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>

drivers/net/wireless/iwlwifi/iwl-3945-rs.c

@@ -471,10 +471,11 @@ static void rs_tx_status(void *priv_rate,
 		return;
 	}
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, hdr->addr1);
 	if (!sta || !sta->rate_ctrl_priv) {
-		if (sta)
-			sta_info_put(sta);
+		rcu_read_unlock();
 		IWL_DEBUG_RATE("leave: No STA priv data to update!\n");
 		return;
 	}
@@ -547,7 +548,7 @@ static void rs_tx_status(void *priv_rate,
 
 	spin_unlock_irqrestore(&rs_sta->lock, flags);
 
-	sta_info_put(sta);
+	rcu_read_unlock();
 
 	IWL_DEBUG_RATE("leave\n");
 
@@ -658,6 +659,8 @@ static void rs_get_rate(void *priv_rate, struct net_device *dev,
 
 	IWL_DEBUG_RATE("enter\n");
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, hdr->addr1);
 
 	/* Send management frames and broadcast/multicast data using lowest
@@ -668,8 +671,7 @@ static void rs_get_rate(void *priv_rate, struct net_device *dev,
 	    !sta || !sta->rate_ctrl_priv) {
 		IWL_DEBUG_RATE("leave: No STA priv data to update!\n");
 		sel->rate = rate_lowest(local, band, sta);
-		if (sta)
-			sta_info_put(sta);
+		rcu_read_unlock();
 		return;
 	}
 
@@ -811,7 +813,7 @@ static void rs_get_rate(void *priv_rate, struct net_device *dev,
 	else
 		sta->txrate_idx = sta->last_txrate_idx;
 
-	sta_info_put(sta);
+	rcu_read_unlock();
 
 	IWL_DEBUG_RATE("leave: %d\n", index);
 
@@ -843,13 +845,15 @@ int iwl3945_fill_rs_info(struct ieee80211_hw *hw, char *buf, u8 sta_id)
 	unsigned long now = jiffies;
 	u32 max_time = 0;
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, priv->stations[sta_id].sta.sta.addr);
 	if (!sta || !sta->rate_ctrl_priv) {
-		if (sta) {
-			sta_info_put(sta);
+		if (sta)
 			IWL_DEBUG_RATE("leave - no private rate data!\n");
-		} else
+		else
 			IWL_DEBUG_RATE("leave - no station!\n");
+		rcu_read_unlock();
 		return sprintf(buf, "station %d not found\n", sta_id);
 	}
 
@@ -890,7 +894,7 @@ int iwl3945_fill_rs_info(struct ieee80211_hw *hw, char *buf, u8 sta_id)
 		i = j;
 	}
 	spin_unlock_irqrestore(&rs_sta->lock, flags);
-	sta_info_put(sta);
+	rcu_read_unlock();
 
 	/* Display the average rate of all samples taken.
 	 *
@@ -927,11 +931,12 @@ void iwl3945_rate_scale_init(struct ieee80211_hw *hw, s32 sta_id)
 		return;
 	}
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, priv->stations[sta_id].sta.sta.addr);
 	if (!sta || !sta->rate_ctrl_priv) {
-		if (sta)
-			sta_info_put(sta);
 		IWL_DEBUG_RATE("leave - no private rate data!\n");
+		rcu_read_unlock();
 		return;
 	}
 
@@ -958,7 +963,7 @@ void iwl3945_rate_scale_init(struct ieee80211_hw *hw, s32 sta_id)
 		break;
 	}
 
-	sta_info_put(sta);
+	rcu_read_unlock();
 	spin_unlock_irqrestore(&rs_sta->lock, flags);
 
 	rssi = priv->last_rx_rssi;

drivers/net/wireless/iwlwifi/iwl-4965-rs.c

@@ -847,12 +847,12 @@ static void rs_tx_status(void *priv_rate, struct net_device *dev,
 	if (retries > 15)
 		retries = 15;
 
+	rcu_read_lock();
 
 	sta = sta_info_get(local, hdr->addr1);
 
 	if (!sta || !sta->rate_ctrl_priv) {
-		if (sta)
-			sta_info_put(sta);
+		rcu_read_unlock();
 		return;
 	}
 
@@ -891,7 +891,7 @@ static void rs_tx_status(void *priv_rate, struct net_device *dev,
 	if ((rs_index < 0) || (rs_index >= IWL_RATE_COUNT)) {
 		IWL_DEBUG_RATE("bad rate index at: %d rate 0x%X\n",
 			     rs_index, tx_mcs.rate_n_flags);
-		sta_info_put(sta);
+		rcu_read_unlock();
 		return;
 	}
 
@@ -909,7 +909,7 @@ static void rs_tx_status(void *priv_rate, struct net_device *dev,
 		IWL_DEBUG_RATE("initial rate does not match 0x%x 0x%x\n",
 				tx_mcs.rate_n_flags,
 				le32_to_cpu(table->rs_table[0].rate_n_flags));
-		sta_info_put(sta);
+		rcu_read_unlock();
 		return;
 	}
 
@@ -1025,7 +1025,7 @@ static void rs_tx_status(void *priv_rate, struct net_device *dev,
 
 	/* See if there's a better rate or modulation mode to try. */
 	rs_rate_scale_perform(priv, dev, hdr, sta);
-	sta_info_put(sta);
+	rcu_read_unlock();
 	return;
 }
 
@@ -2219,6 +2219,8 @@ static void rs_get_rate(void *priv_rate, struct net_device *dev,
 
 	IWL_DEBUG_RATE_LIMIT("rate scale calculate new rate for skb\n");
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, hdr->addr1);
 
 	/* Send management frames and broadcast/multicast data using lowest
@@ -2227,8 +2229,7 @@ static void rs_get_rate(void *priv_rate, struct net_device *dev,
 	if (!ieee80211_is_data(fc) || is_multicast_ether_addr(hdr->addr1) ||
 	    !sta || !sta->rate_ctrl_priv) {
 		sel->rate = rate_lowest(local, sband, sta);
-		if (sta)
-			sta_info_put(sta);
+		rcu_read_unlock();
 		return;
 	}
 
@@ -2261,7 +2262,7 @@ static void rs_get_rate(void *priv_rate, struct net_device *dev,
 		sel->rate = rate_lowest(local, sband, sta);
 		return;
 	}
-	sta_info_put(sta);
+	rcu_read_unlock();
 
 	sel->rate = &priv->ieee_rates[i];
 }
@@ -2735,13 +2736,15 @@ int iwl4965_fill_rs_info(struct ieee80211_hw *hw, char *buf, u8 sta_id)
 	u32 max_time = 0;
 	u8 lq_type, antenna;
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, priv->stations[sta_id].sta.sta.addr);
 	if (!sta || !sta->rate_ctrl_priv) {
-		if (sta) {
-			sta_info_put(sta);
+		if (sta)
 			IWL_DEBUG_RATE("leave - no private rate data!\n");
-		} else
+		else
 			IWL_DEBUG_RATE("leave - no station!\n");
+		rcu_read_unlock();
 		return sprintf(buf, "station %d not found\n", sta_id);
 	}
 
