mac80211: Fix key freeing to handle unlinked keys

Key locking simplification removed key->sdata != NULL verification from
ieee80211_key_free(). While that is fine for most use cases, there is one
path where this function can be called with an unlinked key (i.e.,
key->sdata == NULL && key->local == NULL). This results in a NULL pointer
dereference with the current implementation. This is known to happen at
least with FT protocol when wpa_supplicant tries to configure the key
before association.

Avoid the issue by passing in the local pointer to
ieee80211_key_free(). In addition, do not clear the key from hw_accel
or debugfs if it has not yet been added. At least the hw_accel one could
trigger another NULL pointer dereference.
Signed-off-by: Jouni Malinen <j@w1.fi>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/cfg.c

@@ -158,7 +158,7 @@ static int ieee80211_add_key(struct wiphy *wiphy, struct net_device *dev,
 	if (mac_addr) {
 		sta = sta_info_get_bss(sdata, mac_addr);
 		if (!sta) {
-			ieee80211_key_free(key);
+			ieee80211_key_free(sdata->local, key);
 			err = -ENOENT;
 			goto out_unlock;
 		}
@@ -192,7 +192,7 @@ static int ieee80211_del_key(struct wiphy *wiphy, struct net_device *dev,
 			goto out_unlock;
 
 		if (sta->key) {
-			ieee80211_key_free(sta->key);
+			ieee80211_key_free(sdata->local, sta->key);
 			WARN_ON(sta->key);
 			ret = 0;
 		}
@@ -205,7 +205,7 @@ static int ieee80211_del_key(struct wiphy *wiphy, struct net_device *dev,
 		goto out_unlock;
 	}
 
-	ieee80211_key_free(sdata->keys[key_idx]);
+	ieee80211_key_free(sdata->local, sdata->keys[key_idx]);
 	WARN_ON(sdata->keys[key_idx]);
 
 	ret = 0;

net/mac80211/key.c

@@ -323,12 +323,14 @@ static void __ieee80211_key_destroy(struct ieee80211_key *key)
 	if (!key)
 		return;
 
+	if (key->local)
 		ieee80211_key_disable_hw_accel(key);
 
 	if (key->conf.alg == ALG_CCMP)
 		ieee80211_aes_key_free(key->u.ccmp.tfm);
 	if (key->conf.alg == ALG_AES_CMAC)
 		ieee80211_aes_cmac_key_free(key->u.aes_cmac.tfm);
+	if (key->local)
 		ieee80211_debugfs_key_remove(key);
 
 	kfree(key);
@@ -410,15 +412,12 @@ static void __ieee80211_key_free(struct ieee80211_key *key)
 	__ieee80211_key_destroy(key);
 }
 
-void ieee80211_key_free(struct ieee80211_key *key)
+void ieee80211_key_free(struct ieee80211_local *local,
+			struct ieee80211_key *key)
 {
-	struct ieee80211_local *local;
-
 	if (!key)
 		return;
 
-	local = key->sdata->local;
-
 	mutex_lock(&local->key_mtx);
 	__ieee80211_key_free(key);
 	mutex_unlock(&local->key_mtx);

net/mac80211/key.h

@@ -135,7 +135,8 @@ struct ieee80211_key *ieee80211_key_alloc(enum ieee80211_key_alg alg,
 void ieee80211_key_link(struct ieee80211_key *key,
 			struct ieee80211_sub_if_data *sdata,
 			struct sta_info *sta);
-void ieee80211_key_free(struct ieee80211_key *key);
+void ieee80211_key_free(struct ieee80211_local *local,
+			struct ieee80211_key *key);
 void ieee80211_set_default_key(struct ieee80211_sub_if_data *sdata, int idx);
 void ieee80211_set_default_mgmt_key(struct ieee80211_sub_if_data *sdata,
 				    int idx);

net/mac80211/sta_info.c

@@ -647,7 +647,7 @@ static int __must_check __sta_info_destroy(struct sta_info *sta)
 		return ret;
 
 	if (sta->key) {
-		ieee80211_key_free(sta->key);
+		ieee80211_key_free(local, sta->key);
 		WARN_ON(sta->key);
 	}