[PATCH] usb: gadget: mv_u3d: add check for dma mapping error

[Alexey Khoroshilov]

mv_u3d_req_to_trb() does not check for dma mapping errors.

By the way, the patch improves readability of mv_u3d_start_queue()
by rearranging its code with two semantic modifications:
- assignment zero to ep->processing if usb_gadget_map_request() fails;
- propagation of error code from mv_u3d_req_to_trb() instead of 
  hardcoded -ENOMEM.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@xxxxxxxxx>
---
 drivers/usb/gadget/udc/mv_u3d_core.c | 34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/drivers/usb/gadget/udc/mv_u3d_core.c b/drivers/usb/gadget/udc/mv_u3d_core.c
index b9e19a591322..8d726bd767fd 100644
--- a/drivers/usb/gadget/udc/mv_u3d_core.c
+++ b/drivers/usb/gadget/udc/mv_u3d_core.c
@@ -462,6 +462,12 @@ static int mv_u3d_req_to_trb(struct mv_u3d_req *req)
 					req->trb_head->trb_hw,
 					trb_num * sizeof(*trb_hw),
 					DMA_BIDIRECTIONAL);
+		if (dma_mapping_error(u3d->gadget.dev.parent,
+					req->trb_head->trb_dma)) {
+			kfree(req->trb_head->trb_hw);
+			kfree(req->trb_head);
+			return -EFAULT;
+		}
 
 		req->chain = 1;
 	}
@@ -487,30 +493,32 @@ mv_u3d_start_queue(struct mv_u3d_ep *ep)
 	ret = usb_gadget_map_request(&u3d->gadget, &req->req,
 					mv_u3d_ep_dir(ep));
 	if (ret)
-		return ret;
+		goto break_processing;
 
 	req->req.status = -EINPROGRESS;
 	req->req.actual = 0;
 	req->trb_count = 0;
 
-	/* build trbs and push them to device queue */
-	if (!mv_u3d_req_to_trb(req)) {
-		ret = mv_u3d_queue_trb(ep, req);
-		if (ret) {
-			ep->processing = 0;
-			return ret;
-		}
-	} else {
-		ep->processing = 0;
+	/* build trbs */
+	ret = mv_u3d_req_to_trb(req);
+	if (ret) {
 		dev_err(u3d->dev, "%s, mv_u3d_req_to_trb fail\n", __func__);
-		return -ENOMEM;
+		goto break_processing;
 	}
 
+	/* and push them to device queue */
+	ret = mv_u3d_queue_trb(ep, req);
+	if (ret)
+		goto break_processing;
+
 	/* irq handler advances the queue */
-	if (req)
-		list_add_tail(&req->queue, &ep->queue);
+	list_add_tail(&req->queue, &ep->queue);
 
 	return 0;
+
+break_processing:
+	ep->processing = 0;
+	return ret;
 }
 
 static int mv_u3d_ep_enable(struct usb_ep *_ep,
-- 
2.7.4