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, 14 insertions, 11 deletions

diff --git a/net/mac80211/rc80211_pid_algo.c b/net/mac80211/rc80211_pid_algo.c
index 217c0f487bb..a1993161de9 100644
--- a/net/mac80211/rc80211_pid_algo.c
+++ b/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];