mac80211: split sta_info_add

sta_info_add() has two functions: allocating a station info
structure and inserting it into the hash table/list. Splitting
these two functions allows allocating with GFP_KERNEL in many
places instead of GFP_ATOMIC which is now required by the RCU
protection. Additionally, in many places RCU protection is now
no longer needed at all because between sta_info_alloc() and
sta_info_insert() the caller owns the structure.

This fixes a few race conditions with setting initial flags
and similar, but not all (see comments in ieee80211_sta.c and
cfg.c). More documentation on the existing races will be in
a follow-up patch.

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

1 files changed, 33 insertions, 9 deletions

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index e9ba6fcc0e45..6263cfc148c0 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -571,6 +571,12 @@ static void sta_apply_parameters(struct ieee80211_local *local,
         struct ieee80211_supported_band *sband;
         struct ieee80211_sub_if_data *sdata = sta->sdata;
 
+        /*
+         * FIXME: updating the flags is racy when this function is
+         *        called from ieee80211_change_station(), this will
+         *        be resolved in a future patch.
+         */
+
         if (params->station_flags & STATION_FLAG_CHANGED) {
                 sta->flags &= ~WLAN_STA_AUTHORIZED;
                 if (params->station_flags & STATION_FLAG_AUTHORIZED)
@@ -585,6 +591,13 @@ static void sta_apply_parameters(struct ieee80211_local *local,
                         sta->flags |= WLAN_STA_WME;
         }
 
+        /*
+         * FIXME: updating the following information is racy when this
+         *        function is called from ieee80211_change_station().
+         *        However, all this information should be static so
+         *        maybe we should just reject attemps to change it.
+         */
+
         if (params->aid) {
                 sta->aid = params->aid;
                 if (sta->aid > IEEE80211_MAX_AID)
@@ -626,6 +639,7 @@ static int ieee80211_add_station(struct wiphy *wiphy, struct net_device *dev,
         struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
         struct sta_info *sta;
         struct ieee80211_sub_if_data *sdata;
+        int err;
 
         /* Prevent a race with changing the rate control algorithm */
         if (!netif_running(dev))
@@ -641,16 +655,11 @@ 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, sdata);
+                sta = mesh_plink_alloc(sdata, mac, DEFAULT_RATES, GFP_KERNEL);
         else
-                sta = sta_info_add(sdata, mac);
-
-        if (IS_ERR(sta))
-                return PTR_ERR(sta);
-
-        if (sdata->vif.type == IEEE80211_IF_TYPE_VLAN ||
-            sdata->vif.type == IEEE80211_IF_TYPE_AP)
-                ieee80211_send_layer2_update(sta);
+                sta = sta_info_alloc(sdata, mac, GFP_KERNEL);
+        if (!sta)
+                return -ENOMEM;
 
         sta->flags = WLAN_STA_AUTH | WLAN_STA_ASSOC;
 
@@ -658,6 +667,21 @@ static int ieee80211_add_station(struct wiphy *wiphy, struct net_device *dev,
 
         rate_control_rate_init(sta, local);
 
+        rcu_read_lock();
+
+        err = sta_info_insert(sta);
+        if (err) {
+                sta_info_destroy(sta);
+                rcu_read_unlock();
+                return err;
+        }
+
+        if (sdata->vif.type == IEEE80211_IF_TYPE_VLAN ||
+            sdata->vif.type == IEEE80211_IF_TYPE_AP)
+                ieee80211_send_layer2_update(sta);
+
+        rcu_read_unlock();
+
         return 0;
 }