ProcGrabButton(ClientPtr client)
{
    WindowPtr pWin, confineTo;

    REQUEST(xGrabButtonReq);
    CursorPtr cursor;
    GrabPtr grab;
    DeviceIntPtr ptr, modifierDevice;
    Mask access_mode = DixGrabAccess;
    GrabMask mask;
    GrabParameters param;
    int rc;

    REQUEST_SIZE_MATCH(xGrabButtonReq);
    UpdateCurrentTime();
    if ((stuff->pointerMode != GrabModeSync) &&
        (stuff->pointerMode != GrabModeAsync)) {
        client->errorValue = stuff->pointerMode;
        return BadValue;
    }
    if ((stuff->keyboardMode != GrabModeSync) &&
        (stuff->keyboardMode != GrabModeAsync)) {
        client->errorValue = stuff->keyboardMode;
        return BadValue;
    }
    if ((stuff->modifiers != AnyModifier) &&
        (stuff->modifiers & ~AllModifiersMask)) {
        client->errorValue = stuff->modifiers;
        return BadValue;
    }
    if ((stuff->ownerEvents != xFalse) && (stuff->ownerEvents != xTrue)) {
        client->errorValue = stuff->ownerEvents;
        return BadValue;
    }
    if (stuff->eventMask & ~PointerGrabMask) {
        client->errorValue = stuff->eventMask;
        return BadValue;
    }
    rc = dixLookupWindow(&pWin, stuff->grabWindow, client, DixSetAttrAccess);
    if (rc != Success)
        return rc;
    if (stuff->confineTo == None)
        confineTo = NullWindow;
    else {
        rc = dixLookupWindow(&confineTo, stuff->confineTo, client,
                             DixSetAttrAccess);
        if (rc != Success)
            return rc;
    }
    if (stuff->cursor == None)
        cursor = NullCursor;
    else {
        rc = dixLookupResourceByType((void **) &cursor, stuff->cursor,
                                     RT_CURSOR, client, DixUseAccess);
        if (rc != Success) {
            client->errorValue = stuff->cursor;
            return rc;
        }
        access_mode |= DixForceAccess;
    }

    ptr = PickPointer(client);
    modifierDevice = GetMaster(ptr, MASTER_KEYBOARD);
    if (stuff->pointerMode == GrabModeSync ||
        stuff->keyboardMode == GrabModeSync)
        access_mode |= DixFreezeAccess;
    rc = XaceHook(XACE_DEVICE_ACCESS, client, ptr, access_mode);
    if (rc != Success)
        return rc;

    param = (GrabParameters) {
        .grabtype = CORE,
        .ownerEvents = stuff->ownerEvents,
        .this_device_mode = stuff->keyboardMode,
        .other_devices_mode = stuff->pointerMode,
        .modifiers = stuff->modifiers
    };

    mask.core = stuff->eventMask;

    grab = CreateGrab(client->index, ptr, modifierDevice, pWin,
                      CORE, &mask, &param, ButtonPress,
                      stuff->button, confineTo, cursor);
    if (!grab)
        return BadAlloc;
    return AddPassiveGrabToList(client, grab);
}

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.