wifi: rtw89: avoid possible TX wait initialization race

[ Upstream commit c24248e ]

The value of skb_data->wait indicates whether skb is passed on to the
core mac80211 stack or released by the driver itself.  Make sure that by
the time skb is added to txwd queue and becomes visible to the completing
side, it has already allocated and initialized TX wait related data (in
case it's needed).

This is found by code review and addresses a possible race scenario
described below:

      Waiting thread                          Completing thread

rtw89_core_send_nullfunc()
  rtw89_core_tx_write_link()
    ...
    rtw89_pci_txwd_submit()
      skb_data->wait = NULL
      /* add skb to the queue */
      skb_queue_tail(&txwd->queue, skb)

  /* another thread (e.g. rtw89_ops_tx) performs TX kick off for the same queue */

                                            rtw89_pci_napi_poll()
                                            ...
                                              rtw89_pci_release_txwd_skb()
                                                /* get skb from the queue */
                                                skb_unlink(skb, &txwd->queue)
                                                rtw89_pci_tx_status()
                                                  rtw89_core_tx_wait_complete()
                                                  /* use incorrect skb_data->wait */
  rtw89_core_tx_kick_off_and_wait()
  /* assign skb_data->wait but too late */

Found by Linux Verification Center (linuxtesting.org).

Fixes: 1ae5ca6 ("wifi: rtw89: add function to wait for completion of TX skbs")
Cc: [email protected]
Signed-off-by: Fedor Pchelkin <[email protected]>
Acked-by: Ping-Ke Shih <[email protected]>
Signed-off-by: Ping-Ke Shih <[email protected]>
Link: https://patch.msgid.link/[email protected]
[ adapted rtw89_core_tx_write_link() modifications to rtw89_core_tx_write() ]
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: pchelkin91

drivers/net/wireless/realtek/rtw89/core.c

@@ -978,25 +978,14 @@ void rtw89_core_tx_kick_off(struct rtw89_dev *rtwdev, u8 qsel)
 }
 
 int rtw89_core_tx_kick_off_and_wait(struct rtw89_dev *rtwdev, struct sk_buff *skb,
-				    int qsel, unsigned int timeout)
+				    struct rtw89_tx_wait_info *wait, int qsel,
+				    unsigned int timeout)
 {
-	struct rtw89_tx_skb_data *skb_data = RTW89_TX_SKB_CB(skb);
-	struct rtw89_tx_wait_info *wait;
 	unsigned long time_left;
 	int ret = 0;
 
 	lockdep_assert_wiphy(rtwdev->hw->wiphy);
 
-	wait = kzalloc(sizeof(*wait), GFP_KERNEL);
-	if (!wait) {
-		rtw89_core_tx_kick_off(rtwdev, qsel);
-		return 0;
-	}
-
-	init_completion(&wait->completion);
-	wait->skb = skb;
-	rcu_assign_pointer(skb_data->wait, wait);
-
 	rtw89_core_tx_kick_off(rtwdev, qsel);
 	time_left = wait_for_completion_timeout(&wait->completion,
 						msecs_to_jiffies(timeout));
@@ -1057,10 +1046,12 @@ int rtw89_h2c_tx(struct rtw89_dev *rtwdev,
 }
 
 int rtw89_core_tx_write(struct rtw89_dev *rtwdev, struct ieee80211_vif *vif,
-			struct ieee80211_sta *sta, struct sk_buff *skb, int *qsel)
+			struct ieee80211_sta *sta, struct sk_buff *skb, int *qsel,
+			struct rtw89_tx_wait_info *wait)
 {
 	struct rtw89_sta *rtwsta = sta_to_rtwsta_safe(sta);
 	struct rtw89_vif *rtwvif = vif_to_rtwvif(vif);
+	struct rtw89_tx_skb_data *skb_data = RTW89_TX_SKB_CB(skb);
 	struct rtw89_core_tx_request tx_req = {0};
 	struct rtw89_sta_link *rtwsta_link = NULL;
 	struct rtw89_vif_link *rtwvif_link;
@@ -1093,6 +1084,8 @@ int rtw89_core_tx_write(struct rtw89_dev *rtwdev, struct ieee80211_vif *vif,
 	rtw89_core_tx_update_desc_info(rtwdev, &tx_req);
 	rtw89_core_tx_wake(rtwdev, &tx_req);
 
+	rcu_assign_pointer(skb_data->wait, wait);
+
 	ret = rtw89_hci_tx_write(rtwdev, &tx_req);
 	if (ret) {
 		rtw89_err(rtwdev, "failed to transmit skb to HCI\n");
@@ -2908,7 +2901,7 @@ static void rtw89_core_txq_push(struct rtw89_dev *rtwdev,
 			goto out;
 		}
 		rtw89_core_txq_check_agg(rtwdev, rtwtxq, skb);
-		ret = rtw89_core_tx_write(rtwdev, vif, sta, skb, NULL);
+		ret = rtw89_core_tx_write(rtwdev, vif, sta, skb, NULL, NULL);
 		if (ret) {
 			rtw89_err(rtwdev, "failed to push txq: %d\n", ret);
 			ieee80211_free_txskb(rtwdev->hw, skb);
@@ -3084,7 +3077,7 @@ static void rtw89_core_sta_pending_tx_iter(void *data,
 	skb_queue_walk_safe(&rtwsta->roc_queue, skb, tmp) {
 		skb_unlink(skb, &rtwsta->roc_queue);
 
