wifi: rtw89: avoid possible TX wait initialization race

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: 1ae5ca615285 ("wifi: rtw89: add function to wait for completion of TX skbs")
Cc: stable@vger.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250919210852.823912-3-pchelkin@ispras.ru

diff --git a/drivers/net/wireless/realtek/rtw89/core.c b/drivers/net/wireless/realtek/rtw89/core.c
index ec467ae0e9e6edff7b6774ce078a81c3d90e1498..1f44c7fc1c5e9fb79367408603d8ed225f9afec0 100644 (file)
--- a/drivers/net/wireless/realtek/rtw89/core.c
+++ b/drivers/net/wireless/realtek/rtw89/core.c
@@ -1153,25 +1153,14 @@ 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));
@@ -1234,10 +1223,12 @@ int rtw89_h2c_tx(struct rtw89_dev *rtwdev,
 static int rtw89_core_tx_write_link(struct rtw89_dev *rtwdev,
                                    struct rtw89_vif_link *rtwvif_link,
                                    struct rtw89_sta_link *rtwsta_link,
-                                   struct sk_buff *skb, int *qsel, bool sw_mld)
+                                   struct sk_buff *skb, int *qsel, bool sw_mld,
+                                   struct rtw89_tx_wait_info *wait)
 {
        struct ieee80211_sta *sta = rtwsta_link_to_sta_safe(rtwsta_link);
        struct ieee80211_vif *vif = rtwvif_link_to_vif(rtwvif_link);
+       struct rtw89_tx_skb_data *skb_data = RTW89_TX_SKB_CB(skb);
        struct rtw89_vif *rtwvif = rtwvif_link->rtwvif;
        struct rtw89_core_tx_request tx_req = {};
        int ret;
@@ -1254,6 +1245,8 @@ static int rtw89_core_tx_write_link(struct rtw89_dev *rtwdev,
        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");
@@ -1290,7 +1283,8 @@ int rtw89_core_tx_write(struct rtw89_dev *rtwdev, struct ieee80211_vif *vif,
                }
        }
 
-       return rtw89_core_tx_write_link(rtwdev, rtwvif_link, rtwsta_link, skb, qsel, false);
+       return rtw89_core_tx_write_link(rtwdev, rtwvif_link, rtwsta_link, skb, qsel, false,
+                                       NULL);
 }
 
 static __le32 rtw89_build_txwd_body0(struct rtw89_tx_desc_info *desc_info)
@@ -3928,6 +3922,7 @@ int rtw89_core_send_nullfunc(struct rtw89_dev *rtwdev, struct rtw89_vif_link *rt
        struct ieee80211_vif *vif = rtwvif_link_to_vif(rtwvif_link);
        int link_id = ieee80211_vif_is_mld(vif) ? rtwvif_link->link_id : -1;
        struct rtw89_sta_link *rtwsta_link;
+       struct rtw89_tx_wait_info *wait;
        struct ieee80211_sta *sta;
        struct ieee80211_hdr *hdr;
        struct rtw89_sta *rtwsta;
@@ -3937,6 +3932,12 @@ int rtw89_core_send_nullfunc(struct rtw89_dev *rtwdev, struct rtw89_vif_link *rt
        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) {
@@ -3951,6 +3952,8 @@ int rtw89_core_send_nullfunc(struct rtw89_dev *rtwdev, struct rtw89_vif_link *rt
                goto out;
        }
 
+       wait->skb = skb;
+
        hdr = (struct ieee80211_hdr *)skb->data;
        if (ps)
                hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PM);
@@ -3961,7 +3964,8 @@ int rtw89_core_send_nullfunc(struct rtw89_dev *rtwdev, struct rtw89_vif_link *rt
                goto out;
        }
 
-       ret = rtw89_core_tx_write_link(rtwdev, rtwvif_link, rtwsta_link, skb, &qsel, true);
+       ret = rtw89_core_tx_write_link(rtwdev, rtwvif_link, rtwsta_link, skb, &qsel, true,
+                                      wait);
        if (ret) {
                rtw89_warn(rtwdev, "nullfunc transmit failed: %d\n", ret);
                dev_kfree_skb_any(skb);
@@ -3970,10 +3974,11 @@ int rtw89_core_send_nullfunc(struct rtw89_dev *rtwdev, struct rtw89_vif_link *rt
 
        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,
                                               timeout);
 out:
        rcu_read_unlock();
+       kfree(wait);
 
        return ret;
 }

diff --git a/drivers/net/wireless/realtek/rtw89/core.h b/drivers/net/wireless/realtek/rtw89/core.h
index d15fa70eb4dc7b9f415a6da5441c37041e0d089d..928c8c84c9644b5569036ba7818e2170dde63db7 100644 (file)
--- a/drivers/net/wireless/realtek/rtw89/core.h
+++ b/drivers/net/wireless/realtek/rtw89/core.h
@@ -7476,7 +7476,8 @@ 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);

diff --git a/drivers/net/wireless/realtek/rtw89/pci.c b/drivers/net/wireless/realtek/rtw89/pci.c
index 8dd91d867ea6ebc3656a8cb592e6405d72a55de6..0ee5f8579447642129090c8d1a6add95510e9b89 100644 (file)
--- a/drivers/net/wireless/realtek/rtw89/pci.c
+++ b/drivers/net/wireless/realtek/rtw89/pci.c
@@ -1494,7 +1494,6 @@ 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;
@@ -1510,7 +1509,6 @@ 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;