mac80211: fix TX aggregation start/stop callback race

When starting or stopping an aggregation session, one of the steps
is that the driver calls back to mac80211 that the start/stop can
proceed. This is handled by queueing up a fake SKB and processing
it from the normal iface/sdata work. Since this isn't flushed when
disassociating, the following race is possible:

 * associate
 * start aggregation session
 * driver callback
 * disassociate
 * associate again to the same AP
 * callback processing runs, leading to a WARN_ON() that
   the TID hadn't requested aggregation

If the second association isn't to the same AP, there would only
be a message printed ("Could not find station: <addr>"), but the
same race could happen.

Fix this by not going the whole detour with a fake SKB etc. but
simply looking up the aggregation session in the driver callback,
marking it with a START_CB/STOP_CB bit and then scheduling the
regular aggregation work that will now process these bits as well.
This also simplifies the code and gets rid of the whole problem
with allocation failures of said skb, which could have left the
session in limbo.

Reported-by: Jouni Malinen <j@w1.fi>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 52 insertions, 76 deletions

diff --git a/net/mac80211/agg-tx.c b/net/mac80211/agg-tx.c
index 60e2a62f7bef..cf2392b2ac71 100644
--- a/net/mac80211/agg-tx.c
+++ b/net/mac80211/agg-tx.c
@@ -7,7 +7,7 @@
  * Copyright 2006-2007	Jiri Benc <jbenc@suse.cz>
  * Copyright 2007, Michael Wu <flamingice@sourmilk.net>
  * Copyright 2007-2010, Intel Corporation
- * Copyright(c) 2015 Intel Deutschland GmbH
+ * Copyright(c) 2015-2017 Intel Deutschland GmbH
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
@@ -741,46 +741,43 @@ static void ieee80211_agg_tx_operational(struct ieee80211_local *local,
 	ieee80211_agg_start_txq(sta, tid, true);
 }
 
-void ieee80211_start_tx_ba_cb(struct ieee80211_vif *vif, u8 *ra, u16 tid)
+void ieee80211_start_tx_ba_cb(struct sta_info *sta, int tid,
+			      struct tid_ampdu_tx *tid_tx)
 {
-	struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
+	struct ieee80211_sub_if_data *sdata = sta->sdata;
 	struct ieee80211_local *local = sdata->local;
-	struct sta_info *sta;
-	struct tid_ampdu_tx *tid_tx;
 
-	trace_api_start_tx_ba_cb(sdata, ra, tid);
+	if (WARN_ON(test_and_set_bit(HT_AGG_STATE_DRV_READY, &tid_tx->state)))
+		return;
+
+	if (test_bit(HT_AGG_STATE_RESPONSE_RECEIVED, &tid_tx->state))
+		ieee80211_agg_tx_operational(local, sta, tid);
+}
+
+static struct tid_ampdu_tx *
+ieee80211_lookup_tid_tx(struct ieee80211_sub_if_data *sdata,
+			const u8 *ra, u16 tid, struct sta_info **sta)
+{
+	struct tid_ampdu_tx *tid_tx;
 
 	if (tid >= IEEE80211_NUM_TIDS) {
 		ht_dbg(sdata, "Bad TID value: tid = %d (>= %d)\n",
 		       tid, IEEE80211_NUM_TIDS);
-		return;
+		return NULL;
 	}
 
-	mutex_lock(&local->sta_mtx);
-	sta = sta_info_get_bss(sdata, ra);
-	if (!sta) {
-		mutex_unlock(&local->sta_mtx);
+	*sta = sta_info_get_bss(sdata, ra);
+	if (!*sta) {
 		ht_dbg(sdata, "Could not find station: %pM\n", ra);
-		return;
+		return NULL;
 	}
 
-	mutex_lock(&sta->ampdu_mlme.mtx);
-	tid_tx = rcu_dereference_protected_tid_tx(sta, tid);
+	tid_tx = rcu_dereference((*sta)->ampdu_mlme.tid_tx[tid]);
 
-	if (WARN_ON(!tid_tx)) {
+	if (WARN_ON(!tid_tx))
 		ht_dbg(sdata, "addBA was not requested!\n");
-		goto unlock;
-	}
 
-	if (WARN_ON(test_and_set_bit(HT_AGG_STATE_DRV_READY, &tid_tx->state)))
-		goto unlock;
-
-	if (test_bit(HT_AGG_STATE_RESPONSE_RECEIVED, &tid_tx->state))
-		ieee80211_agg_tx_operational(local, sta, tid);
-
- unlock:
-	mutex_unlock(&sta->ampdu_mlme.mtx);
-	mutex_unlock(&local->sta_mtx);
+	return tid_tx;
 }
 
 void ieee80211_start_tx_ba_cb_irqsafe(struct ieee80211_vif *vif,
@@ -788,19 +785,20 @@ void ieee80211_start_tx_ba_cb_irqsafe(struct ieee80211_vif *vif,
 {
 	struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
 	struct ieee80211_local *local = sdata->local;
-	struct ieee80211_ra_tid *ra_tid;
-	struct sk_buff *skb = dev_alloc_skb(0);
+	struct sta_info *sta;
+	struct tid_ampdu_tx *tid_tx;
 
-	if (unlikely(!skb))
-		return;
+	trace_api_start_tx_ba_cb(sdata, ra, tid);
 
