USB: hub: fix SS max number of ports

Add define for the maximum number of ports on a SuperSpeed hub as per
USB 3.1 spec Table 10-5, and use it when verifying the retrieved hub
descriptor.

This specifically avoids benign attempts to update the DeviceRemovable
mask for non-existing ports (should we get that far).

Fixes: dbe79bbe9dcb ("USB 3.0 Hub Changes")
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/hub.c

@@ -1336,7 +1336,13 @@ static int hub_configure(struct usb_hub *hub,
 	if (ret < 0) {
 		message = "can't read hub descriptor";
 		goto fail;
-	} else if (hub->descriptor->bNbrPorts > USB_MAXCHILDREN) {
+	}
+
+	maxchild = USB_MAXCHILDREN;
+	if (hub_is_superspeed(hdev))
+		maxchild = min_t(unsigned, maxchild, USB_SS_MAXPORTS);
+
+	if (hub->descriptor->bNbrPorts > maxchild) {
 		message = "hub has too many ports!";
 		ret = -ENODEV;
 		goto fail;

include/uapi/linux/usb/ch11.h

@@ -22,6 +22,9 @@
  */
 #define USB_MAXCHILDREN		31
 
+/* See USB 3.1 spec Table 10-5 */
+#define USB_SS_MAXPORTS		15
+
 /*
  * Hub request types
  */