ActivatePassiveGrab(DeviceIntPtr device, GrabPtr grab, InternalEvent *event,
                    InternalEvent *real_event)
{
    SpritePtr pSprite = device->spriteInfo->sprite;
    GrabInfoPtr grabinfo = &device->deviceGrab;
    xEvent *xE = NULL;
    int count;
    int rc;

    /* The only consumers of corestate are Xi 1.x and core events, which
     * are guaranteed to come from DeviceEvents. */
    if (grab->grabtype == XI || grab->grabtype == CORE) {
        DeviceIntPtr gdev;

        event->device_event.corestate &= 0x1f00;

        if (grab->grabtype == CORE)
            gdev = GetMaster(device, KEYBOARD_OR_FLOAT);
        else
            gdev = grab->modifierDevice;

        if (gdev && gdev->key && gdev->key->xkbInfo)
            event->device_event.corestate |=
                gdev->key->xkbInfo->state.grab_mods & (~0x1f00);
    }

    if (grab->grabtype == CORE) {
        rc = EventToCore(event, &xE, &count);
        if (rc != Success) {
            BUG_WARN_MSG(rc != BadMatch, "[dix] %s: core conversion failed"
                         "(%d, %d).\n", device->name, event->any.type, rc);
            return FALSE;
        }
    }
    else if (grab->grabtype == XI2) {
        rc = EventToXI2(event, &xE);
        if (rc != Success) {
            if (rc != BadMatch)
                BUG_WARN_MSG(rc != BadMatch, "[dix] %s: XI2 conversion failed"
                             "(%d, %d).\n", device->name, event->any.type, rc);
            return FALSE;
        }
        count = 1;
    }
    else {
        rc = EventToXI(event, &xE, &count);
        if (rc != Success) {
            if (rc != BadMatch)
                BUG_WARN_MSG(rc != BadMatch, "[dix] %s: XI conversion failed"
                             "(%d, %d).\n", device->name, event->any.type, rc);
            return FALSE;
        }
    }

    (*grabinfo->ActivateGrab) (device, grab,
                               ClientTimeToServerTime(event->any.time), TRUE);

    if (xE) {
        FixUpEventFromWindow(pSprite, xE, grab->window, None, TRUE);

        /* XXX: XACE? */
        TryClientEvents(rClient(grab), device, xE, count,
                        GetEventFilter(device, xE),
                        GetEventFilter(device, xE), grab);
    }

    if (grabinfo->sync.state == FROZEN_NO_EVENT)
        grabinfo->sync.state = FROZEN_WITH_EVENT;
    *grabinfo->sync.event = real_event->device_event;

    free(xE);
    return TRUE;
}

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.