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, 15 insertions, 12 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-4965-rs.c b/drivers/net/wireless/iwlwifi/iwl-4965-rs.c
index 48a6a85355ec..46d85fd07faa 100644
--- a/drivers/net/wireless/iwlwifi/iwl-4965-rs.c
+++ b/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;
 }