@@ -2808,7 +2811,7 @@ int iwl4965_fill_rs_info(struct ieee80211_hw *hw, char *buf, u8 sta_id)
 			 "active_search %d rate index %d\n", lq_type, antenna,
 			 lq_sta->search_better_tbl, sta->last_txrate_idx);
 
-	sta_info_put(sta);
+	rcu_read_unlock();
 	return cnt;
 }
 

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;
 }

net/mac80211/debugfs_sta.c

@@ -51,7 +51,7 @@ static const struct file_operations sta_ ##name## _ops = {		\
 		STA_OPS(name)
 
 STA_FILE(aid, aid, D);
-STA_FILE(dev, dev->name, S);
+STA_FILE(dev, sdata->dev->name, S);
 STA_FILE(rx_packets, rx_packets, LU);
 STA_FILE(tx_packets, tx_packets, LU);
 STA_FILE(rx_bytes, rx_bytes, LU);
@@ -200,7 +200,7 @@ static ssize_t sta_agg_status_write(struct file *file,
 		const char __user *user_buf, size_t count, loff_t *ppos)
 {
 	struct sta_info *sta = file->private_data;
-	struct net_device *dev = sta->dev;
+	struct net_device *dev = sta->sdata->dev;
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
 	struct ieee80211_hw *hw = &local->hw;
 	u8 *da = sta->addr;

net/mac80211/debugfs_sta.h

 #ifndef __MAC80211_DEBUGFS_STA_H
 #define __MAC80211_DEBUGFS_STA_H
 
+#include "sta_info.h"
+
 #ifdef CONFIG_MAC80211_DEBUGFS
 void ieee80211_sta_debugfs_add(struct sta_info *sta);
 void ieee80211_sta_debugfs_remove(struct sta_info *sta);

net/mac80211/ieee80211.c

@@ -375,15 +375,19 @@ static int ieee80211_stop(struct net_device *dev)
 
 	sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 
-	list_for_each_entry(sta, &local->sta_list, list) {
-		if (sta->dev == dev)
+	rcu_read_lock();
+
+	list_for_each_entry_rcu(sta, &local->sta_list, list) {
+		if (sta->sdata == sdata)
 			for (i = 0; i <  STA_TID_NUM; i++)
-				ieee80211_sta_stop_rx_ba_session(sta->dev,
+				ieee80211_sta_stop_rx_ba_session(sdata->dev,
 						sta->addr, i,
 						WLAN_BACK_RECIPIENT,
 						WLAN_REASON_QSTA_LEAVE_QBSS);
 	}
 
+	rcu_read_unlock();
+
 	netif_stop_queue(dev);
 
 	/*
@@ -449,7 +453,7 @@ static int ieee80211_stop(struct net_device *dev)
 		netif_tx_unlock_bh(local->mdev);
 		break;
 	case IEEE80211_IF_TYPE_MESH_POINT:
-		sta_info_flush(local, dev);
+		sta_info_flush(local, sdata);
 		/* fall through */
 	case IEEE80211_IF_TYPE_STA:
 	case IEEE80211_IF_TYPE_IBSS:
@@ -522,9 +526,12 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 				print_mac(mac, ra), tid);
 #endif /* CONFIG_MAC80211_HT_DEBUG */
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, ra);
 	if (!sta) {
 		printk(KERN_DEBUG "Could not find the station\n");
+		rcu_read_unlock();
 		return -ENOENT;
 	}
 
@@ -564,7 +571,7 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 		spin_unlock_bh(&local->mdev->queue_lock);
 		goto start_ba_exit;
 	}
-	sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
+	sdata = sta->sdata;
 
 	/* Ok, the Addba frame hasn't been sent yet, but if the driver calls the
 	 * call back right away, it must see that the flow has begun */
@@ -601,7 +608,7 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 			sta->ampdu_mlme.dialog_token_allocator;
 	sta->ampdu_mlme.tid_tx[tid].ssn = start_seq_num;
 
-	ieee80211_send_addba_request(sta->dev, ra, tid,
+	ieee80211_send_addba_request(sta->sdata->dev, ra, tid,
 			 sta->ampdu_mlme.tid_tx[tid].dialog_token,
 			 sta->ampdu_mlme.tid_tx[tid].ssn,
 			 0x40, 5000);
@@ -614,7 +621,7 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 
 start_ba_exit:
 	spin_unlock_bh(&sta->ampdu_mlme.ampdu_tx);
-	sta_info_put(sta);
+	rcu_read_unlock();
 	return ret;
 }
 EXPORT_SYMBOL(ieee80211_start_tx_ba_session);
@@ -637,9 +644,12 @@ int ieee80211_stop_tx_ba_session(struct ieee80211_hw *hw,
 				print_mac(mac, ra), tid);
 #endif /* CONFIG_MAC80211_HT_DEBUG */
 
+	rcu_read_lock();
 	sta = sta_info_get(local, ra);
-	if (!sta)
+	if (!sta) {
+		rcu_read_unlock();
 		return -ENOENT;
+	}
 
 	/* check if the TID is in aggregation */
 	state = &sta->ampdu_mlme.tid_tx[tid].state;
@@ -673,7 +683,7 @@ int ieee80211_stop_tx_ba_session(struct ieee80211_hw *hw,
 
 stop_BA_exit:
 	spin_unlock_bh(&sta->ampdu_mlme.ampdu_tx);
-	sta_info_put(sta);
+	rcu_read_unlock();
 	return ret;
 }
 EXPORT_SYMBOL(ieee80211_stop_tx_ba_session);
@@ -691,8 +701,10 @@ void ieee80211_start_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 		return;
 	}
 
+	rcu_read_lock();
 	sta = sta_info_get(local, ra);
 	if (!sta) {
+		rcu_read_unlock();
 		printk(KERN_DEBUG "Could not find station: %s\n",
 				print_mac(mac, ra));
 		return;
@@ -705,7 +717,7 @@ void ieee80211_start_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 		printk(KERN_DEBUG "addBA was not requested yet, state is %d\n",
 				*state);
 		spin_unlock_bh(&sta->ampdu_mlme.ampdu_tx);
-		sta_info_put(sta);
+		rcu_read_unlock();
 		return;
 	}
 
@@ -718,7 +730,7 @@ void ieee80211_start_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u16 tid)
 		ieee80211_wake_queue(hw, sta->tid_to_tx_q[tid]);
 	}
 	spin_unlock_bh(&sta->ampdu_mlme.ampdu_tx);
-	sta_info_put(sta);
+	rcu_read_unlock();
 }
 EXPORT_SYMBOL(ieee80211_start_tx_ba_cb);
 
