wifi: mac80211: accept STA changes without link changes

If there's no link ID, then check that there are no changes to
the link, and if so accept them, unless a new link is created.
While at it, reject creating a new link without an address.

This fixes authorizing an MLD (peer) that has no link 0.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/cfg.c

@@ -1610,6 +1610,18 @@ static int sta_link_apply_parameters(struct ieee80211_local *local,
 		rcu_dereference_protected(sta->link[link_id],
 					  lockdep_is_held(&local->sta_mtx));
 
+	/*
+	 * If there are no changes, then accept a link that doesn't exist,
+	 * unless it's a new link.
+	 */
+	if (params->link_id < 0 && !new_link &&
+	    !params->link_mac && !params->txpwr_set &&
+	    !params->supported_rates_len &&
+	    !params->ht_capa && !params->vht_capa &&
+	    !params->he_capa && !params->eht_capa &&
+	    !params->opmode_notif_used)
+		return 0;
+
 	if (!link || !link_sta)
 		return -EINVAL;
 
@@ -1625,6 +1637,8 @@ static int sta_link_apply_parameters(struct ieee80211_local *local,
 					     params->link_mac)) {
 			return -EINVAL;
 		}
+	} else if (new_link) {
+		return -EINVAL;
 	}
 
 	if (params->txpwr_set) {