mac80211: fix purging multicast PS buffer queue

The code currently assumes that buffered multicast PS frames don't have
a pending ACK frame for tx status reporting.
However, hostapd sends a broadcast deauth frame on teardown for which tx
status is requested. This can lead to the "Have pending ack frames"
warning on module reload.
Fix this by using ieee80211_free_txskb/ieee80211_purge_tx_queue.

Cc: stable@vger.kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/cfg.c

@@ -869,7 +869,7 @@ static int ieee80211_stop_ap(struct wiphy *wiphy, struct net_device *dev)
 
 	/* free all potentially still buffered bcast frames */
 	local->total_ps_buffered -= skb_queue_len(&sdata->u.ap.ps.bc_buf);
-	skb_queue_purge(&sdata->u.ap.ps.bc_buf);
+	ieee80211_purge_tx_queue(&local->hw, &sdata->u.ap.ps.bc_buf);
 
 	mutex_lock(&local->mtx);
 	ieee80211_vif_copy_chanctx_to_vlans(sdata, true);

net/mac80211/tx.c

@@ -368,7 +368,7 @@ static void purge_old_ps_buffers(struct ieee80211_local *local)
 		skb = skb_dequeue(&ps->bc_buf);
 		if (skb) {
 			purged++;
-			dev_kfree_skb(skb);
+			ieee80211_free_txskb(&local->hw, skb);
 		}
 		total += skb_queue_len(&ps->bc_buf);
 	}
@@ -451,7 +451,7 @@ ieee80211_tx_h_multicast_ps_buf(struct ieee80211_tx_data *tx)
 	if (skb_queue_len(&ps->bc_buf) >= AP_MAX_BC_BUFFER) {
 		ps_dbg(tx->sdata,
 		       "BC TX buffer full - dropping the oldest frame\n");
-		dev_kfree_skb(skb_dequeue(&ps->bc_buf));
+		ieee80211_free_txskb(&tx->local->hw, skb_dequeue(&ps->bc_buf));
 	} else
 		tx->local->total_ps_buffered++;
 
@@ -4275,7 +4275,7 @@ ieee80211_get_buffered_bc(struct ieee80211_hw *hw,
 			sdata = IEEE80211_DEV_TO_SUB_IF(skb->dev);
 		if (!ieee80211_tx_prepare(sdata, &tx, NULL, skb))
 			break;
-		dev_kfree_skb_any(skb);
+		ieee80211_free_txskb(hw, skb);
 	}
 
 	info = IEEE80211_SKB_CB(skb);