nl80211: use for_each_element() in validate_ie_attr()

This makes for much simpler code, simply walk through all
the elements and check that the last one found ends with
the end of the data. This works because if any element is
malformed the walk is aborted, we end up with a mismatch.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/nl80211.c

@@ -203,29 +203,17 @@ cfg80211_get_dev_from_info(struct net *netns, struct genl_info *info)
 static int validate_ie_attr(const struct nlattr *attr,
 			    struct netlink_ext_ack *extack)
 {
-	const u8 *pos;
-	int len;
+	const u8 *data = nla_data(attr);
+	unsigned int len = nla_len(attr);
+	struct element *elem;
 
-	pos = nla_data(attr);
-	len = nla_len(attr);
-
-	while (len) {
-		u8 elemlen;
-
-		if (len < 2)
-			goto error;
-		len -= 2;
-
-		elemlen = pos[1];
-		if (elemlen > len)
-			goto error;
-
-		len -= elemlen;
-		pos += 2 + elemlen;
+	for_each_element(elem, data, len) {
+		/* nothing */
 	}
 
-	return 0;
-error:
+	if (for_each_element_completed(elem, data, len))
+		return 0;
+
 	NL_SET_ERR_MSG_ATTR(extack, attr, "malformed information elements");
 	return -EINVAL;
 }