@@ -739,10 +751,12 @@ void ieee80211_stop_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u8 tid)
 	printk(KERN_DEBUG "Stop a BA session requested on DA %s tid %d\n",
 				print_mac(mac, ra), tid);
 
+	rcu_read_lock();
 	sta = sta_info_get(local, ra);
 	if (!sta) {
 		printk(KERN_DEBUG "Could not find station: %s\n",
 				print_mac(mac, ra));
+		rcu_read_unlock();
 		return;
 	}
 	state = &sta->ampdu_mlme.tid_tx[tid].state;
@@ -750,13 +764,13 @@ void ieee80211_stop_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u8 tid)
 	spin_lock_bh(&sta->ampdu_mlme.ampdu_tx);
 	if ((*state & HT_AGG_STATE_REQ_STOP_BA_MSK) == 0) {
 		printk(KERN_DEBUG "unexpected callback to A-MPDU stop\n");
-		sta_info_put(sta);
 		spin_unlock_bh(&sta->ampdu_mlme.ampdu_tx);
+		rcu_read_unlock();
 		return;
 	}
 
 	if (*state & HT_AGG_STATE_INITIATOR_MSK)
-		ieee80211_send_delba(sta->dev, ra, tid,
+		ieee80211_send_delba(sta->sdata->dev, ra, tid,
 			WLAN_BACK_INITIATOR, WLAN_REASON_QSTA_NOT_USE);
 
 	agg_queue = sta->tid_to_tx_q[tid];
@@ -777,7 +791,7 @@ void ieee80211_stop_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u8 tid)
 	sta->ampdu_mlme.tid_tx[tid].addba_req_num = 0;
 	spin_unlock_bh(&sta->ampdu_mlme.ampdu_tx);
 
-	sta_info_put(sta);
+	rcu_read_unlock();
 }
 EXPORT_SYMBOL(ieee80211_stop_tx_ba_cb);
 
@@ -887,32 +901,41 @@ int ieee80211_if_update_wds(struct net_device *dev, u8 *remote_addr)
 	struct sta_info *sta;
 	DECLARE_MAC_BUF(mac);
 
+	might_sleep();
+
 	if (compare_ether_addr(remote_addr, sdata->u.wds.remote_addr) == 0)
 		return 0;
 
+	rcu_read_lock();
+
 	/* Create STA entry for the new peer */
-	sta = sta_info_add(local, dev, remote_addr, GFP_KERNEL);
-	if (IS_ERR(sta))
+	sta = sta_info_add(sdata, remote_addr);
+	if (IS_ERR(sta)) {
+		rcu_read_unlock();
 		return PTR_ERR(sta);
+	}
 
 	sta->flags |= WLAN_STA_AUTHORIZED;
 
-	sta_info_put(sta);
-
 	/* Remove STA entry for the old peer */
 	sta = sta_info_get(local, sdata->u.wds.remote_addr);
-	if (sta) {
-		sta_info_free(sta);
-		sta_info_put(sta);
-	} else {
+	if (sta)
+		sta_info_unlink(&sta);
+	else
 		printk(KERN_DEBUG "%s: could not find STA entry for WDS link "
 		       "peer %s\n",
 		       dev->name, print_mac(mac, sdata->u.wds.remote_addr));
-	}
 
 	/* Update WDS link data */
 	memcpy(&sdata->u.wds.remote_addr, remote_addr, ETH_ALEN);
 
+	rcu_read_unlock();
+
+	if (sta) {
+		synchronize_rcu();
+		sta_info_destroy(sta);
+	}
+
 	return 0;
 }
 
@@ -1330,6 +1353,8 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb,
 		return;
 	}
 
+	rcu_read_lock();
+
 	if (status->excessive_retries) {
 		struct sta_info *sta;
 		sta = sta_info_get(local, hdr->addr1);
@@ -1343,10 +1368,9 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb,
 				status->flags |= IEEE80211_TX_STATUS_TX_FILTERED;
 				ieee80211_handle_filtered_frame(local, sta,
 								skb, status);
-				sta_info_put(sta);
+				rcu_read_unlock();
 				return;
 			}
-			sta_info_put(sta);
 		}
 	}
 
@@ -1356,12 +1380,14 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb,
 		if (sta) {
 			ieee80211_handle_filtered_frame(local, sta, skb,
 							status);
-			sta_info_put(sta);
+			rcu_read_unlock();
 			return;
 		}
 	} else
 		rate_control_tx_status(local->mdev, skb, status);
 
+	rcu_read_unlock();
+
 	ieee80211_led_tx(local, 0);
 
 	/* SNMP counters

net/mac80211/ieee80211_i.h

@@ -574,6 +574,7 @@ struct ieee80211_local {
 	unsigned int filter_flags; /* FIF_* */
 	struct iw_statistics wstats;
 	u8 wstats_flags;
+	bool tim_in_locked_section; /* see ieee80211_beacon_get() */
 	int tx_headroom; /* required headroom for hardware/radiotap */
 
 	enum {
@@ -591,9 +592,15 @@ struct ieee80211_local {
 	struct sk_buff_head skb_queue;
 	struct sk_buff_head skb_queue_unreliable;
 
-	/* Station data structures */
-	rwlock_t sta_lock; /* protects STA data structures */
-	int num_sta; /* number of stations in sta_list */
+	/* Station data */
+	/*
+	 * The lock only protects the list, hash, timer and counter
+	 * against manipulation, reads are done in RCU. Additionally,
+	 * the lock protects each BSS's TIM bitmap and a few items
+	 * in a STA info structure.
+	 */
+	spinlock_t sta_lock;
+	unsigned long num_sta;
 	struct list_head sta_list;
 	struct sta_info *sta_hash[STA_HASH_SIZE];
 	struct timer_list sta_cleanup;

net/mac80211/ieee80211_iface.c

@@ -240,16 +240,21 @@ void ieee80211_if_reinit(struct net_device *dev)
 		break;
 	}
 	case IEEE80211_IF_TYPE_WDS:
+		rcu_read_lock();
 		sta = sta_info_get(local, sdata->u.wds.remote_addr);
 		if (sta) {
-			sta_info_free(sta);
-			sta_info_put(sta);
+			sta_info_unlink(&sta);
 		} else {
 #ifdef CONFIG_MAC80211_VERBOSE_DEBUG
 			printk(KERN_DEBUG "%s: Someone had deleted my STA "
 			       "entry for the WDS link\n", dev->name);
 #endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
 		}
+		rcu_read_unlock();
+		if (sta) {
+			synchronize_rcu();
+			sta_info_destroy(sta);
+		}
 		break;
 	case IEEE80211_IF_TYPE_MESH_POINT:
 	case IEEE80211_IF_TYPE_STA:
@@ -275,7 +280,7 @@ void ieee80211_if_reinit(struct net_device *dev)
 	}
 
