nl80211: Check for the required netlink attribute presence

nl80211_nan_add_func() does not check if the required attribute
NL80211_NAN_FUNC_FOLLOW_UP_DEST is present when processing
NL80211_CMD_ADD_NAN_FUNCTION request. This request can be issued
by users with CAP_NET_ADMIN privilege and may result in NULL dereference
and a system crash. Add a check for the required attribute presence.

Signed-off-by: Hao Chen <flank3rsky@gmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/nl80211.c

@@ -11361,7 +11361,8 @@ static int nl80211_nan_add_func(struct sk_buff *skb,
 		break;
 	case NL80211_NAN_FUNC_FOLLOW_UP:
 		if (!tb[NL80211_NAN_FUNC_FOLLOW_UP_ID] ||
-		    !tb[NL80211_NAN_FUNC_FOLLOW_UP_REQ_ID]) {
+		    !tb[NL80211_NAN_FUNC_FOLLOW_UP_REQ_ID] ||
+		    !tb[NL80211_NAN_FUNC_FOLLOW_UP_DEST]) {
 			err = -EINVAL;
 			goto out;
 		}