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mac80211: fix race in TX aggregation
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When disabling TX aggregation because it was rejected or from
the timer (it was not accepted), there is a window where we
first set the state to operation, unlock, and then undo the
whole thing. Avoid that by splitting up the stop function.
Also get rid of the pointless sta_info indirection in the timer.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
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Johannes Berg authored and John W. Linville committed Feb 13, 2009
1 parent 86ab6c5 commit 23e6a7e
Showing 1 changed file with 48 additions and 47 deletions.
95 changes: 48 additions & 47 deletions net/mac80211/agg-tx.c
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Original file line number Diff line number Diff line change
Expand Up @@ -123,6 +123,34 @@ 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 ieee80211_local *local,
struct sta_info *sta, u16 tid,
enum ieee80211_back_parties initiator)
{
int ret;
u8 *state;

state = &sta->ampdu_mlme.tid_state_tx[tid];

if (local->hw.ampdu_queues)
ieee80211_stop_queue(&local->hw, sta->tid_to_tx_q[tid]);

*state = HT_AGG_STATE_REQ_STOP_BA_MSK |
(initiator << HT_AGG_STATE_INITIATOR_SHIFT);

ret = local->ops->ampdu_action(&local->hw, IEEE80211_AMPDU_TX_STOP,
&sta->sta, tid, NULL);

/* HW shall not deny going back to legacy */
if (WARN_ON(ret)) {
*state = HT_AGG_STATE_OPERATIONAL;
if (local->hw.ampdu_queues)
ieee80211_wake_queue(&local->hw, sta->tid_to_tx_q[tid]);
}

return ret;
}

/*
* After sending add Block Ack request we activated a timer until
* add Block Ack response will arrive from the recipient.
Expand All @@ -135,23 +163,13 @@ static void sta_addba_resp_timer_expired(unsigned long data)
* flow in sta_info_create gives the TID as data, while the timer_to_id
* array gives the sta through container_of */
u16 tid = *(u8 *)data;
struct sta_info *temp_sta = container_of((void *)data,
struct sta_info *sta = container_of((void *)data,
struct sta_info, timer_to_tid[tid]);

struct ieee80211_local *local = temp_sta->local;
struct ieee80211_hw *hw = &local->hw;
struct sta_info *sta;
struct ieee80211_local *local = sta->local;
u8 *state;

rcu_read_lock();

sta = sta_info_get(local, temp_sta->sta.addr);
if (!sta) {
rcu_read_unlock();
return;
}

state = &sta->ampdu_mlme.tid_state_tx[tid];

/* check if the TID waits for addBA response */
spin_lock_bh(&sta->lock);
if (!(*state & HT_ADDBA_REQUESTED_MSK)) {
Expand All @@ -161,21 +179,15 @@ static void sta_addba_resp_timer_expired(unsigned long data)
printk(KERN_DEBUG "timer expired on tid %d but we are not "
"expecting addBA response there", tid);
#endif
goto timer_expired_exit;
return;
}

#ifdef CONFIG_MAC80211_HT_DEBUG
printk(KERN_DEBUG "addBA response timer expired on tid %d\n", tid);
#endif

/* go through the state check in stop_BA_session */
*state = HT_AGG_STATE_OPERATIONAL;
__ieee80211_stop_tx_ba_session(local, sta, tid, WLAN_BACK_INITIATOR);
spin_unlock_bh(&sta->lock);
ieee80211_stop_tx_ba_session(hw, temp_sta->sta.addr, tid,
WLAN_BACK_INITIATOR);

timer_expired_exit:
rcu_read_unlock();
}

int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
Expand All @@ -187,6 +199,9 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
u8 *state;
int ret = 0;

if (WARN_ON(!local->ops->ampdu_action))
return -EINVAL;

if ((tid >= STA_TID_NUM) || !(hw->flags & IEEE80211_HW_AMPDU_AGGREGATION))
return -EINVAL;

Expand Down Expand Up @@ -280,9 +295,8 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
/* This is slightly racy because the queue isn't stopped */
start_seq_num = sta->tid_seq[tid];

if (local->ops->ampdu_action)
ret = local->ops->ampdu_action(hw, IEEE80211_AMPDU_TX_START,
&sta->sta, tid, &start_seq_num);
ret = local->ops->ampdu_action(hw, IEEE80211_AMPDU_TX_START,
&sta->sta, tid, &start_seq_num);

if (ret) {
/* No need to requeue the packets in the agg queue, since we
Expand Down Expand Up @@ -423,6 +437,9 @@ int ieee80211_stop_tx_ba_session(struct ieee80211_hw *hw,
u8 *state;
int ret = 0;

if (WARN_ON(!local->ops->ampdu_action))
return -EINVAL;

if (tid >= STA_TID_NUM)
return -EINVAL;

Expand All @@ -439,35 +456,21 @@ int ieee80211_stop_tx_ba_session(struct ieee80211_hw *hw,

if (*state != HT_AGG_STATE_OPERATIONAL) {
ret = -ENOENT;
goto stop_BA_exit;
goto unlock;
}

#ifdef CONFIG_MAC80211_HT_DEBUG
printk(KERN_DEBUG "Tx BA session stop requested for %pM tid %u\n",
ra, tid);
#endif /* CONFIG_MAC80211_HT_DEBUG */

if (hw->ampdu_queues)
ieee80211_stop_queue(hw, sta->tid_to_tx_q[tid]);

*state = HT_AGG_STATE_REQ_STOP_BA_MSK |
(initiator << HT_AGG_STATE_INITIATOR_SHIFT);
ret = __ieee80211_stop_tx_ba_session(local, sta, tid, initiator);

if (local->ops->ampdu_action)
ret = local->ops->ampdu_action(hw, IEEE80211_AMPDU_TX_STOP,
&sta->sta, tid, NULL);

/* HW shall not deny going back to legacy */
if (WARN_ON(ret)) {
*state = HT_AGG_STATE_OPERATIONAL;
if (hw->ampdu_queues)
ieee80211_wake_queue(hw, sta->tid_to_tx_q[tid]);
goto stop_BA_exit;
}

stop_BA_exit:
unlock:
spin_unlock_bh(&sta->lock);

rcu_read_unlock();

return ret;
}
EXPORT_SYMBOL(ieee80211_stop_tx_ba_session);
Expand Down Expand Up @@ -623,10 +626,8 @@ void ieee80211_process_addba_resp(struct ieee80211_local *local,
spin_unlock_bh(&sta->lock);
} else {
sta->ampdu_mlme.addba_req_num[tid]++;
/* this will allow the state check in stop_BA_session */
*state = HT_AGG_STATE_OPERATIONAL;
__ieee80211_stop_tx_ba_session(local, sta, tid,
WLAN_BACK_INITIATOR);
spin_unlock_bh(&sta->lock);
ieee80211_stop_tx_ba_session(hw, sta->sta.addr, tid,
WLAN_BACK_INITIATOR);
}
}

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