 	/* remove all STAs that are bound to this virtual interface */
-	sta_info_flush(local, dev);
+	sta_info_flush(local, sdata);
 
 	memset(&sdata->u, 0, sizeof(sdata->u));
 	ieee80211_if_sdata_init(sdata);

net/mac80211/ieee80211_ioctl.c

@@ -33,8 +33,7 @@ static int ieee80211_set_encryption(struct net_device *dev, u8 *sta_addr,
 				    size_t key_len)
 {
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
-	int ret;
-	struct sta_info *sta = NULL;
+	struct sta_info *sta;
 	struct ieee80211_key *key;
 	struct ieee80211_sub_if_data *sdata;
 
@@ -51,24 +50,23 @@ static int ieee80211_set_encryption(struct net_device *dev, u8 *sta_addr,
 			key = sdata->keys[idx];
 		} else {
 			sta = sta_info_get(local, sta_addr);
-			if (!sta) {
-				ret = -ENOENT;
-				key = NULL;
-				goto err_out;
-			}
-
+			if (!sta)
+				return -ENOENT;
 			key = sta->key;
 		}
 
 		if (!key)
-			ret = -ENOENT;
-		else
-			ret = 0;
+			return -ENOENT;
+
+		ieee80211_key_free(key);
+		return 0;
 	} else {
 		key = ieee80211_key_alloc(alg, idx, key_len, _key);
 		if (!key)
 			return -ENOMEM;
 
+		sta = NULL;
+
 		if (!is_broadcast_ether_addr(sta_addr)) {
 			set_tx_key = 0;
 			/*
@@ -78,14 +76,14 @@ static int ieee80211_set_encryption(struct net_device *dev, u8 *sta_addr,
 			 * work around this.
 			 */
 			if (idx != 0 && alg != ALG_WEP) {
-				ret = -EINVAL;
-				goto err_out;
+				ieee80211_key_free(key);
+				return -EINVAL;
 			}
 
 			sta = sta_info_get(local, sta_addr);
 			if (!sta) {
-				ret = -ENOENT;
-				goto err_out;
+				ieee80211_key_free(key);
+				return -ENOENT;
 			}
 		}
 
@@ -93,18 +91,9 @@ static int ieee80211_set_encryption(struct net_device *dev, u8 *sta_addr,
 
 		if (set_tx_key || (!sta && !sdata->default_key && key))
 			ieee80211_set_default_key(sdata, idx);
-
-		/* don't free key later */
-		key = NULL;
-
-		ret = 0;
 	}
 
- err_out:
-	if (sta)
-		sta_info_put(sta);
-	ieee80211_key_free(key);
-	return ret;
+	return 0;
 }
 
 static int ieee80211_ioctl_siwgenie(struct net_device *dev,
@@ -625,7 +614,7 @@ static int ieee80211_ioctl_giwrate(struct net_device *dev,
 	else
 		rate->value = 0;
 	rate->value *= 100000;
-	sta_info_put(sta);
+
 	return 0;
 }
 
@@ -1000,7 +989,6 @@ static struct iw_statistics *ieee80211_get_wireless_stats(struct net_device *dev
 		wstats->qual.qual = sta->last_signal;
 		wstats->qual.noise = sta->last_noise;
 		wstats->qual.updated = local->wstats_flags;
-		sta_info_put(sta);
 	}
 	return wstats;
 }

net/mac80211/ieee80211_rate.c

@@ -170,9 +170,12 @@ void rate_control_get_rate(struct net_device *dev,
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
 	struct rate_control_ref *ref = local->rate_ctrl;
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
-	struct sta_info *sta = sta_info_get(local, hdr->addr1);
+	struct sta_info *sta;
 	int i;
 
+	rcu_read_lock();
+	sta = sta_info_get(local, hdr->addr1);
+
 	memset(sel, 0, sizeof(struct rate_selection));
 
 	ref->ops->get_rate(ref->priv, dev, sband, skb, sel);
@@ -190,8 +193,7 @@ void rate_control_get_rate(struct net_device *dev,
 		}
 	}
 
-	if (sta)
-		sta_info_put(sta);
+	rcu_read_unlock();
 }
 
 struct rate_control_ref *rate_control_get(struct rate_control_ref *ref)

net/mac80211/ieee80211_rate.h

@@ -14,6 +14,7 @@
 #include <linux/netdevice.h>
 #include <linux/skbuff.h>
 #include <linux/types.h>
+#include <linux/kref.h>
 #include <net/mac80211.h>
 #include "ieee80211_i.h"
 #include "sta_info.h"

net/mac80211/key.c

@@ -240,14 +240,17 @@ void ieee80211_key_link(struct ieee80211_key *key,
 		if (sdata->vif.type == IEEE80211_IF_TYPE_STA) {
 			struct sta_info *ap;
 
+			rcu_read_lock();
+
 			/* same here, the AP could be using QoS */
 			ap = sta_info_get(key->local, key->sdata->u.sta.bssid);
 			if (ap) {
 				if (ap->flags & WLAN_STA_WME)
 					key->conf.flags |=
 						IEEE80211_KEY_FLAG_WMM_STA;
-				sta_info_put(ap);
 			}
+
+			rcu_read_unlock();
 		}
 	}
 
@@ -290,6 +293,9 @@ void ieee80211_key_free(struct ieee80211_key *key)
 			__ieee80211_key_replace(key->sdata, key->sta,
 						key, NULL);
 
+		/*
+		 * Do NOT remove this without looking at sta_info_destroy()
+		 */
 		synchronize_rcu();
 
 		/*

net/mac80211/mesh.c

@@ -83,11 +83,10 @@ bool mesh_peer_accepts_plinks(struct ieee802_11_elems *ie,
 /**
  * mesh_accept_plinks_update: update accepting_plink in local mesh beacons
  *
- * @dev: mesh interface in which mesh beacons are going to be updated
+ * @sdata: mesh interface in which mesh beacons are going to be updated
  */
-void mesh_accept_plinks_update(struct net_device *dev)
+void mesh_accept_plinks_update(struct ieee80211_sub_if_data *sdata)
 {
-	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 	bool free_plinks;
 
