usbdevfs: Fix broken scatter-gather transfer

The handling of large output bulk transfers is broken; the same user
page is read over and over again. Fixed with this patch.

Cc: stable <[email protected]>
Acked-by: Peter Stuge <[email protected]>
Acked-by: Hans de Goede <[email protected]>
Acked-by: Alan Stern <[email protected]>
Signed-off-by: Henrik Rydberg <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

drivers/usb/core/devio.c

@@ -1348,6 +1348,7 @@ static int proc_do_submiturb(struct dev_state *ps, struct usbdevfs_urb *uurb,
 					ret = -EFAULT;
 					goto error;
 				}
+				uurb->buffer += u;
 			}
 			totlen -= u;
 		}