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Subject[056/119] mac80211: fix spurious delBA handling
2.6.31-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Johannes Berg <johannes@sipsolutions.net>
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>

---
drivers/net/wireless/iwlwifi/iwl-tx.c | 10 +++++++++-
include/net/mac80211.h | 6 ++++++
net/mac80211/agg-tx.c | 15 +++++++--------
net/mac80211/ht.c | 8 +++-----
net/mac80211/ieee80211_i.h | 2 ++
5 files changed, 27 insertions(+), 14 deletions(-)
--- a/drivers/net/wireless/iwlwifi/iwl-tx.c
+++ b/drivers/net/wireless/iwlwifi/iwl-tx.c
@@ -1233,8 +1233,16 @@ int iwl_tx_agg_stop(struct iwl_priv *pri
return -ENXIO;
}

+ if (priv->stations[sta_id].tid[tid].agg.state ==
+ IWL_EMPTYING_HW_QUEUE_ADDBA) {
+ IWL_DEBUG_HT(priv, "AGG stop before setup done\n");
+ ieee80211_stop_tx_ba_cb_irqsafe(priv->hw, ra, tid);
+ priv->stations[sta_id].tid[tid].agg.state = IWL_AGG_OFF;
+ return 0;
+ }
+
if (priv->stations[sta_id].tid[tid].agg.state != IWL_AGG_ON)
- IWL_WARN(priv, "Stopping AGG while state not IWL_AGG_ON\n");
+ IWL_WARN(priv, "Stopping AGG while state not ON or starting\n");

tid_data = &priv->stations[sta_id].tid[tid];
ssn = (tid_data->seq_number & IEEE80211_SCTL_SEQ) >> 4;
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -1244,6 +1244,12 @@ enum ieee80211_filter_flags {
*
* These flags are used with the ampdu_action() callback in
* &struct ieee80211_ops to indicate which action is needed.
+ *
+ * Note that drivers MUST be able to deal with a TX aggregation
+ * session being stopped even before they OK'ed starting it by
+ * calling ieee80211_start_tx_ba_cb(_irqsafe), because the peer
+ * might receive the addBA frame and send a delBA right away!
+ *
* @IEEE80211_AMPDU_RX_START: start Rx aggregation
* @IEEE80211_AMPDU_RX_STOP: stop Rx aggregation
* @IEEE80211_AMPDU_TX_START: start Tx aggregation
--- a/net/mac80211/agg-tx.c
+++ b/net/mac80211/agg-tx.c
@@ -123,13 +123,18 @@ void ieee80211_send_bar(struct ieee80211
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_sessi

/* 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(struc
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:
--- a/net/mac80211/ht.c
+++ b/net/mac80211/ht.c
@@ -141,7 +141,6 @@ void ieee80211_process_delba(struct ieee
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 ieee
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);
}
}
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1057,6 +1057,8 @@ void ieee80211_process_addba_request(str

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,



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