iwlwifi: mvm: fix potential SKB leak on TXQ TX

When we transmit after TXQ dequeue, we aren't paying attention to
the return value of the transmit functions, leading to a potential
SKB leak.

Refactor the code a bit (and rename ..._tx to ..._tx_sta) to check
for this happening.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Fixes: cfbc6c4c ("iwlwifi: mvm: support mac80211 TXQs model")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c

@@ -755,6 +755,20 @@ int iwl_mvm_mac_setup_register(struct iwl_mvm *mvm)
 	return ret;
 }
 
+static void iwl_mvm_tx_skb(struct iwl_mvm *mvm, struct sk_buff *skb,
+			   struct ieee80211_sta *sta)
+{
+	if (likely(sta)) {
+		if (likely(iwl_mvm_tx_skb_sta(mvm, skb, sta) == 0))
+			return;
+	} else {
+		if (likely(iwl_mvm_tx_skb_non_sta(mvm, skb) == 0))
+			return;
+	}
+
+	ieee80211_free_txskb(mvm->hw, skb);
+}
+
 static void iwl_mvm_mac_tx(struct ieee80211_hw *hw,
 			   struct ieee80211_tx_control *control,
 			   struct sk_buff *skb)
@@ -798,14 +812,7 @@ static void iwl_mvm_mac_tx(struct ieee80211_hw *hw,
 		}
 	}
 
-	if (sta) {
-		if (iwl_mvm_tx_skb(mvm, skb, sta))
-			goto drop;
-		return;
-	}
-
-	if (iwl_mvm_tx_skb_non_sta(mvm, skb))
-		goto drop;
+	iwl_mvm_tx_skb(mvm, skb, sta);
 	return;
  drop:
 	ieee80211_free_txskb(hw, skb);
@@ -855,10 +862,7 @@ void iwl_mvm_mac_itxq_xmit(struct ieee80211_hw *hw, struct ieee80211_txq *txq)
 				break;
 			}
 
-			if (!txq->sta)
-				iwl_mvm_tx_skb_non_sta(mvm, skb);
-			else
-				iwl_mvm_tx_skb(mvm, skb, txq->sta);
+			iwl_mvm_tx_skb(mvm, skb, txq->sta);
 		}
 	} while (atomic_dec_return(&mvmtxq->tx_request));
 	rcu_read_unlock();

drivers/net/wireless/intel/iwlwifi/mvm/mvm.h

@@ -1508,8 +1508,8 @@ int __must_check iwl_mvm_send_cmd_status(struct iwl_mvm *mvm,
 int __must_check iwl_mvm_send_cmd_pdu_status(struct iwl_mvm *mvm, u32 id,
 					     u16 len, const void *data,
 					     u32 *status);
-int iwl_mvm_tx_skb(struct iwl_mvm *mvm, struct sk_buff *skb,
-		   struct ieee80211_sta *sta);
+int iwl_mvm_tx_skb_sta(struct iwl_mvm *mvm, struct sk_buff *skb,
+		       struct ieee80211_sta *sta);
 int iwl_mvm_tx_skb_non_sta(struct iwl_mvm *mvm, struct sk_buff *skb);
 void iwl_mvm_set_tx_cmd(struct iwl_mvm *mvm, struct sk_buff *skb,
 			struct iwl_tx_cmd *tx_cmd,

drivers/net/wireless/intel/iwlwifi/mvm/tx.c

@@ -1201,8 +1201,8 @@ static int iwl_mvm_tx_mpdu(struct iwl_mvm *mvm, struct sk_buff *skb,
 	return -1;
 }
 
-int iwl_mvm_tx_skb(struct iwl_mvm *mvm, struct sk_buff *skb,
-		   struct ieee80211_sta *sta)
+int iwl_mvm_tx_skb_sta(struct iwl_mvm *mvm, struct sk_buff *skb,
+		       struct ieee80211_sta *sta)
 {
 	struct iwl_mvm_sta *mvmsta = iwl_mvm_sta_from_mac80211(sta);
 	struct ieee80211_tx_info info;