 	/* In case mesh_plink_free_count > 0 and mesh_plinktbl_capacity == 0,

net/mac80211/mesh.h

@@ -65,9 +65,10 @@ enum mesh_path_flags {
  * @state_lock: mesh pat state lock
  *
  *
- * The combination of dst and dev is unique in the mesh path table. A reference
- * to the next_hop sta will be kept and in case this sta is removed, the
- * mesh_path structure must be also removed or substitued in a rcu safe way
+ * The combination of dst and dev is unique in the mesh path table. Since the
+ * next_hop STA is only protected by RCU as well, deleting the STA must also
+ * remove/substitute the mesh_path structure and wait until that is no longer
+ * reachable before destroying the STA completely.
  */
 struct mesh_path {
 	u8 dst[ETH_ALEN];
@@ -230,8 +231,9 @@ void mesh_neighbour_update(u8 *hw_addr, u64 rates, struct net_device *dev,
 		bool add);
 bool mesh_peer_accepts_plinks(struct ieee802_11_elems *ie,
 			      struct net_device *dev);
-void mesh_accept_plinks_update(struct net_device *dev);
-struct sta_info *mesh_plink_add(u8 *hw_addr, u64 rates, struct net_device *dev);
+void mesh_accept_plinks_update(struct ieee80211_sub_if_data *sdata);
+struct sta_info *mesh_plink_add(u8 *hw_addr, u64 rates,
+				struct ieee80211_sub_if_data *sdata);
 void mesh_plink_broken(struct sta_info *sta);
 void mesh_plink_deactivate(struct sta_info *sta);
 int mesh_plink_open(struct sta_info *sta);
@@ -254,7 +256,7 @@ void mesh_path_flush_pending(struct mesh_path *mpath);
 void mesh_path_tx_pending(struct mesh_path *mpath);
 int mesh_pathtbl_init(void);
 void mesh_pathtbl_unregister(void);
-int mesh_path_del(u8 *addr, struct net_device *dev);
+int mesh_path_del(u8 *addr, struct net_device *dev, bool force);
 void mesh_path_timer(unsigned long data);
 void mesh_path_flush_by_nexthop(struct sta_info *sta);
 void mesh_path_discard_frame(struct sk_buff *skb, struct net_device *dev);
@@ -270,7 +272,7 @@ static inline int mesh_plink_free_count(struct ieee80211_sub_if_data *sdata)
 
 static inline bool mesh_plink_availables(struct ieee80211_sub_if_data *sdata)
 {
-	return (min(mesh_plink_free_count(sdata),
+	return (min_t(long, mesh_plink_free_count(sdata),
 		   MESH_MAX_PLINKS - sdata->local->num_sta)) > 0;
 }
 

net/mac80211/mesh_hwmp.c

@@ -294,7 +294,6 @@ static u32 hwmp_route_info_get(struct net_device *dev,
 		orig_metric = PREP_IE_METRIC(hwmp_ie);
 		break;
 	default:
-		sta_info_put(sta);
 		rcu_read_unlock();
 		return 0;
 	}
@@ -330,7 +329,6 @@ static u32 hwmp_route_info_get(struct net_device *dev,
 			mpath = mesh_path_lookup(orig_addr, dev);
 			if (!mpath) {
 				rcu_read_unlock();
-				sta_info_put(sta);
 				return 0;
 			}
 			spin_lock_bh(&mpath->state_lock);
@@ -372,7 +370,6 @@ static u32 hwmp_route_info_get(struct net_device *dev,
 			mpath = mesh_path_lookup(ta, dev);
 			if (!mpath) {
 				rcu_read_unlock();
-				sta_info_put(sta);
 				return 0;
 			}
 			spin_lock_bh(&mpath->state_lock);
@@ -391,7 +388,6 @@ static u32 hwmp_route_info_get(struct net_device *dev,
 			spin_unlock_bh(&mpath->state_lock);
 	}
 
-	sta_info_put(sta);
 	rcu_read_unlock();
 
 	return process ? new_metric : 0;
@@ -861,5 +857,5 @@ void mesh_path_timer(unsigned long data)
 endmpathtimer:
 	rcu_read_unlock();
 	if (delete)
-		mesh_path_del(mpath->dst, mpath->dev);
+		mesh_path_del(mpath->dst, mpath->dev, false);
 }

net/mac80211/mesh_pathtbl.c

@@ -55,10 +55,7 @@ static DEFINE_RWLOCK(pathtbl_resize_lock);
  */
 void mesh_path_assign_nexthop(struct mesh_path *mpath, struct sta_info *sta)
 {
-	__sta_info_get(sta);
-	if (mpath->next_hop)
-		sta_info_put(mpath->next_hop);
-	mpath->next_hop = sta;
+	rcu_assign_pointer(mpath->next_hop, sta);
 }
 
 
@@ -236,7 +233,7 @@ void mesh_plink_broken(struct sta_info *sta)
 	struct mesh_path *mpath;
 	struct mpath_node *node;
 	struct hlist_node *p;
-	struct net_device *dev = sta->dev;
+	struct net_device *dev = sta->sdata->dev;
 	int i;
 
 	rcu_read_lock();
@@ -266,9 +263,9 @@ EXPORT_SYMBOL(mesh_plink_broken);
  *
  * RCU notes: this function is called when a mesh plink transitions from ESTAB
  * to any other state, since ESTAB state is the only one that allows path
- * creation. This will happen before the sta can be freed (since we hold
- * a reference to it) so any reader in a rcu read block will be protected
- * against the plink dissapearing.
+ * creation. This will happen before the sta can be freed (because
+ * sta_info_destroy() calls this) so any reader in a rcu read block will be
+ * protected against the plink disappearing.
  */
 void mesh_path_flush_by_nexthop(struct sta_info *sta)
 {
@@ -280,7 +277,7 @@ void mesh_path_flush_by_nexthop(struct sta_info *sta)
 	for_each_mesh_entry(mesh_paths, p, node, i) {
 		mpath = node->mpath;
 		if (mpath->next_hop == sta)
-			mesh_path_del(mpath->dst, mpath->dev);
+			mesh_path_del(mpath->dst, mpath->dev, true);
 	}
 }
 
@@ -294,7 +291,7 @@ void mesh_path_flush(struct net_device *dev)
 	for_each_mesh_entry(mesh_paths, p, node, i) {
 		mpath = node->mpath;
 		if (mpath->dev == dev)
-			mesh_path_del(mpath->dst, mpath->dev);
+			mesh_path_del(mpath->dst, mpath->dev, false);
 	}
 }
 
@@ -303,8 +300,8 @@ static void mesh_path_node_reclaim(struct rcu_head *rp)
 	struct mpath_node *node = container_of(rp, struct mpath_node, rcu);
 	struct ieee80211_sub_if_data *sdata =
 		IEEE80211_DEV_TO_SUB_IF(node->mpath->dev);
-	if (node->mpath->next_hop)
-		sta_info_put(node->mpath->next_hop);
+
+	rcu_assign_pointer(node->mpath->next_hop, NULL);
 	atomic_dec(&sdata->u.sta.mpaths);
 	kfree(node->mpath);
 	kfree(node);
@@ -319,9 +316,10 @@ static void mesh_path_node_reclaim(struct rcu_head *rp)
  * Returns: 0 if succesful
  *
  * State: if the path is being resolved, the deletion will be postponed until
- * the path resolution completes or times out.
+ * the path resolution completes or times out, unless the force parameter
+ * is given.
  */
-int mesh_path_del(u8 *addr, struct net_device *dev)
+int mesh_path_del(u8 *addr, struct net_device *dev, bool force)
 {
 	struct mesh_path *mpath;
 	struct mpath_node *node;
@@ -340,7 +338,7 @@ int mesh_path_del(u8 *addr, struct net_device *dev)
 		if (mpath->dev == dev &&
 				memcmp(addr, mpath->dst, ETH_ALEN) == 0) {
 			spin_lock_bh(&mpath->state_lock);
-			if (mpath->flags & MESH_PATH_RESOLVING) {
+			if (!force && mpath->flags & MESH_PATH_RESOLVING) {
 				mpath->flags |= MESH_PATH_DELETE;
 			} else {
 				mpath->flags |= MESH_PATH_RESOLVING;
@@ -510,7 +508,7 @@ void mesh_path_expire(struct net_device *dev)
 			time_after(jiffies,
 			 mpath->exp_time + MESH_PATH_EXPIRE)) {
 			spin_unlock_bh(&mpath->state_lock);
-			mesh_path_del(mpath->dst, mpath->dev);
+			mesh_path_del(mpath->dst, mpath->dev, false);
 		} else
 			spin_unlock_bh(&mpath->state_lock);
 	}

