linux-kernel - [PATCH 03/20] media: usb: uvc_ctrl.c: add temp variable for list iteration

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Message-Id: <20200807083548.204360-3-dwlsalmeida@gmail.com>
Date:   Fri,  7 Aug 2020 05:35:30 -0300
From:   "Daniel W. S. Almeida" <dwlsalmeida@...il.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     skhan@...uxfoundation.org,
        "Daniel W. S. Almeida" <dwlsalmeida@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 03/20] media: usb: uvc_ctrl.c: add temp variable for list iteration

From: "Daniel W. S. Almeida" <dwlsalmeida@...il.com>

Fixes the following coccinelle report:

drivers/media/usb/uvc/uvc_ctrl.c:1860:5-11:
ERROR: invalid reference to the index variable of the iterator on line 1854

By introducing a temporary variable to iterate the list.

Do not dereference the 'entity' pointer if it is not found in the list.

Found using - Coccinelle (http://coccinelle.lip6.fr)

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@...il.com>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index e399b9fad757..567bdedc2ff2 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -1842,7 +1842,8 @@ static int uvc_ctrl_init_xu_ctrl(struct uvc_device *dev,
 int uvc_xu_ctrl_query(struct uvc_video_chain *chain,
 	struct uvc_xu_control_query *xqry)
 {
-	struct uvc_entity *entity;
+	struct uvc_entity *entity = NULL;
+	struct uvc_entity *cursor = NULL;
 	struct uvc_control *ctrl;
 	unsigned int i, found = 0;
 	u32 reqflags;
@@ -1851,13 +1852,15 @@ int uvc_xu_ctrl_query(struct uvc_video_chain *chain,
 	int ret;
 
 	/* Find the extension unit. */
-	list_for_each_entry(entity, &chain->entities, chain) {
-		if (UVC_ENTITY_TYPE(entity) == UVC_VC_EXTENSION_UNIT &&
-		    entity->id == xqry->unit)
+	list_for_each_entry(cursor, &chain->entities, chain) {
+		if (UVC_ENTITY_TYPE(cursor) == UVC_VC_EXTENSION_UNIT &&
+		    cursor->id == xqry->unit) {
+			entity = cursor;
 			break;
+		    }
 	}
 
-	if (entity->id != xqry->unit) {
+	if (!entity || entity->id != xqry->unit) {
 		uvc_trace(UVC_TRACE_CONTROL, "Extension unit %u not found.\n",
 			xqry->unit);
 		return -ENOENT;
-- 
2.28.0