5 files changed, 64 insertions, 31 deletions

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 6b183a3526b0..fbd462c78e18 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -672,7 +672,7 @@ static int ieee80211_add_station(struct wiphy *wiphy, struct net_device *dev,
 
         err = sta_info_insert(sta);
         if (err) {
-                sta_info_destroy(sta);
+                /* STA has been freed */
                 rcu_read_unlock();
                 return err;
         }
diff --git a/net/mac80211/ieee80211.c b/net/mac80211/ieee80211.c
index 8c0f782d21e3..5ee431b6256c 100644
--- a/net/mac80211/ieee80211.c
+++ b/net/mac80211/ieee80211.c
@@ -268,7 +268,7 @@ static int ieee80211_open(struct net_device *dev)
 
                 res = sta_info_insert(sta);
                 if (res) {
-                        sta_info_destroy(sta);
+                        /* STA has been freed */
                         return res;
                 }
                 break;
diff --git a/net/mac80211/ieee80211_sta.c b/net/mac80211/ieee80211_sta.c
index baa68575b98a..00fde111c268 100644
--- a/net/mac80211/ieee80211_sta.c
+++ b/net/mac80211/ieee80211_sta.c
@@ -1942,7 +1942,6 @@ static void ieee80211_rx_mgmt_assoc_resp(struct ieee80211_sub_if_data *sdata,
                 if (err) {
                         printk(KERN_DEBUG "%s: failed to insert STA entry for"
                                " the AP (error %d)\n", dev->name, err);
-                        sta_info_destroy(sta);
                         rcu_read_unlock();
                         return;
                 }
@@ -4172,10 +4171,8 @@ struct sta_info * ieee80211_ibss_add_sta(struct net_device *dev,
 
         rate_control_rate_init(sta, local);
 
-        if (sta_info_insert(sta)) {
-                sta_info_destroy(sta);
+        if (sta_info_insert(sta))
                 return NULL;
-        }
 
         return sta;
 }
diff --git a/net/mac80211/mesh_plink.c b/net/mac80211/mesh_plink.c
index 18fe52436c47..56c54e321b38 100644
--- a/net/mac80211/mesh_plink.c
+++ b/net/mac80211/mesh_plink.c
@@ -89,6 +89,10 @@ static inline void mesh_plink_fsm_restart(struct sta_info *sta)
         sta->plink_retries = 0;
 }
 
+/*
+ * NOTE: This is just an alias for sta_info_alloc(), see notes
+ *       on it in the lifecycle management section!
+ */
 static struct sta_info *mesh_plink_alloc(struct ieee80211_sub_if_data *sdata,
                                          u8 *hw_addr, u64 rates)
 {
@@ -235,7 +239,6 @@ void mesh_neighbour_update(u8 *hw_addr, u64 rates, struct net_device *dev,
                         return;
                 }
                 if (sta_info_insert(sta)) {
-                        sta_info_destroy(sta);
                         rcu_read_unlock();
                         return;
                 }
@@ -506,7 +509,6 @@ void mesh_rx_plink_frame(struct net_device *dev, struct ieee80211_mgmt *mgmt,
                         return;
                 }
                 if (sta_info_insert(sta)) {
-                        sta_info_destroy(sta);
                         rcu_read_unlock();
                         return;
                 }
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 2a5a2f067bae..5497ca1843fe 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -36,16 +36,23 @@
  * (which is pretty useless) or insert it into the hash table using
  * sta_info_insert() which demotes the reference from ownership to a regular
  * RCU-protected reference; if the function is called without protection by an
- * RCU critical section the reference is instantly invalidated.
+ * RCU critical section the reference is instantly invalidated. Note that the
+ * caller may not do much with the STA info before inserting it, in particular,
+ * it may not start any mesh peer link management or add encryption keys.
+ *
+ * When the insertion fails (sta_info_insert()) returns non-zero), the
+ * structure will have been freed by sta_info_insert()!
  *
  * Because there are debugfs entries for each station, and adding those
  * must be able to sleep, it is also possible to "pin" a station entry,
  * that means it can be removed from the hash table but not be freed.
- * See the comment in __sta_info_unlink() for more information.
+ * See the comment in __sta_info_unlink() for more information, this is
+ * an internal capability only.
  *
  * In order to remove a STA info structure, the caller needs to first
  * unlink it (sta_info_unlink()) from the list and hash tables and
- * then wait for an RCU synchronisation before it can be freed. Due to
+ * then destroy it while holding the RTNL; sta_info_destroy() will wait
+ * for an RCU grace period to elapse before actually freeing it. Due to
  * the pinning and the possibility of multiple callers trying to remove
  * the same STA info at the same time, sta_info_unlink() can clear the
  * STA info pointer it is passed to indicate that the STA info is owned
@@ -127,12 +134,35 @@ struct sta_info *sta_info_get_by_idx(struct ieee80211_local *local, int idx,
         return NULL;
 }
 
