mac80211: RCU-ify STA info structure access

This makes access to the STA hash table/list use RCU to protect
against freeing of items. However, it's not a true RCU, the
copy step is missing: whenever somebody changes a STA item it
is simply updated. This is an existing race condition that is
now somewhat understandable.

This patch also fixes the race key freeing vs. STA destruction
by making sure that sta_info_destroy() is always called under
RTNL and frees the key.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 56 insertions, 54 deletions

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 6ac4923..e9ba6fc 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -136,7 +136,6 @@ static int ieee80211_add_key(struct wiphy *wiphy, struct net_device *dev,
 	struct ieee80211_sub_if_data *sdata;
 	struct sta_info *sta = NULL;
 	enum ieee80211_key_alg alg;
-	int ret;
 	struct ieee80211_key *key;
 
 	sdata = IEEE80211_DEV_TO_SUB_IF(dev);
@@ -170,12 +169,7 @@ static int ieee80211_add_key(struct wiphy *wiphy, struct net_device *dev,
 
 	ieee80211_key_link(key, sdata, sta);
 
-	ret = 0;
-
-	if (sta)
-		sta_info_put(sta);
-
-	return ret;
+	return 0;
 }
 
 static int ieee80211_del_key(struct wiphy *wiphy, struct net_device *dev,
@@ -184,7 +178,6 @@ static int ieee80211_del_key(struct wiphy *wiphy, struct net_device *dev,
 	struct ieee80211_sub_if_data *sdata;
 	struct sta_info *sta;
 	int ret;
-	struct ieee80211_key *key;
 
 	sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 
@@ -195,21 +188,18 @@ static int ieee80211_del_key(struct wiphy *wiphy, struct net_device *dev,
 
 		ret = 0;
 		if (sta->key) {
-			key = sta->key;
-			ieee80211_key_free(key);
+			ieee80211_key_free(sta->key);
 			WARN_ON(sta->key);
 		} else
 			ret = -ENOENT;
 
-		sta_info_put(sta);
 		return ret;
 	}
 
 	if (!sdata->keys[key_idx])
 		return -ENOENT;
 
-	key = sdata->keys[key_idx];
-	ieee80211_key_free(key);
+	ieee80211_key_free(sdata->keys[key_idx]);
 	WARN_ON(sdata->keys[key_idx]);
 
 	return 0;
@@ -292,8 +282,6 @@ static int ieee80211_get_key(struct wiphy *wiphy, struct net_device *dev,
 	err = 0;
 
  out:
-	if (sta)
-		sta_info_put(sta);
 	return err;
 }
 
@@ -311,7 +299,7 @@ static int ieee80211_config_default_key(struct wiphy *wiphy,
 
 static void sta_set_sinfo(struct sta_info *sta, struct station_info *sinfo)
 {
-	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
+	struct ieee80211_sub_if_data *sdata = sta->sdata;
 
 	sinfo->filled = STATION_INFO_INACTIVE_TIME |
 			STATION_INFO_RX_BYTES |
@@ -340,16 +328,20 @@ static int ieee80211_dump_station(struct wiphy *wiphy, struct net_device *dev,
 {
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
 	struct sta_info *sta;
+	int ret = -ENOENT;
+
+	rcu_read_lock();
 
 	sta = sta_info_get_by_idx(local, idx, dev);
-	if (!sta)
-		return -ENOENT;
+	if (sta) {
+		ret = 0;
+		memcpy(mac, sta->addr, ETH_ALEN);
+		sta_set_sinfo(sta, sinfo);
+	}
 
-	memcpy(mac, sta->addr, ETH_ALEN);
-	sta_set_sinfo(sta, sinfo);
-	sta_info_put(sta);
+	rcu_read_unlock();
 
-	return 0;
+	return ret;
 }
 
 static int ieee80211_get_station(struct wiphy *wiphy, struct net_device *dev,
@@ -357,16 +349,21 @@ static int ieee80211_get_station(struct wiphy *wiphy, struct net_device *dev,
 {
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
 	struct sta_info *sta;
+	int ret = -ENOENT;
 
-	sta = sta_info_get(local, mac);
-	if (!sta)
-		return -ENOENT;
+	rcu_read_lock();
 
 	/* XXX: verify sta->dev == dev */
-	sta_set_sinfo(sta, sinfo);
-	sta_info_put(sta);
 
-	return 0;
+	sta = sta_info_get(local, mac);
+	if (sta) {
+		ret = 0;
+		sta_set_sinfo(sta, sinfo);
+	}
+
+	rcu_read_unlock();
+
+	return ret;
 }
 
 /*
@@ -559,8 +556,8 @@ static void ieee80211_send_layer2_update(struct sta_info *sta)
 	msg->xid_info[1] = 1;	/* LLC types/classes: Type 1 LLC */
 	msg->xid_info[2] = 0;	/* XID sender's receive window size (RW) */
 
