Convert v4l2 event to struct_size

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

drivers/media/v4l2-core/v4l2-event.c

@@ -215,8 +215,7 @@ int v4l2_event_subscribe(struct v4l2_fh *fh,
 	if (elems < 1)
 		elems = 1;
 
-	sev = kvzalloc(sizeof(*sev) + sizeof(struct v4l2_kevent) * elems,
-		       GFP_KERNEL);
+	sev = kvzalloc(struct_size(sev, events, elems), GFP_KERNEL);
 	if (!sev)
 		return -ENOMEM;
 	for (i = 0; i < elems; i++)