usb-ehci: sanity-check iso xfers

This patch adds a sanity check to itd processing to make sure the
endpoint addressed by the guest is actually an iso endpoint.  Also
verify that usb drivers don't return USB_RET_ASYNC which is illegal for
iso xfers.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/usb-ehci.c

@@ -1459,12 +1459,16 @@ static int ehci_process_itd(EHCIState *ehci,
 
             dev = ehci_find_device(ehci, devaddr);
             ep = usb_ep_get(dev, pid, endp);
+            if (ep->type == USB_ENDPOINT_XFER_ISOC) {
                 usb_packet_setup(&ehci->ipacket, pid, ep);
                 usb_packet_map(&ehci->ipacket, &ehci->isgl);
-
                 ret = usb_handle_packet(dev, &ehci->ipacket);
-
+                assert(ret != USB_RET_ASYNC);
                 usb_packet_unmap(&ehci->ipacket);
+            } else {
+                DPRINTF("ISOCH: attempt to addess non-iso endpoint\n");
+                ret = USB_RET_NAK;
+            }
             qemu_sglist_destroy(&ehci->isgl);
 
 #if 0