USB: Fix SS endpoint companion descriptor parsing.

commit 6682bb39 upstream.

When there's a descriptor after the SuperSpeed endpoint companion
descriptor, the previous code would have skipped over twice the length it
was supposed to.  This code fixes crashes seen with UASP devices (which
have a UASP descriptor after the SS endpoint companion descriptor).
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/config.c

@@ -105,7 +105,7 @@ static int usb_parse_ss_endpoint_companion(struct device *ddev, int cfgno,
 	ep->ss_ep_comp->extralen = i;
 	buffer += i;
 	size -= i;
-	retval = buffer - buffer_start + i;
+	retval = buffer - buffer_start;
 	if (num_skipped > 0)
 		dev_dbg(ddev, "skipped %d descriptor%s after %s\n",
 				num_skipped, plural(num_skipped),