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>

1 files changed, 17 insertions, 13 deletions

diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 97d4a537ca2f..f79f6b9938a6 100644
--- 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]);