+/**
+ * __sta_info_free - internal STA free helper
+ *
+ * @sta: STA info to free
+ *
+ * This function must undo everything done by sta_info_alloc()
+ * that may happen before sta_info_insert().
+ */
+static void __sta_info_free(struct ieee80211_local *local,
+                            struct sta_info *sta)
+{
+        DECLARE_MAC_BUF(mbuf);
+
+        rate_control_free_sta(sta->rate_ctrl, sta->rate_ctrl_priv);
+        rate_control_put(sta->rate_ctrl);
+
+#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
+        printk(KERN_DEBUG "%s: Destroyed STA %s\n",
+               wiphy_name(local->hw.wiphy), print_mac(mbuf, sta->addr));
+#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
+
+        kfree(sta);
+}
+
 void sta_info_destroy(struct sta_info *sta)
 {
         struct ieee80211_local *local;
         struct sk_buff *skb;
         int i;
-        DECLARE_MAC_BUF(mbuf);
 
         ASSERT_RTNL();
         might_sleep();
@@ -182,15 +212,7 @@ void sta_info_destroy(struct sta_info *sta)
                 spin_unlock_bh(&sta->ampdu_mlme.ampdu_tx);
         }
 
-        rate_control_free_sta(sta->rate_ctrl, sta->rate_ctrl_priv);
-        rate_control_put(sta->rate_ctrl);
-
-#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
-        printk(KERN_DEBUG "%s: Destroyed STA %s\n",
-               wiphy_name(local->hw.wiphy), print_mac(mbuf, sta->addr));
-#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
-
-        kfree(sta);
+        __sta_info_free(local, sta);
 }
 
 
@@ -266,6 +288,7 @@ int sta_info_insert(struct sta_info *sta)
         struct ieee80211_local *local = sta->local;
         struct ieee80211_sub_if_data *sdata = sta->sdata;
         unsigned long flags;
+        int err = 0;
         DECLARE_MAC_BUF(mac);
 
         /*
@@ -273,20 +296,23 @@ int sta_info_insert(struct sta_info *sta)
          * something inserts a STA (on one CPU) without holding the RTNL
          * and another CPU turns off the net device.
          */
-        if (unlikely(!netif_running(sdata->dev)))
-                return -ENETDOWN;
-
-        if (WARN_ON(compare_ether_addr(sta->addr, sdata->dev->dev_addr) == 0))
-                return -EINVAL;
+        if (unlikely(!netif_running(sdata->dev))) {
+                err = -ENETDOWN;
+                goto out_free;
+        }
 
-        if (WARN_ON(is_multicast_ether_addr(sta->addr)))
-                return -EINVAL;
+        if (WARN_ON(compare_ether_addr(sta->addr, sdata->dev->dev_addr) == 0 ||
+                    is_multicast_ether_addr(sta->addr))) {
+                err = -EINVAL;
+                goto out_free;
+        }
 
         spin_lock_irqsave(&local->sta_lock, flags);
         /* check if STA exists already */
         if (__sta_info_find(local, sta->addr)) {
                 spin_unlock_irqrestore(&local->sta_lock, flags);
-                return -EEXIST;
+                err = -EEXIST;
+                goto out_free;
         }
         list_add(&sta->list, &local->sta_list);
         local->num_sta++;
@@ -309,9 +335,13 @@ int sta_info_insert(struct sta_info *sta)
         spin_unlock_irqrestore(&local->sta_lock, flags);
 
 #ifdef CONFIG_MAC80211_DEBUGFS
-        /* debugfs entry adding might sleep, so schedule process
+        /*
+         * Debugfs entry adding might sleep, so schedule process
          * context task for adding entry for STAs that do not yet
-         * have one. */
+         * have one.
+         * NOTE: due to auto-freeing semantics this may only be done
+         *       if the insertion is successful!
+         */
         queue_work(local->hw.workqueue, &local->sta_debugfs_add);
 #endif
 
@@ -319,6 +349,10 @@ int sta_info_insert(struct sta_info *sta)
                 mesh_accept_plinks_update(sdata);
 
         return 0;
+ out_free:
+        BUG_ON(!err);
+        __sta_info_free(local, sta);
+        return err;
 }
 
 static inline void __bss_tim_set(struct ieee80211_if_ap *bss, u16 aid)