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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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