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, 11 insertions, 7 deletions

diff --git a/net/mac80211/rc80211_simple.c b/net/mac80211/rc80211_simple.c
index bcc541d4b95c..4f72fdca7f12 100644
--- a/net/mac80211/rc80211_simple.c
+++ b/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];
 }