-	ra_tid = (struct ieee80211_ra_tid *) &skb->cb;
-	memcpy(&ra_tid->ra, ra, ETH_ALEN);
-	ra_tid->tid = tid;
+	rcu_read_lock();
+	tid_tx = ieee80211_lookup_tid_tx(sdata, ra, tid, &sta);
+	if (!tid_tx)
+		goto out;
 
-	skb->pkt_type = IEEE80211_SDATA_QUEUE_AGG_START;
-	skb_queue_tail(&sdata->skb_queue, skb);
-	ieee80211_queue_work(&local->hw, &sdata->work);
+	set_bit(HT_AGG_STATE_START_CB, &tid_tx->state);
+	ieee80211_queue_work(&local->hw, &sta->ampdu_mlme.work);
+ out:
+	rcu_read_unlock();
 }
 EXPORT_SYMBOL(ieee80211_start_tx_ba_cb_irqsafe);
 
@@ -860,37 +858,18 @@ int ieee80211_stop_tx_ba_session(struct ieee80211_sta *pubsta, u16 tid)
 }
 EXPORT_SYMBOL(ieee80211_stop_tx_ba_session);
 
-void ieee80211_stop_tx_ba_cb(struct ieee80211_vif *vif, u8 *ra, u8 tid)
+void ieee80211_stop_tx_ba_cb(struct sta_info *sta, int tid,
+			     struct tid_ampdu_tx *tid_tx)
 {
-	struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
-	struct ieee80211_local *local = sdata->local;
-	struct sta_info *sta;
-	struct tid_ampdu_tx *tid_tx;
+	struct ieee80211_sub_if_data *sdata = sta->sdata;
 	bool send_delba = false;
 
-	trace_api_stop_tx_ba_cb(sdata, ra, tid);
-
-	if (tid >= IEEE80211_NUM_TIDS) {
-		ht_dbg(sdata, "Bad TID value: tid = %d (>= %d)\n",
-		       tid, IEEE80211_NUM_TIDS);
-		return;
-	}
-
-	ht_dbg(sdata, "Stopping Tx BA session for %pM tid %d\n", ra, tid);
-
-	mutex_lock(&local->sta_mtx);
-
-	sta = sta_info_get_bss(sdata, ra);
-	if (!sta) {
-		ht_dbg(sdata, "Could not find station: %pM\n", ra);
-		goto unlock;
-	}
+	ht_dbg(sdata, "Stopping Tx BA session for %pM tid %d\n",
+	       sta->sta.addr, tid);
 
-	mutex_lock(&sta->ampdu_mlme.mtx);
 	spin_lock_bh(&sta->lock);
-	tid_tx = rcu_dereference_protected_tid_tx(sta, tid);
 
-	if (!tid_tx || !test_bit(HT_AGG_STATE_STOPPING, &tid_tx->state)) {
+	if (!test_bit(HT_AGG_STATE_STOPPING, &tid_tx->state)) {
 		ht_dbg(sdata,
 		       "unexpected callback to A-MPDU stop for %pM tid %d\n",
 		       sta->sta.addr, tid);
@@ -906,12 +885,8 @@ void ieee80211_stop_tx_ba_cb(struct ieee80211_vif *vif, u8 *ra, u8 tid)
 	spin_unlock_bh(&sta->lock);
 
 	if (send_delba)
-		ieee80211_send_delba(sdata, ra, tid,
+		ieee80211_send_delba(sdata, sta->sta.addr, tid,
 			WLAN_BACK_INITIATOR, WLAN_REASON_QSTA_NOT_USE);
-
-	mutex_unlock(&sta->ampdu_mlme.mtx);
- unlock:
-	mutex_unlock(&local->sta_mtx);
 }
 
 void ieee80211_stop_tx_ba_cb_irqsafe(struct ieee80211_vif *vif,
@@ -919,19 +894,20 @@ void ieee80211_stop_tx_ba_cb_irqsafe(struct ieee80211_vif *vif,
 {
 	struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
 	struct ieee80211_local *local = sdata->local;
-	struct ieee80211_ra_tid *ra_tid;
-	struct sk_buff *skb = dev_alloc_skb(0);
+	struct sta_info *sta;
+	struct tid_ampdu_tx *tid_tx;
 
-	if (unlikely(!skb))
-		return;
+	trace_api_stop_tx_ba_cb(sdata, ra, tid);
 
-	ra_tid = (struct ieee80211_ra_tid *) &skb->cb;
-	memcpy(&ra_tid->ra, ra, ETH_ALEN);
-	ra_tid->tid = tid;
+	rcu_read_lock();
+	tid_tx = ieee80211_lookup_tid_tx(sdata, ra, tid, &sta);
+	if (!tid_tx)
+		goto out;
 
-	skb->pkt_type = IEEE80211_SDATA_QUEUE_AGG_STOP;
-	skb_queue_tail(&sdata->skb_queue, skb);
-	ieee80211_queue_work(&local->hw, &sdata->work);
+	set_bit(HT_AGG_STATE_STOP_CB, &tid_tx->state);
+	ieee80211_queue_work(&local->hw, &sta->ampdu_mlme.work);
+ out:
+	rcu_read_unlock();
 }
 EXPORT_SYMBOL(ieee80211_stop_tx_ba_cb_irqsafe);