mac80211: fix race condition between assoc_done and first EAP packet

When associating to an AP, the station might miss the first EAP
packet that the AP sends due to a race condition between the association
success procedure and the rx flow in mac80211.
In such cases, the packet might fall in ieee80211_rx_h_check due to
the fact that the relevant rx->sta wasn't allocated yet.
Allocation of the relevant station info struct before actually
sending the association request and setting it with a new
dummy_sta flag solve this problem.
The station will accept only EAP packets from the AP while it
is in the pre-association/dummy state.
This dummy station entry is not seen by normal sta_info_get()
calls, only by sta_info_get_bss_rx().
The driver is not notified for the first insertion of the
dummy station. The driver is notified only after the association
is complete and the dummy flag is removed from the station entry.
That way, all the rest of the code flow should be untouched by
this change.

Signed-off-by: Guy Eilam <guy@wizery.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 137 insertions, 49 deletions

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index d469d9d2b499..17caba27040b 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -100,6 +100,27 @@ struct sta_info *sta_info_get(struct ieee80211_sub_if_data *sdata,
 				    lockdep_is_held(&local->sta_lock) ||
 				    lockdep_is_held(&local->sta_mtx));
 	while (sta) {
+		if (sta->sdata == sdata && !sta->dummy &&
+		    memcmp(sta->sta.addr, addr, ETH_ALEN) == 0)
+			break;
+		sta = rcu_dereference_check(sta->hnext,
+					    lockdep_is_held(&local->sta_lock) ||
+					    lockdep_is_held(&local->sta_mtx));
+	}
+	return sta;
+}
+
+/* get a station info entry even if it is a dummy station*/
+struct sta_info *sta_info_get_rx(struct ieee80211_sub_if_data *sdata,
+			      const u8 *addr)
+{
+	struct ieee80211_local *local = sdata->local;
+	struct sta_info *sta;
+
+	sta = rcu_dereference_check(local->sta_hash[STA_HASH(addr)],
+				    lockdep_is_held(&local->sta_lock) ||
+				    lockdep_is_held(&local->sta_mtx));
+	while (sta) {
 		if (sta->sdata == sdata &&
 		    memcmp(sta->sta.addr, addr, ETH_ALEN) == 0)
 			break;
@@ -126,6 +147,32 @@ struct sta_info *sta_info_get_bss(struct ieee80211_sub_if_data *sdata,
 	while (sta) {
 		if ((sta->sdata == sdata ||
 		     (sta->sdata->bss && sta->sdata->bss == sdata->bss)) &&
+		    !sta->dummy &&
+		    memcmp(sta->sta.addr, addr, ETH_ALEN) == 0)
+			break;
+		sta = rcu_dereference_check(sta->hnext,
+					    lockdep_is_held(&local->sta_lock) ||
+					    lockdep_is_held(&local->sta_mtx));
+	}
+	return sta;
+}
+
+/*
+ * Get sta info either from the specified interface
+ * or from one of its vlans (including dummy stations)
+ */
+struct sta_info *sta_info_get_bss_rx(struct ieee80211_sub_if_data *sdata,
+				  const u8 *addr)
+{
+	struct ieee80211_local *local = sdata->local;
+	struct sta_info *sta;
+
+	sta = rcu_dereference_check(local->sta_hash[STA_HASH(addr)],
+				    lockdep_is_held(&local->sta_lock) ||
+				    lockdep_is_held(&local->sta_mtx));
+	while (sta) {
+		if ((sta->sdata == sdata ||
+		     (sta->sdata->bss && sta->sdata->bss == sdata->bss)) &&
 		    memcmp(sta->sta.addr, addr, ETH_ALEN) == 0)
 			break;
 		sta = rcu_dereference_check(sta->hnext,
@@ -280,7 +327,8 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
 	return sta;
 }
 
-static int sta_info_finish_insert(struct sta_info *sta, bool async)
+static int sta_info_finish_insert(struct sta_info *sta,
+				bool async, bool dummy_reinsert)
 {
 	struct ieee80211_local *local = sta->local;
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
@@ -290,51 +338,58 @@ static int sta_info_finish_insert(struct sta_info *sta, bool async)
 
 	lockdep_assert_held(&local->sta_mtx);
 
