USB: usb_parse_endpoint: ignore reserved bits

Reading bEndpointAddress the spec tells is that:
  b7   is direction, which must be ignored
  b6:4 are reserved which are to be set to zero
  b3:0 are the endpoint address

In order to be backwards compatible with possible future versions of USB
we have to be ready with devices using those bits. That means that we
also have to ignore them like we do with the direction bit.

In consequence the only illegal address you can encoding in four bits is
endpoint zero, for which no descriptor must exist. Hence the check for
exceeding the upper limit on endpoint addresses is removed.

Signed-off-by: Oliver Neukum <[email protected]>
Reviewed-by: Alan Stern <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: oneukum

drivers/usb/core/config.c

@@ -279,11 +279,11 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno,
 		goto skip_to_next_endpoint_or_interface_descriptor;
 	}
 
-	i = d->bEndpointAddress & ~USB_ENDPOINT_DIR_MASK;
-	if (i >= 16 || i == 0) {
+	i = d->bEndpointAddress & USB_ENDPOINT_NUMBER_MASK;
+	if (i == 0) {
 		dev_notice(ddev, "config %d interface %d altsetting %d has an "
-		    "invalid endpoint with address 0x%X, skipping\n",
-		    cfgno, inum, asnum, d->bEndpointAddress);
+		    "invalid descriptor for endpoint zero, skipping\n",
+		    cfgno, inum, asnum);
 		goto skip_to_next_endpoint_or_interface_descriptor;
 	}