net/mac80211/rc80211_pid_algo.c

@@ -77,7 +77,7 @@ static void rate_control_pid_adjust_rate(struct ieee80211_local *local,
 	int cur_sorted, new_sorted, probe, tmp, n_bitrates, band;
 	int cur = sta->txrate_idx;
 
-	sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
+	sdata = sta->sdata;
 	sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
 	band = sband->band;
 	n_bitrates = sband->n_bitrates;
@@ -149,7 +149,7 @@ static void rate_control_pid_sample(struct rc_pid_info *pinfo,
 				    struct sta_info *sta)
 {
 #ifdef CONFIG_MAC80211_MESH
-	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
+	struct ieee80211_sub_if_data *sdata = sta->sdata;
 #endif
 	struct rc_pid_sta_info *spinfo = sta->rate_ctrl_priv;
 	struct rc_pid_rateinfo *rinfo = pinfo->rinfo;
@@ -249,23 +249,25 @@ static void rate_control_pid_tx_status(void *priv, struct net_device *dev,
 	unsigned long period;
 	struct ieee80211_supported_band *sband;
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, hdr->addr1);
 	sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
 
 	if (!sta)
-		return;
+		goto unlock;
 
 	/* Don't update the state if we're not controlling the rate. */
-	sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
+	sdata = sta->sdata;
 	if (sdata->bss && sdata->bss->force_unicast_rateidx > -1) {
 		sta->txrate_idx = sdata->bss->max_ratectrl_rateidx;
-		return;
+		goto unlock;
 	}
 
 	/* Ignore all frames that were sent with a different rate than the rate
 	 * we currently advise mac80211 to use. */
 	if (status->control.tx_rate != &sband->bitrates[sta->txrate_idx])
-		goto ignore;
+		goto unlock;
 
 	spinfo = sta->rate_ctrl_priv;
 	spinfo->tx_num_xmit++;
@@ -303,8 +305,8 @@ static void rate_control_pid_tx_status(void *priv, struct net_device *dev,
 	if (time_after(jiffies, spinfo->last_sample + period))
 		rate_control_pid_sample(pinfo, local, sta);
 
-ignore:
-	sta_info_put(sta);
+ unlock:
+	rcu_read_unlock();
 }
 
 static void rate_control_pid_get_rate(void *priv, struct net_device *dev,
@@ -319,6 +321,8 @@ static void rate_control_pid_get_rate(void *priv, struct net_device *dev,
 	int rateidx;
 	u16 fc;
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, hdr->addr1);
 
 	/* Send management frames and broadcast/multicast data using lowest
@@ -327,8 +331,7 @@ static void rate_control_pid_get_rate(void *priv, struct net_device *dev,
 	if ((fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA ||
 	    is_multicast_ether_addr(hdr->addr1) || !sta) {
 		sel->rate = rate_lowest(local, sband, sta);
-		if (sta)
-			sta_info_put(sta);
+		rcu_read_unlock();
 		return;
 	}
 
@@ -344,7 +347,7 @@ static void rate_control_pid_get_rate(void *priv, struct net_device *dev,
 
 	sta->last_txrate_idx = rateidx;
 
-	sta_info_put(sta);
+	rcu_read_unlock();
 
 	sel->rate = &sband->bitrates[rateidx];
 

net/mac80211/rc80211_simple.c

@@ -40,7 +40,7 @@ static void rate_control_rate_inc(struct ieee80211_local *local,
 	int i = sta->txrate_idx;
 	int maxrate;
 
-	sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
+	sdata = sta->sdata;
 	if (sdata->bss && sdata->bss->force_unicast_rateidx > -1) {
 		/* forced unicast rate - do not change STA rate */
 		return;
@@ -70,7 +70,7 @@ static void rate_control_rate_dec(struct ieee80211_local *local,
 	struct ieee80211_supported_band *sband;
 	int i = sta->txrate_idx;
 
-	sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
+	sdata = sta->sdata;
 	if (sdata->bss && sdata->bss->force_unicast_rateidx > -1) {
 		/* forced unicast rate - do not change STA rate */
 		return;
@@ -118,10 +118,12 @@ static void rate_control_simple_tx_status(void *priv, struct net_device *dev,
 	struct sta_info *sta;
 	struct sta_rate_control *srctrl;
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, hdr->addr1);
 
 	if (!sta)
-	    return;
+		goto unlock;
 
 	srctrl = sta->rate_ctrl_priv;
 	srctrl->tx_num_xmit++;
@@ -191,7 +193,8 @@ static void rate_control_simple_tx_status(void *priv, struct net_device *dev,
 		}
 	}
 
-	sta_info_put(sta);
+ unlock:
+	rcu_read_unlock();
 }
 
 
@@ -208,6 +211,8 @@ rate_control_simple_get_rate(void *priv, struct net_device *dev,
 	int rateidx;
 	u16 fc;
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, hdr->addr1);
 
 	/* Send management frames and broadcast/multicast data using lowest
@@ -216,8 +221,7 @@ rate_control_simple_get_rate(void *priv, struct net_device *dev,
 	if ((fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA ||
 	    is_multicast_ether_addr(hdr->addr1) || !sta) {
 		sel->rate = rate_lowest(local, sband, sta);
-		if (sta)
-			sta_info_put(sta);
+		rcu_read_unlock();
 		return;
 	}
 
@@ -233,7 +237,7 @@ rate_control_simple_get_rate(void *priv, struct net_device *dev,
 
 	sta->last_txrate_idx = rateidx;
 
-	sta_info_put(sta);
+	rcu_read_unlock();
 
 	sel->rate = &sband->bitrates[rateidx];
 }

net/mac80211/rx.c

@@ -631,7 +631,7 @@ static void ap_sta_ps_start(struct net_device *dev, struct sta_info *sta)
 	struct ieee80211_sub_if_data *sdata;
 	DECLARE_MAC_BUF(mac);
 
