mac80211: fix deadlock in sta->lock

This patch fixes a deadlock of sta->lock use, occurring while changing
tx aggregation states, as dev_queue_xmit end up in new function
test_and_clear_sta_flags that uses that lock thus leading to deadlock

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Ron Rindjunsky <ron.rindjunsky@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 97d4a53..f79f6b9 100644 (file)
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -589,8 +589,8 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
        sta = sta_info_get(local, ra);
        if (!sta) {
                printk(KERN_DEBUG "Could not find the station\n");
-               rcu_read_unlock();
-               return -ENOENT;
+               ret = -ENOENT;
+               goto exit;
        }
 
        spin_lock_bh(&sta->lock);
@@ -598,7 +598,7 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
        /* we have tried too many times, receiver does not want A-MPDU */
        if (sta->ampdu_mlme.addba_req_num[tid] > HT_AGG_MAX_RETRIES) {
                ret = -EBUSY;
-               goto start_ba_exit;
+               goto err_unlock_sta;
        }
 
        state = &sta->ampdu_mlme.tid_state_tx[tid];
@@ -609,7 +609,7 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
                                 "idle on tid %u\n", tid);
 #endif /* CONFIG_MAC80211_HT_DEBUG */
                ret = -EAGAIN;
-               goto start_ba_exit;
+               goto err_unlock_sta;
        }
 
        /* prepare A-MPDU MLME for Tx aggregation */
@@ -620,7 +620,7 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
                        printk(KERN_ERR "allocate tx mlme to tid %d failed\n",
                                        tid);
                ret = -ENOMEM;
-               goto start_ba_exit;
+               goto err_unlock_sta;
        }
        /* Tx timer */
        sta->ampdu_mlme.tid_tx[tid]->addba_resp_timer.function =
@@ -643,7 +643,7 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
                printk(KERN_DEBUG "BA request denied - queue unavailable for"
                                        " tid %d\n", tid);
 #endif /* CONFIG_MAC80211_HT_DEBUG */
-               goto start_ba_err;
+               goto err_unlock_queue;
        }
        sdata = sta->sdata;
 
@@ -665,12 +665,13 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
                                        " tid %d\n", tid);
 #endif /* CONFIG_MAC80211_HT_DEBUG */
                *state = HT_AGG_STATE_IDLE;
-               goto start_ba_err;
+               goto err_unlock_queue;
        }
 
        /* Will put all the packets in the new SW queue */
        ieee80211_requeue(local, ieee802_1d_to_ac[tid]);
        spin_unlock_bh(&local->mdev->queue_lock);
+       spin_unlock_bh(&sta->lock);
 
        /* send an addBA request */
        sta->ampdu_mlme.dialog_token_allocator++;
@@ -678,25 +679,26 @@ int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
                        sta->ampdu_mlme.dialog_token_allocator;
        sta->ampdu_mlme.tid_tx[tid]->ssn = start_seq_num;
 
+
        ieee80211_send_addba_request(sta->sdata->dev, ra, tid,
                         sta->ampdu_mlme.tid_tx[tid]->dialog_token,
                         sta->ampdu_mlme.tid_tx[tid]->ssn,
                         0x40, 5000);
-
        /* activate the timer for the recipient's addBA response */
        sta->ampdu_mlme.tid_tx[tid]->addba_resp_timer.expires =
                                jiffies + ADDBA_RESP_INTERVAL;
        add_timer(&sta->ampdu_mlme.tid_tx[tid]->addba_resp_timer);
        printk(KERN_DEBUG "activated addBA response timer on tid %d\n", tid);
-       goto start_ba_exit;
+       goto exit;
 
-start_ba_err:
+err_unlock_queue:
        kfree(sta->ampdu_mlme.tid_tx[tid]);
        sta->ampdu_mlme.tid_tx[tid] = NULL;
        spin_unlock_bh(&local->mdev->queue_lock);
        ret = -EBUSY;
-start_ba_exit:
+err_unlock_sta:
        spin_unlock_bh(&sta->lock);
+exit:
        rcu_read_unlock();
        return ret;
 }
@@ -835,10 +837,11 @@ void ieee80211_stop_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u8 tid)
        }
        state = &sta->ampdu_mlme.tid_state_tx[tid];
 
-       spin_lock_bh(&sta->lock);
+       /* NOTE: no need to use sta->lock in this state check, as
+        * ieee80211_stop_tx_ba_session will let only
+        * one stop call to pass through per sta/tid */
        if ((*state & HT_AGG_STATE_REQ_STOP_BA_MSK) == 0) {
                printk(KERN_DEBUG "unexpected callback to A-MPDU stop\n");
-               spin_unlock_bh(&sta->lock);
                rcu_read_unlock();
                return;
        }
@@ -861,6 +864,7 @@ void ieee80211_stop_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u8 tid)
         * ieee80211_wake_queue is not used here as this queue is not
         * necessarily stopped */
        netif_schedule(local->mdev);
+       spin_lock_bh(&sta->lock);
        *state = HT_AGG_STATE_IDLE;
        sta->ampdu_mlme.addba_req_num[tid] = 0;
        kfree(sta->ampdu_mlme.tid_tx[tid]);