-	/* notify driver */
-	if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
-		sdata = container_of(sdata->bss,
-				     struct ieee80211_sub_if_data,
-				     u.ap);
-	err = drv_sta_add(local, sdata, &sta->sta);
-	if (err) {
-		if (!async)
-			return err;
-		printk(KERN_DEBUG "%s: failed to add IBSS STA %pM to driver (%d)"
-				  " - keeping it anyway.\n",
-		       sdata->name, sta->sta.addr, err);
-	} else {
-		sta->uploaded = true;
+	if (!sta->dummy || dummy_reinsert) {
+		/* notify driver */
+		if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
+			sdata = container_of(sdata->bss,
+					     struct ieee80211_sub_if_data,
+					     u.ap);
+		err = drv_sta_add(local, sdata, &sta->sta);
+		if (err) {
+			if (!async)
+				return err;
+			printk(KERN_DEBUG "%s: failed to add IBSS STA %pM to "
+					  "driver (%d) - keeping it anyway.\n",
+			       sdata->name, sta->sta.addr, err);
+		} else {
+			sta->uploaded = true;
 #ifdef CONFIG_MAC80211_VERBOSE_DEBUG
-		if (async)
-			wiphy_debug(local->hw.wiphy,
-				    "Finished adding IBSS STA %pM\n",
-				    sta->sta.addr);
+			if (async)
+				wiphy_debug(local->hw.wiphy,
+					    "Finished adding IBSS STA %pM\n",
+					    sta->sta.addr);
 #endif
+		}
+
+		sdata = sta->sdata;
 	}
 
-	sdata = sta->sdata;
+	if (!dummy_reinsert) {
+		if (!async) {
+			local->num_sta++;
+			local->sta_generation++;
+			smp_mb();
 
-	if (!async) {
-		local->num_sta++;
-		local->sta_generation++;
-		smp_mb();
+			/* make the station visible */
+			spin_lock_irqsave(&local->sta_lock, flags);
+			sta_info_hash_add(local, sta);
+			spin_unlock_irqrestore(&local->sta_lock, flags);
+		}
 
-		/* make the station visible */
-		spin_lock_irqsave(&local->sta_lock, flags);
-		sta_info_hash_add(local, sta);
-		spin_unlock_irqrestore(&local->sta_lock, flags);
+		list_add(&sta->list, &local->sta_list);
+	} else {
+		sta->dummy = false;
 	}
 
-	list_add(&sta->list, &local->sta_list);
-
-	ieee80211_sta_debugfs_add(sta);
-	rate_control_add_sta_debugfs(sta);
-
-	memset(&sinfo, 0, sizeof(sinfo));
-	sinfo.filled = 0;
-	sinfo.generation = local->sta_generation;
-	cfg80211_new_sta(sdata->dev, sta->sta.addr, &sinfo, GFP_KERNEL);
+	if (!sta->dummy) {
+		ieee80211_sta_debugfs_add(sta);
+		rate_control_add_sta_debugfs(sta);
 
+		memset(&sinfo, 0, sizeof(sinfo));
+		sinfo.filled = 0;
+		sinfo.generation = local->sta_generation;
+		cfg80211_new_sta(sdata->dev, sta->sta.addr, &sinfo, GFP_KERNEL);
+	}
 
 	return 0;
 }
@@ -351,7 +406,7 @@ static void sta_info_finish_pending(struct ieee80211_local *local)
 		list_del(&sta->list);
 		spin_unlock_irqrestore(&local->sta_lock, flags);
 