-	sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
+	sdata = sta->sdata;
 
 	if (sdata->bss)
 		atomic_inc(&sdata->bss->num_sta_ps);
@@ -652,7 +652,7 @@ static int ap_sta_ps_end(struct net_device *dev, struct sta_info *sta)
 	struct ieee80211_tx_packet_data *pkt_data;
 	DECLARE_MAC_BUF(mac);
 
-	sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
+	sdata = sta->sdata;
 
 	if (sdata->bss)
 		atomic_dec(&sdata->bss->num_sta_ps);
@@ -1287,7 +1287,7 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
 				       "multicast frame\n", dev->name);
 		} else {
 			dsta = sta_info_get(local, skb->data);
-			if (dsta && dsta->dev == dev) {
+			if (dsta && dsta->sdata->dev == dev) {
 				/*
 				 * The destination station is associated to
 				 * this AP (in this VLAN), so send the frame
@@ -1297,8 +1297,6 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
 				xmit_skb = skb;
 				skb = NULL;
 			}
-			if (dsta)
-				sta_info_put(dsta);
 		}
 	}
 
@@ -1905,13 +1903,13 @@ static void __ieee80211_rx_handle_packet(struct ieee80211_hw *hw,
 
 	rx.sta = sta_info_get(local, hdr->addr2);
 	if (rx.sta) {
-		rx.dev = rx.sta->dev;
-		rx.sdata = IEEE80211_DEV_TO_SUB_IF(rx.dev);
+		rx.sdata = rx.sta->sdata;
+		rx.dev = rx.sta->sdata->dev;
 	}
 
 	if ((status->flag & RX_FLAG_MMIC_ERROR)) {
 		ieee80211_rx_michael_mic_report(local->mdev, hdr, &rx);
-		goto end;
+		return;
 	}
 
 	if (unlikely(local->sta_sw_scanning || local->sta_hw_scanning))
@@ -1970,10 +1968,6 @@ static void __ieee80211_rx_handle_packet(struct ieee80211_hw *hw,
 		ieee80211_invoke_rx_handlers(prev, &rx, skb);
 	} else
 		dev_kfree_skb(skb);
-
- end:
-	if (rx.sta)
-		sta_info_put(rx.sta);
 }
 
 #define SEQ_MODULO 0x1000
@@ -2150,7 +2144,7 @@ static u8 ieee80211_rx_reorder_ampdu(struct ieee80211_local *local,
 	/* if this mpdu is fragmented - terminate rx aggregation session */
 	sc = le16_to_cpu(hdr->seq_ctrl);
 	if (sc & IEEE80211_SCTL_FRAG) {
-		ieee80211_sta_stop_rx_ba_session(sta->dev, sta->addr,
+		ieee80211_sta_stop_rx_ba_session(sta->sdata->dev, sta->addr,
 			tid, 0, WLAN_REASON_QSTA_REQUIRE_SETUP);
 		ret = 1;
 		goto end_reorder;
@@ -2160,9 +2154,7 @@ static u8 ieee80211_rx_reorder_ampdu(struct ieee80211_local *local,
 	mpdu_seq_num = (sc & IEEE80211_SCTL_SEQ) >> 4;
 	ret = ieee80211_sta_manage_reorder_buf(hw, tid_agg_rx, skb,
 						mpdu_seq_num, 0);
-end_reorder:
-	if (sta)
-		sta_info_put(sta);
+ end_reorder:
 	return ret;
 }
 

net/mac80211/sta_info.h

@@ -12,7 +12,6 @@
 #include <linux/list.h>
 #include <linux/types.h>
 #include <linux/if_ether.h>
-#include <linux/kref.h>
 #include "ieee80211_key.h"
 
 /**
@@ -134,8 +133,14 @@ struct sta_ampdu_mlme {
 	u8 dialog_token_allocator;
 };
 
+
+/* see __sta_info_unlink */
+#define STA_INFO_PIN_STAT_NORMAL	0
+#define STA_INFO_PIN_STAT_PINNED	1
+#define STA_INFO_PIN_STAT_DESTROY	2
+
+
 struct sta_info {
-	struct kref kref;
 	struct list_head list;
 	struct sta_info *hnext; /* next entry in hash table list */
 
@@ -166,8 +171,8 @@ struct sta_info {
 	/* last rates used to send a frame to this STA */
 	int last_txrate_idx, last_nonerp_txrate_idx;
 
-	struct net_device *dev; /* which net device is this station associated
-				 * to */
+	/* sub_if_data this sta belongs to */
+	struct ieee80211_sub_if_data *sdata;
 
 	struct ieee80211_key *key;
 
@@ -199,6 +204,12 @@ struct sta_info {
 
 	u16 listen_interval;
 
+	/*
+	 * for use by the internal lifetime management,
+	 * see __sta_info_unlink
+	 */
+	u8 pin_status;
+
 	struct ieee80211_ht_info ht_info; /* 802.11n HT capabilities
 					     of this STA */
 	struct sta_ampdu_mlme ampdu_mlme;
@@ -262,25 +273,37 @@ static inline enum plink_state sta_plink_state(struct sta_info *sta)
  */
 #define STA_INFO_CLEANUP_INTERVAL (10 * HZ)
 
-static inline void __sta_info_get(struct sta_info *sta)
-{
-	kref_get(&sta->kref);
-}
-
-struct sta_info * sta_info_get(struct ieee80211_local *local, u8 *addr);
+/*
+ * Get a STA info, must have be under RCU read lock.
+ */
+struct sta_info *sta_info_get(struct ieee80211_local *local, u8 *addr);
+/*
+ * Get STA info by index, BROKEN!
+ */
 struct sta_info *sta_info_get_by_idx(struct ieee80211_local *local, int idx,
 				      struct net_device *dev);
-void sta_info_put(struct sta_info *sta);
-struct sta_info *sta_info_add(struct ieee80211_local *local,
-			      struct net_device *dev, u8 *addr, gfp_t gfp);
-void sta_info_remove(struct sta_info *sta);
-void sta_info_free(struct sta_info *sta);
-void sta_info_init(struct ieee80211_local *local);
-int sta_info_start(struct ieee80211_local *local);
-void sta_info_stop(struct ieee80211_local *local);
-void sta_info_flush(struct ieee80211_local *local, struct net_device *dev);
+/*
+ * Add a new STA info, must be under RCU read lock
+ * because otherwise the returned reference isn't
+ * necessarily valid long enough.
+ */
+struct sta_info *sta_info_add(struct ieee80211_sub_if_data *sdata,
+			      u8 *addr);
+/*
+ * Unlink a STA info from the hash table/list.
+ * This can NULL the STA pointer if somebody else
+ * has already unlinked it.
+ */
+void sta_info_unlink(struct sta_info **sta);
 
+void sta_info_destroy(struct sta_info *sta);
 void sta_info_set_tim_bit(struct sta_info *sta);
 void sta_info_clear_tim_bit(struct sta_info *sta);
 
