USB: prevent buggy hubs from crashing the USB stack

If anyone comes across a high-speed hub that (by mistake or by design)
claims to have no Transaction Translators, plugging a full- or
low-speed device into it will cause the USB stack to crash.  This
patch (as1446) prevents the problem by ignoring such devices, since
the kernel has no way to communicate with them.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Perry Neben <neben@vmware.com>
CC: <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/hub.c

@@ -2753,6 +2753,11 @@ hub_port_init (struct usb_hub *hub, struct usb_device *udev, int port1,
 		udev->ttport = hdev->ttport;
 	} else if (udev->speed != USB_SPEED_HIGH
 			&& hdev->speed == USB_SPEED_HIGH) {
+		if (!hub->tt.hub) {
+			dev_err(&udev->dev, "parent hub has no TT\n");
+			retval = -EINVAL;
+			goto fail;
+		}
 		udev->tt = &hub->tt;
 		udev->ttport = port1;
 	}