wifi: mac80211: fix potential key leak

When returning from ieee80211_key_link(), the key needs to
have been freed or successfully installed. This was missed
in a number of error paths, fix it.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/key.c

@@ -802,6 +802,9 @@ static void ieee80211_key_destroy(struct ieee80211_key *key,
 
 void ieee80211_key_free_unused(struct ieee80211_key *key)
 {
+	if (!key)
+		return;
+
 	WARN_ON(key->sdata || key->local);
 	ieee80211_key_free_common(key);
 }
@@ -854,7 +857,7 @@ int ieee80211_key_link(struct ieee80211_key *key,
 	 * can cause warnings to appear.
 	 */
 	bool delay_tailroom = sdata->vif.type == NL80211_IFTYPE_STATION;
-	int ret = -EOPNOTSUPP;
+	int ret;
 
 	mutex_lock(&sdata->local->key_mtx);
 
@@ -868,8 +871,10 @@ int ieee80211_key_link(struct ieee80211_key *key,
 		 * the same cipher. Enforce the assumption for pairwise keys.
 		 */
 		if ((alt_key && alt_key->conf.cipher != key->conf.cipher) ||
-		    (old_key && old_key->conf.cipher != key->conf.cipher))
+		    (old_key && old_key->conf.cipher != key->conf.cipher)) {
+			ret = -EOPNOTSUPP;
 			goto out;
+		}
 	} else if (sta) {
 		struct link_sta_info *link_sta = &sta->deflink;
 		int link_id = key->conf.link_id;
@@ -895,18 +900,19 @@ int ieee80211_key_link(struct ieee80211_key *key,
 
 	/* Non-pairwise keys must also not switch the cipher on rekey */
 	if (!pairwise) {
-		if (old_key && old_key->conf.cipher != key->conf.cipher)
+		if (old_key && old_key->conf.cipher != key->conf.cipher) {
+			ret = -EOPNOTSUPP;
 			goto out;
 		}
+	}
 
 	/*
 	 * Silently accept key re-installation without really installing the
 	 * new version of the key to avoid nonce reuse or replay issues.
 	 */
 	if (ieee80211_key_identical(sdata, old_key, key)) {
-		ieee80211_key_free_unused(key);
 		ret = -EALREADY;
-		goto out;
+		goto unlock;
 	}
 
 	key->local = sdata->local;
@@ -930,7 +936,11 @@ int ieee80211_key_link(struct ieee80211_key *key,
 		ieee80211_key_free(key, delay_tailroom);
 	}
 
+	key = NULL;
+
  out:
+	ieee80211_key_free_unused(key);
+ unlock:
 	mutex_unlock(&sdata->local->key_mtx);
 
 	return ret;