbed : NotifyNormal;
    if (focus->win == FollowKeyboardWin) {
        if (!ActivateFocusInGrab(dev, keybd->focus->win, focusWin))
            DoFocusEvents(dev, keybd->focus->win, focusWin, mode);
    }
    else {
        if (!ActivateFocusInGrab(dev, focus->win, focusWin))
            DoFocusEvents(dev, focus->win, focusWin, mode);
    }
    focus->time = time;
    focus->revert = revertTo;
    if (focusID == FollowKeyboard)
        focus->win = FollowKeyboardWin;
    else
        focus->win = focusWin;
    if ((focusWin == NoneWin) || (focusWin == PointerRootWin))
        focus->traceGood = 0;
    else {
        int depth = 0;
        WindowPtr pWin;

        for (pWin = focusWin; pWin; pWin = pWin->parent)
            depth++;
        if (depth > focus->traceSize) {
            focus->traceSize = depth + 1;
            focus->trace = reallocarray(focus->trace, focus->traceSize,
                                        sizeof(WindowPtr));
        }
        focus->traceGood = depth;
        for (pWin = focusWin, depth--; pWin; pWin = pWin->parent, depth--)
            focus->trace[depth] = pWin;
    }
    return Success;
}

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.