mac80211: fix ieee80211_get_buffered_bc

fix bss not initialized in ieee80211_get_buffered_bc
and unbalanced locking

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/tx.c

@@ -1947,7 +1947,7 @@ ieee80211_get_buffered_bc(struct ieee80211_hw *hw,
 			  struct ieee80211_vif *vif)
 {
 	struct ieee80211_local *local = hw_to_local(hw);
-	struct sk_buff *skb;
+	struct sk_buff *skb = NULL;
 	struct sta_info *sta;
 	ieee80211_tx_handler *handler;
 	struct ieee80211_tx_data tx;
@@ -1960,27 +1960,24 @@ ieee80211_get_buffered_bc(struct ieee80211_hw *hw,
 
 	sdata = vif_to_sdata(vif);
 	bdev = sdata->dev;
-
+	bss = &sdata->u.ap;
 
 	if (!bss)
 		return NULL;
 
 	rcu_read_lock();
 	beacon = rcu_dereference(bss->beacon);
 
-	if (sdata->vif.type != IEEE80211_IF_TYPE_AP || !beacon ||
-	    !beacon->head) {
-		rcu_read_unlock();
-		return NULL;
-	}
+	if (sdata->vif.type != IEEE80211_IF_TYPE_AP || !beacon || !beacon->head)
+		goto out;
 
 	if (bss->dtim_count != 0)
-		return NULL; /* send buffered bc/mc only after DTIM beacon */
+		goto out; /* send buffered bc/mc only after DTIM beacon */
 
 	while (1) {
 		skb = skb_dequeue(&bss->ps_bc_buf);
 		if (!skb)
-			return NULL;
+			goto out;
 		local->total_ps_buffered--;
 
 		if (!skb_queue_empty(&bss->ps_bc_buf) && skb->len >= 2) {
@@ -2023,6 +2020,7 @@ ieee80211_get_buffered_bc(struct ieee80211_hw *hw,
 		skb = NULL;
 	}
 
+out:
 	rcu_read_unlock();
 
 	return skb;