+void sta_info_init(struct ieee80211_local *local);
+int sta_info_start(struct ieee80211_local *local);
+void sta_info_stop(struct ieee80211_local *local);
+void sta_info_flush(struct ieee80211_local *local,
+		    struct ieee80211_sub_if_data *sdata);
+
 #endif /* STA_INFO_H */

net/mac80211/tx.c

@@ -327,10 +327,8 @@ static void purge_old_ps_buffers(struct ieee80211_local *local)
 		}
 		total += skb_queue_len(&ap->ps_bc_buf);
 	}
-	rcu_read_unlock();
 
-	read_lock_bh(&local->sta_lock);
-	list_for_each_entry(sta, &local->sta_list, list) {
+	list_for_each_entry_rcu(sta, &local->sta_list, list) {
 		skb = skb_dequeue(&sta->ps_tx_buf);
 		if (skb) {
 			purged++;
@@ -338,7 +336,8 @@ static void purge_old_ps_buffers(struct ieee80211_local *local)
 		}
 		total += skb_queue_len(&sta->ps_tx_buf);
 	}
-	read_unlock_bh(&local->sta_lock);
+
+	rcu_read_unlock();
 
 	local->total_ps_buffered = total;
 	printk(KERN_DEBUG "%s: PS buffers full - purged %d frames\n",
@@ -1141,20 +1140,17 @@ static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb,
 		return 0;
 	}
 
+	rcu_read_lock();
+
 	/* initialises tx */
 	res_prepare = __ieee80211_tx_prepare(&tx, skb, dev, control);
 
 	if (res_prepare == TX_DROP) {
 		dev_kfree_skb(skb);
+		rcu_read_unlock();
 		return 0;
 	}
 
-	/*
-	 * key references are protected using RCU and this requires that
-	 * we are in a read-site RCU section during receive processing
-	 */
-	rcu_read_lock();
-
 	sta = tx.sta;
 	tx.channel = local->hw.conf.channel;
 
@@ -1167,9 +1163,6 @@ static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb,
 
 	skb = tx.skb; /* handlers are allowed to change skb */
 
-	if (sta)
-		sta_info_put(sta);
-
 	if (unlikely(res == TX_DROP)) {
 		I802_DEBUG_INC(local->tx_handlers_drop);
 		goto drop;
@@ -1489,11 +1482,11 @@ int ieee80211_subif_start_xmit(struct sk_buff *skb,
 	 * in AP mode)
 	 */
 	if (!is_multicast_ether_addr(hdr.addr1)) {
+		rcu_read_lock();
 		sta = sta_info_get(local, hdr.addr1);
-		if (sta) {
+		if (sta)
 			sta_flags = sta->flags;
-			sta_info_put(sta);
-		}
+		rcu_read_unlock();
 	}
 
 	/* receiver is QoS enabled, use a QoS type frame */
@@ -1722,7 +1715,6 @@ static void ieee80211_beacon_add_tim(struct ieee80211_local *local,
 
 	/* Generate bitmap for TIM only if there are any STAs in power save
 	 * mode. */
-	read_lock_bh(&local->sta_lock);
 	if (atomic_read(&bss->num_sta_ps) > 0)
 		/* in the hope that this is faster than
 		 * checking byte-for-byte */
@@ -1773,7 +1765,6 @@ static void ieee80211_beacon_add_tim(struct ieee80211_local *local,
 		*pos++ = aid0; /* Bitmap control */
 		*pos++ = 0; /* Part Virt Bitmap */
 	}
-	read_unlock_bh(&local->sta_lock);
 }
 
 struct sk_buff *ieee80211_beacon_get(struct ieee80211_hw *hw,
@@ -1821,7 +1812,22 @@ struct sk_buff *ieee80211_beacon_get(struct ieee80211_hw *hw,
 			ieee80211_include_sequence(sdata,
 					(struct ieee80211_hdr *)skb->data);
 
-			ieee80211_beacon_add_tim(local, ap, skb, beacon);
+			/*
+			 * Not very nice, but we want to allow the driver to call
+			 * ieee80211_beacon_get() as a response to the set_tim()
+			 * callback. That, however, is already invoked under the
+			 * sta_lock to guarantee consistent and race-free update
+			 * of the tim bitmap in mac80211 and the driver.
+			 */
+			if (local->tim_in_locked_section) {
+				ieee80211_beacon_add_tim(local, ap, skb, beacon);
+			} else {
+				unsigned long flags;
+
+				spin_lock_irqsave(&local->sta_lock, flags);
+				ieee80211_beacon_add_tim(local, ap, skb, beacon);
+				spin_unlock_irqrestore(&local->sta_lock, flags);
+			}
 
 			if (beacon->tail)
 				memcpy(skb_put(skb, beacon->tail_len),
@@ -1965,7 +1971,6 @@ ieee80211_get_buffered_bc(struct ieee80211_hw *hw,
 		rcu_read_unlock();
 		return NULL;
 	}
-	rcu_read_unlock();
 
 	if (bss->dtim_count != 0)
 		return NULL; /* send buffered bc/mc only after DTIM beacon */
@@ -2010,8 +2015,7 @@ ieee80211_get_buffered_bc(struct ieee80211_hw *hw,
 		skb = NULL;
 	}
 
-	if (sta)
-		sta_info_put(sta);
+	rcu_read_unlock();
 
 	return skb;
 }

net/mac80211/wme.c

@@ -153,6 +153,7 @@ static int wme_qdiscop_enqueue(struct sk_buff *skb, struct Qdisc* qd)
 
 	if (pkt_data->flags & IEEE80211_TXPD_REQUEUE) {
 		queue = pkt_data->queue;
+		rcu_read_lock();
 		sta = sta_info_get(local, hdr->addr1);
 		tid = skb->priority & QOS_CONTROL_TAG1D_MASK;
 		if (sta) {
@@ -164,8 +165,8 @@ static int wme_qdiscop_enqueue(struct sk_buff *skb, struct Qdisc* qd)
 			} else {
 				pkt_data->flags &= ~IEEE80211_TXPD_AMPDU;
 			}
-			sta_info_put(sta);
 		}
+		rcu_read_unlock();
 		skb_queue_tail(&q->requeued[queue], skb);
 		qd->q.qlen++;
 		return 0;
@@ -187,6 +188,8 @@ static int wme_qdiscop_enqueue(struct sk_buff *skb, struct Qdisc* qd)
 		p++;
 		*p = 0;
 
+		rcu_read_lock();
+
 		sta = sta_info_get(local, hdr->addr1);
 		if (sta) {
 			int ampdu_queue = sta->tid_to_tx_q[tid];
@@ -197,8 +200,9 @@ static int wme_qdiscop_enqueue(struct sk_buff *skb, struct Qdisc* qd)
 			} else {
 				pkt_data->flags &= ~IEEE80211_TXPD_AMPDU;
 			}
-			sta_info_put(sta);
 		}
+
+		rcu_read_unlock();
 	}
 
 	if (unlikely(queue >= local->hw.queues)) {