usb: gadget: fsl: remove usage of list iterator past the loop body

If the list representing the request queue does not contain the expected
request, the value of the list_for_each_entry() iterator will not point
to a valid structure. To avoid type confusion in such case, the list
iterator scope will be limited to the list_for_each_entry() loop.

In preparation to limiting scope of the list iterator to the list traversal
loop, use a dedicated pointer to point to the found request object [1].

Link: https://lore.kernel.org/all/YhdfEIwI4EdtHdym@kroah.com/
Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
Link: https://lore.kernel.org/r/20220308171818.384491-2-jakobkoschel@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/udc/fsl_qe_udc.c

@@ -1776,7 +1776,8 @@ static int qe_ep_queue(struct usb_ep *_ep, struct usb_request *_req,
 static int qe_ep_dequeue(struct usb_ep *_ep, struct usb_request *_req)
 {
 	struct qe_ep *ep = container_of(_ep, struct qe_ep, ep);
-	struct qe_req *req;
+	struct qe_req *req = NULL;
+	struct qe_req *iter;
 	unsigned long flags;
 
 	if (!_ep || !_req)
@@ -1785,12 +1786,14 @@ static int qe_ep_dequeue(struct usb_ep *_ep, struct usb_request *_req)
 	spin_lock_irqsave(&ep->udc->lock, flags);
 
 	/* make sure it's actually queued on this endpoint */
-	list_for_each_entry(req, &ep->queue, queue) {
-		if (&req->req == _req)
-			break;
+	list_for_each_entry(iter, &ep->queue, queue) {
+		if (&iter->req != _req)
+			continue
+		req = iter;
+		break;
 	}
 
-	if (&req->req != _req) {
+	if (!req) {
 		spin_unlock_irqrestore(&ep->udc->lock, flags);
 		return -EINVAL;
 	}

drivers/usb/gadget/udc/fsl_udc_core.c

@@ -918,7 +918,8 @@ fsl_ep_queue(struct usb_ep *_ep, struct usb_request *_req, gfp_t gfp_flags)
 static int fsl_ep_dequeue(struct usb_ep *_ep, struct usb_request *_req)
 {
 	struct fsl_ep *ep = container_of(_ep, struct fsl_ep, ep);
-	struct fsl_req *req;
+	struct fsl_req *req = NULL;
+	struct fsl_req *iter;
 	unsigned long flags;
 	int ep_num, stopped, ret = 0;
 	u32 epctrl;
@@ -940,11 +941,13 @@ static int fsl_ep_dequeue(struct usb_ep *_ep, struct usb_request *_req)
 	fsl_writel(epctrl, &dr_regs->endptctrl[ep_num]);
 
 	/* make sure it's actually queued on this endpoint */
-	list_for_each_entry(req, &ep->queue, queue) {
-		if (&req->req == _req)
-			break;
+	list_for_each_entry(iter, &ep->queue, queue) {
+		if (&iter->req != _req)
+			continue;
+		req = iter;
+		break;
 	}
-	if (&req->req != _req) {
+	if (!req) {
 		ret = -EINVAL;
 		goto out;
 	}