-	skb->dev = sta->dev;
-	skb->protocol = eth_type_trans(skb, sta->dev);
+	skb->dev = sta->sdata->dev;
+	skb->protocol = eth_type_trans(skb, sta->sdata->dev);
 	memset(skb->cb, 0, sizeof(skb->cb));
 	netif_rx(skb);
 }
@@ -572,7 +569,7 @@ static void sta_apply_parameters(struct ieee80211_local *local,
 	u32 rates;
 	int i, j;
 	struct ieee80211_supported_band *sband;
-	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
+	struct ieee80211_sub_if_data *sdata = sta->sdata;
 
 	if (params->station_flags & STATION_FLAG_CHANGED) {
 		sta->flags &= ~WLAN_STA_AUTHORIZED;
@@ -644,14 +641,13 @@ static int ieee80211_add_station(struct wiphy *wiphy, struct net_device *dev,
 		sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 
 	if (ieee80211_vif_is_mesh(&sdata->vif))
-		sta = mesh_plink_add(mac, DEFAULT_RATES, dev);
+		sta = mesh_plink_add(mac, DEFAULT_RATES, sdata);
 	else
-		sta = sta_info_add(local, dev, mac, GFP_KERNEL);
+		sta = sta_info_add(sdata, mac);
 
 	if (IS_ERR(sta))
 		return PTR_ERR(sta);
 
-	sta->dev = sdata->dev;
 	if (sdata->vif.type == IEEE80211_IF_TYPE_VLAN ||
 	    sdata->vif.type == IEEE80211_IF_TYPE_AP)
 		ieee80211_send_layer2_update(sta);
@@ -662,15 +658,14 @@ static int ieee80211_add_station(struct wiphy *wiphy, struct net_device *dev,
 
 	rate_control_rate_init(sta, local);
 
-	sta_info_put(sta);
-
 	return 0;
 }
 
 static int ieee80211_del_station(struct wiphy *wiphy, struct net_device *dev,
 				 u8 *mac)
 {
-	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
+	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+	struct ieee80211_local *local = sdata->local;
 	struct sta_info *sta;
 
 	if (mac) {
@@ -679,10 +674,14 @@ static int ieee80211_del_station(struct wiphy *wiphy, struct net_device *dev,
 		if (!sta)
 			return -ENOENT;
 
-		sta_info_free(sta);
-		sta_info_put(sta);
+		sta_info_unlink(&sta);
+
+		if (sta) {
+			synchronize_rcu();
+			sta_info_destroy(sta);
+		}
 	} else
-		sta_info_flush(local, dev);
+		sta_info_flush(local, sdata);
 
 	return 0;
 }
@@ -701,21 +700,19 @@ static int ieee80211_change_station(struct wiphy *wiphy,
 	if (!sta)
 		return -ENOENT;
 
-	if (params->vlan && params->vlan != sta->dev) {
+	if (params->vlan && params->vlan != sta->sdata->dev) {
 		vlansdata = IEEE80211_DEV_TO_SUB_IF(params->vlan);
 
 		if (vlansdata->vif.type != IEEE80211_IF_TYPE_VLAN ||
 		    vlansdata->vif.type != IEEE80211_IF_TYPE_AP)
 			return -EINVAL;
 
-		sta->dev = params->vlan;
+		sta->sdata = IEEE80211_DEV_TO_SUB_IF(params->vlan);
 		ieee80211_send_layer2_update(sta);
 	}
 
 	sta_apply_parameters(local, sta, params);
 
-	sta_info_put(sta);
-
 	return 0;
 }
 
@@ -735,23 +732,26 @@ static int ieee80211_add_mpath(struct wiphy *wiphy, struct net_device *dev,
 	if (sdata->vif.type != IEEE80211_IF_TYPE_MESH_POINT)
 		return -ENOTSUPP;
 
+	rcu_read_lock();
 	sta = sta_info_get(local, next_hop);
-	if (!sta)
+	if (!sta) {
+		rcu_read_unlock();
 		return -ENOENT;
+	}
 
 	err = mesh_path_add(dst, dev);
-	if (err)
+	if (err) {
+		rcu_read_unlock();
 		return err;
+	}
 
-	rcu_read_lock();
 	mpath = mesh_path_lookup(dst, dev);
 	if (!mpath) {
 		rcu_read_unlock();
-		sta_info_put(sta);
 		return -ENXIO;
 	}
 	mesh_path_fix_nexthop(mpath, sta);
-	sta_info_put(sta);
+
 	rcu_read_unlock();
 	return 0;
 }
@@ -760,7 +760,7 @@ static int ieee80211_del_mpath(struct wiphy *wiphy, struct net_device *dev,
 				 u8 *dst)
 {
 	if (dst)
-		return mesh_path_del(dst, dev);
+		return mesh_path_del(dst, dev, false);
 
 	mesh_path_flush(dev);
 	return 0;
@@ -781,20 +781,22 @@ static int ieee80211_change_mpath(struct wiphy *wiphy,
 	if (sdata->vif.type != IEEE80211_IF_TYPE_MESH_POINT)
 		return -ENOTSUPP;
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, next_hop);
-	if (!sta)
+	if (!sta) {
+		rcu_read_unlock();
 		return -ENOENT;
+	}
 
-	rcu_read_lock();
 	mpath = mesh_path_lookup(dst, dev);
 	if (!mpath) {
 		rcu_read_unlock();
-		sta_info_put(sta);
 		return -ENOENT;
 	}
 
 	mesh_path_fix_nexthop(mpath, sta);
-	sta_info_put(sta);
+
 	rcu_read_unlock();
 	return 0;
 }