usb: gadget: f_fs: Fix a race condition when processing setup packets.

If the USB driver passes a pointer into the TRB buffer for creq, this
buffer can be overwritten with the status response as soon as the event
is queued. This can make the final check return USB_GADGET_DELAYED_STATUS
when it shouldn't. Instead use the stored wLength.

Fixes: 4d644ab ("usb: gadget: f_fs: Only return delayed status when len is 0")
Cc: stable <[email protected]>
Signed-off-by: Chris Wulff <[email protected]>
Link: https://lore.kernel.org/r/CO1PR17MB5419BD664264A558B2395E28E1112@CO1PR17MB5419.namprd17.prod.outlook.com
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: crwulff

drivers/usb/gadget/function/f_fs.c

@@ -3811,7 +3811,7 @@ static int ffs_func_setup(struct usb_function *f,
 	__ffs_event_add(ffs, FUNCTIONFS_SETUP);
 	spin_unlock_irqrestore(&ffs->ev.waitq.lock, flags);
 
-	return creq->wLength == 0 ? USB_GADGET_DELAYED_STATUS : 0;
+	return ffs->ev.setup.wLength == 0 ? USB_GADGET_DELAYED_STATUS : 0;
 }
 
 static bool ffs_func_req_match(struct usb_function *f,