-		sta_info_finish_insert(sta, true);
+		sta_info_finish_insert(sta, true, false);
 
 		spin_lock_irqsave(&local->sta_lock, flags);
 	}
@@ -395,7 +450,7 @@ static int sta_info_insert_ibss(struct sta_info *sta) __acquires(RCU)
 
 	spin_lock_irqsave(&local->sta_lock, flags);
 	/* check if STA exists already */
-	if (sta_info_get_bss(sdata, sta->sta.addr)) {
+	if (sta_info_get_bss_rx(sdata, sta->sta.addr)) {
 		spin_unlock_irqrestore(&local->sta_lock, flags);
 		rcu_read_lock();
 		return -EEXIST;
@@ -431,6 +486,8 @@ static int sta_info_insert_non_ibss(struct sta_info *sta) __acquires(RCU)
 	struct ieee80211_local *local = sta->local;
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
 	unsigned long flags;
+	struct sta_info *exist_sta;
+	bool dummy_reinsert = false;
 	int err = 0;
 
 	lockdep_assert_held(&local->sta_mtx);
@@ -446,17 +503,28 @@ static int sta_info_insert_non_ibss(struct sta_info *sta) __acquires(RCU)
 	 */
 
 	spin_lock_irqsave(&local->sta_lock, flags);
-	/* check if STA exists already */
-	if (sta_info_get_bss(sdata, sta->sta.addr)) {
-		spin_unlock_irqrestore(&local->sta_lock, flags);
-		mutex_unlock(&local->sta_mtx);
-		rcu_read_lock();
-		return -EEXIST;
+	/*
+	 * check if STA exists already.
+	 * only accept a scenario of a second call to sta_info_insert_non_ibss
+	 * with a dummy station entry that was inserted earlier
+	 * in that case - assume that the dummy station flag should
+	 * be removed.
+	 */
+	exist_sta = sta_info_get_bss_rx(sdata, sta->sta.addr);
+	if (exist_sta) {
+		if (exist_sta == sta && sta->dummy) {
+			dummy_reinsert = true;
+		} else {
+			spin_unlock_irqrestore(&local->sta_lock, flags);
+			mutex_unlock(&local->sta_mtx);
+			rcu_read_lock();
+			return -EEXIST;
+		}
 	}
 
 	spin_unlock_irqrestore(&local->sta_lock, flags);
 
-	err = sta_info_finish_insert(sta, false);
+	err = sta_info_finish_insert(sta, false, dummy_reinsert);
 	if (err) {
 		mutex_unlock(&local->sta_mtx);
 		rcu_read_lock();
@@ -464,7 +532,8 @@ static int sta_info_insert_non_ibss(struct sta_info *sta) __acquires(RCU)
 	}
 
 #ifdef CONFIG_MAC80211_VERBOSE_DEBUG
-	wiphy_debug(local->hw.wiphy, "Inserted STA %pM\n", sta->sta.addr);
+	wiphy_debug(local->hw.wiphy, "Inserted %sSTA %pM\n",
+			sta->dummy ? "dummy " : "", sta->sta.addr);
 #endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
 
 	/* move reference to rcu-protected */
@@ -535,6 +604,25 @@ int sta_info_insert(struct sta_info *sta)
 	return err;
 }
 
+/* Caller must hold sta->local->sta_mtx */
+int sta_info_reinsert(struct sta_info *sta)
+{
+	struct ieee80211_local *local = sta->local;
+	int err = 0;
+
+	err = sta_info_insert_check(sta);
+	if (err) {
+		mutex_unlock(&local->sta_mtx);
+		return err;
+	}
+
+	might_sleep();
+
+	err = sta_info_insert_non_ibss(sta);
+	rcu_read_unlock();
+	return err;
+}
+
 static inline void __bss_tim_set(struct ieee80211_if_ap *bss, u16 aid)
 {
 	/*
@@ -775,7 +863,7 @@ int sta_info_destroy_addr(struct ieee80211_sub_if_data *sdata, const u8 *addr)
 	int ret;
 
 	mutex_lock(&sdata->local->sta_mtx);
-	sta = sta_info_get(sdata, addr);
+	sta = sta_info_get_rx(sdata, addr);
 	ret = __sta_info_destroy(sta);
 	mutex_unlock(&sdata->local->sta_mtx);
 
@@ -789,7 +877,7 @@ int sta_info_destroy_addr_bss(struct ieee80211_sub_if_data *sdata,
 	int ret;
 
 	mutex_lock(&sdata->local->sta_mtx);
-	sta = sta_info_get_bss(sdata, addr);
+	sta = sta_info_get_bss_rx(sdata, addr);
 	ret = __sta_info_destroy(sta);
 	mutex_unlock(&sdata->local->sta_mtx);