-		ret = rtw89_core_tx_write(rtwdev, vif, sta, skb, &qsel);
+		ret = rtw89_core_tx_write(rtwdev, vif, sta, skb, &qsel, NULL);
 		if (ret) {
 			rtw89_warn(rtwdev, "pending tx failed with %d\n", ret);
 			dev_kfree_skb_any(skb);
@@ -3106,6 +3099,7 @@ static int rtw89_core_send_nullfunc(struct rtw89_dev *rtwdev,
 				    struct rtw89_vif_link *rtwvif_link, bool qos, bool ps)
 {
 	struct ieee80211_vif *vif = rtwvif_link_to_vif(rtwvif_link);
+	struct rtw89_tx_wait_info *wait;
 	struct ieee80211_sta *sta;
 	struct ieee80211_hdr *hdr;
 	struct sk_buff *skb;
@@ -3114,6 +3108,12 @@ static int rtw89_core_send_nullfunc(struct rtw89_dev *rtwdev,
 	if (vif->type != NL80211_IFTYPE_STATION || !vif->cfg.assoc)
 		return 0;
 
+	wait = kzalloc(sizeof(*wait), GFP_KERNEL);
+	if (!wait)
+		return -ENOMEM;
+
+	init_completion(&wait->completion);
+
 	rcu_read_lock();
 	sta = ieee80211_find_sta(vif, vif->cfg.ap_addr);
 	if (!sta) {
@@ -3127,11 +3127,13 @@ static int rtw89_core_send_nullfunc(struct rtw89_dev *rtwdev,
 		goto out;
 	}
 
+	wait->skb = skb;
+
 	hdr = (struct ieee80211_hdr *)skb->data;
 	if (ps)
 		hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PM);
 
-	ret = rtw89_core_tx_write(rtwdev, vif, sta, skb, &qsel);
+	ret = rtw89_core_tx_write(rtwdev, vif, sta, skb, &qsel, wait);
 	if (ret) {
 		rtw89_warn(rtwdev, "nullfunc transmit failed: %d\n", ret);
 		dev_kfree_skb_any(skb);
@@ -3140,10 +3142,11 @@ static int rtw89_core_send_nullfunc(struct rtw89_dev *rtwdev,
 
 	rcu_read_unlock();
 
-	return rtw89_core_tx_kick_off_and_wait(rtwdev, skb, qsel,
+	return rtw89_core_tx_kick_off_and_wait(rtwdev, skb, wait, qsel,
 					       RTW89_ROC_TX_TIMEOUT);
 out:
 	rcu_read_unlock();
+	kfree(wait);
 
 	return ret;
 }

drivers/net/wireless/realtek/rtw89/core.h

@@ -6818,12 +6818,14 @@ static inline bool rtw89_is_rtl885xb(struct rtw89_dev *rtwdev)
 }
 
 int rtw89_core_tx_write(struct rtw89_dev *rtwdev, struct ieee80211_vif *vif,
-			struct ieee80211_sta *sta, struct sk_buff *skb, int *qsel);
+			struct ieee80211_sta *sta, struct sk_buff *skb, int *qsel,
+			struct rtw89_tx_wait_info *wait);
 int rtw89_h2c_tx(struct rtw89_dev *rtwdev,
 		 struct sk_buff *skb, bool fwdl);
 void rtw89_core_tx_kick_off(struct rtw89_dev *rtwdev, u8 qsel);
 int rtw89_core_tx_kick_off_and_wait(struct rtw89_dev *rtwdev, struct sk_buff *skb,
-				    int qsel, unsigned int timeout);
+				    struct rtw89_tx_wait_info *wait, int qsel,
+				    unsigned int timeout);
 void rtw89_core_fill_txdesc(struct rtw89_dev *rtwdev,
 			    struct rtw89_tx_desc_info *desc_info,
 			    void *txdesc);

drivers/net/wireless/realtek/rtw89/mac80211.c

@@ -36,7 +36,7 @@ static void rtw89_ops_tx(struct ieee80211_hw *hw,
 		return;
 	}
 
-	ret = rtw89_core_tx_write(rtwdev, vif, sta, skb, &qsel);
+	ret = rtw89_core_tx_write(rtwdev, vif, sta, skb, &qsel, NULL);
 	if (ret) {
 		rtw89_err(rtwdev, "failed to transmit skb: %d\n", ret);
 		ieee80211_free_txskb(hw, skb);

drivers/net/wireless/realtek/rtw89/pci.c

@@ -1366,7 +1366,6 @@ static int rtw89_pci_txwd_submit(struct rtw89_dev *rtwdev,
 	struct pci_dev *pdev = rtwpci->pdev;
 	struct sk_buff *skb = tx_req->skb;
 	struct rtw89_pci_tx_data *tx_data = RTW89_PCI_TX_SKB_CB(skb);
-	struct rtw89_tx_skb_data *skb_data = RTW89_TX_SKB_CB(skb);
 	bool en_wd_info = desc_info->en_wd_info;
 	u32 txwd_len;
 	u32 txwp_len;
@@ -1382,7 +1381,6 @@ static int rtw89_pci_txwd_submit(struct rtw89_dev *rtwdev,
 	}
 
 	tx_data->dma = dma;
-	rcu_assign_pointer(skb_data->wait, NULL);
 
 	txwp_len = sizeof(*txwp_info);
 	txwd_len = chip->txwd_body_size;