usb: dwc3: gadget: Fix desc NULL pointer in dwc3_gadget_ep_queue()

dep->endpoint.desc is checked at the beginning of
dwc3_gadget_ep_queue(), but after that it may be set to NULL
by another thread and then accessed again in dwc3_gadget_ep_queue().
This will lead to kernel oops.

Expand spinlock protection area to aviod race condition.
Signed-off-by: Zhuang Jin Can <jin.can.zhuang@intel.com>
Signed-off-by: Jiebing Li <jiebing.li@intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/gadget.c

@@ -1225,16 +1225,17 @@ static int dwc3_gadget_ep_queue(struct usb_ep *ep, struct usb_request *request,
 
 	int				ret;
 
+	spin_lock_irqsave(&dwc->lock, flags);
 	if (!dep->endpoint.desc) {
 		dev_dbg(dwc->dev, "trying to queue request %p to disabled %s\n",
 				request, ep->name);
+		spin_unlock_irqrestore(&dwc->lock, flags);
 		return -ESHUTDOWN;
 	}
 
 	dev_vdbg(dwc->dev, "queing request %p to %s length %d\n",
 			request, ep->name, request->length);
 
-	spin_lock_irqsave(&dwc->lock, flags);
 	ret = __dwc3_gadget_ep_queue(dep, req);
 	spin_unlock_irqrestore(&dwc->lock, flags);