[PATCH 4/6] usb: gadget: mv_udc: check endpoint before queue dtd

[Neil Zhang <zhangwm@marvell.com>]

There is a corner case that endpoint is disabled by system shutdown
between check ep->desc and hold spin lock in mv_ep_queue. In this
case ep->ep.desc will be NULL and occur kernel panic when access
it in build_dtd.

Signed-off-by: Neil Zhang <zhangwm@marvell.com>
---
 drivers/usb/gadget/mv_udc_core.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/usb/gadget/mv_udc_core.c b/drivers/usb/gadget/mv_udc_core.c
index d5a9bdf..a620cff 100644
--- a/drivers/usb/gadget/mv_udc_core.c
+++ b/drivers/usb/gadget/mv_udc_core.c
@@ -734,6 +734,14 @@ mv_ep_queue(struct usb_ep *_ep, struct usb_request *_req, gfp_t gfp_flags)
 
 	spin_lock_irqsave(&udc->lock, flags);
 
+	if (!ep->ep.desc) {
+		spin_unlock_irqrestore(&udc->lock, flags);
+		dev_info(&udc->dev->dev,
+			"%s is already disabled!\n", ep->name);
+		retval = -EINVAL;
+		goto err_unmap_dma;
+	}
+
 	/* build dtds and push them to device queue */
 	if (!req_to_dtd(req)) {
 		retval = queue_dtd(ep, req);
-- 
1.7.9.5