mac80211: fix spurious delBA handling

commit 827d42c9ac91ddd728e4f4a31fefb906ef2ceff7 upstream.

Lennert Buytenhek noticed that delBA handling in mac80211
was broken and has remotely triggerable problems, some of
which are due to some code shuffling I did that ended up
changing the order in which things were done -- this was

  commit d75636ef9c1af224f1097941879d5a8db7cd04e5
  Author: Johannes Berg <johannes@sipsolutions.net>
  Date:   Tue Feb 10 21:25:53 2009 +0100

    mac80211: RX aggregation: clean up stop session

and other parts were already present in the original

  commit d92684e66091c0f0101819619b315b4bb8b5bcc5
  Author: Ron Rindjunsky <ron.rindjunsky@intel.com>
  Date:   Mon Jan 28 14:07:22 2008 +0200

      mac80211: A-MPDU Tx add delBA from recipient support

The first problem is that I moved a BUG_ON before various
checks -- thereby making it possible to hit. As the comment
indicates, the BUG_ON can be removed since the ampdu_action
callback must already exist when the state is != IDLE.

The second problem isn't easily exploitable but there's a
race condition due to unconditionally setting the state to
OPERATIONAL when a delBA frame is received, even when no
aggregation session was ever initiated. All the drivers
accept stopping the session even then, but that opens a
race window where crashes could happen before the driver
accepts it. Right now, a WARN_ON may happen with non-HT
drivers, while the race opens only for HT drivers.

For this case, there are two things necessary to fix it:
 1) don't process spurious delBA frames, and be more careful
    about the session state; don't drop the lock

 2) HT drivers need to be prepared to handle a session stop
    even before the session was really started -- this is
    true for all drivers (that support aggregation) but
    iwlwifi which can be fixed easily. The other HT drivers
    (ath9k and ar9170) are behaving properly already.

Reported-by: Lennert Buytenhek <buytenh@marvell.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 12 insertions, 13 deletions

diff --git a/net/mac80211/agg-tx.c b/net/mac80211/agg-tx.c
index 8b4ac7659f0..b9005e1be8c 100644
--- a/net/mac80211/agg-tx.c
+++ b/net/mac80211/agg-tx.c
@@ -123,13 +123,18 @@ void ieee80211_send_bar(struct ieee80211_sub_if_data *sdata, u8 *ra, u16 tid, u1
 	ieee80211_tx_skb(sdata, skb, 0);
 }
 
-static int ___ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
-					   enum ieee80211_back_parties initiator)
+int ___ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
+				    enum ieee80211_back_parties initiator)
 {
 	struct ieee80211_local *local = sta->local;
 	int ret;
 	u8 *state;
 
+#ifdef CONFIG_MAC80211_HT_DEBUG
+	printk(KERN_DEBUG "Tx BA session stop requested for %pM tid %u\n",
+	       sta->sta.addr, tid);
+#endif /* CONFIG_MAC80211_HT_DEBUG */
+
 	state = &sta->ampdu_mlme.tid_state_tx[tid];
 
 	if (*state == HT_AGG_STATE_OPERATIONAL)
@@ -143,7 +148,6 @@ static int ___ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
 
 	/* HW shall not deny going back to legacy */
 	if (WARN_ON(ret)) {
-		*state = HT_AGG_STATE_OPERATIONAL;
 		/*
 		 * We may have pending packets get stuck in this case...
 		 * Not bothering with a workaround for now.
@@ -526,11 +530,6 @@ int __ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
 		goto unlock;
 	}
 
-#ifdef CONFIG_MAC80211_HT_DEBUG
-	printk(KERN_DEBUG "Tx BA session stop requested for %pM tid %u\n",
-	       sta->sta.addr, tid);
-#endif /* CONFIG_MAC80211_HT_DEBUG */
-
 	ret = ___ieee80211_stop_tx_ba_session(sta, tid, initiator);
 
  unlock:
diff --git a/net/mac80211/ht.c b/net/mac80211/ht.c
index 0891bfb0699..a6b8eb418ef 100644
--- a/net/mac80211/ht.c
+++ b/net/mac80211/ht.c
@@ -141,7 +141,6 @@ void ieee80211_process_delba(struct ieee80211_sub_if_data *sdata,
 			     struct sta_info *sta,
 			     struct ieee80211_mgmt *mgmt, size_t len)
 {
-	struct ieee80211_local *local = sdata->local;
 	u16 tid, params;
 	u16 initiator;
 
@@ -161,10 +160,9 @@ void ieee80211_process_delba(struct ieee80211_sub_if_data *sdata,
 						 WLAN_BACK_INITIATOR, 0);
 	else { /* WLAN_BACK_RECIPIENT */
 		spin_lock_bh(&sta->lock);
-		sta->ampdu_mlme.tid_state_tx[tid] =
-				HT_AGG_STATE_OPERATIONAL;
+		if (sta->ampdu_mlme.tid_state_tx[tid] & HT_ADDBA_REQUESTED_MSK)
+			___ieee80211_stop_tx_ba_session(sta, tid,
+							WLAN_BACK_RECIPIENT);
 		spin_unlock_bh(&sta->lock);
-		ieee80211_stop_tx_ba_session(&local->hw, sta->sta.addr, tid,
-					     WLAN_BACK_RECIPIENT);
 	}
 }
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 68eb5052179..33a7e75e838 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1057,6 +1057,8 @@ void ieee80211_process_addba_request(struct ieee80211_local *local,
 
 int __ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
 				   enum ieee80211_back_parties initiator);
+int ___ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
+				    enum ieee80211_back_parties initiator);
 
 /* Spectrum management */
 void ieee80211_process_measurement_req(struct ieee80211_sub_if_data *sdata,