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FAILED: patch "[PATCH] wifi: rtw89: fix use-after-free in" failed to apply to 6.16-stable tree

PATCH New [email protected] 2 participants 3 messages Oct 3, 2025

Subsystems (2)
Stable branch Realtek wireless driver (rtw89)
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author maintainer
#0 lore raw

The patch below does not apply to the 6.16-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.16.y
git checkout FETCH_HEAD
git cherry-pick -x 3e31a6bc07312b448fad3b45de578471f86f0e77
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025100340-dwelling-engross-0738@gregkh' --subject-prefix 'PATCH 6.16.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3e31a6bc07312b448fad3b45de578471f86f0e77 Mon Sep 17 00:00:00 2001
From: Fedor Pchelkin <[email protected]>
Date: Sat, 20 Sep 2025 00:08:47 +0300
Subject: [PATCH] wifi: rtw89: fix use-after-free in
rtw89_core_tx_kick_off_and_wait()

There is a bug observed when rtw89_core_tx_kick_off_and_wait() tries to access already freed skb_data:

 BUG: KFENCE: use-after-free write in rtw89_core_tx_kick_off_and_wait drivers/net/wireless/realtek/rtw89/core.c:1110

 CPU: 6 UID: 0 PID: 41377 Comm: kworker/u64:24 Not tainted  6.17.0-rc1+ #1 PREEMPT(lazy)
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS edk2-20250523-14.fc42 05/23/2025
 Workqueue: events_unbound cfg80211_wiphy_work [cfg80211]

Use-after-free write at 0x0000000020309d9d (in kfence-#251):

 rtw89_core_tx_kick_off_and_wait drivers/net/wireless/realtek/rtw89/core.c:1110
 rtw89_core_scan_complete drivers/net/wireless/realtek/rtw89/core.c:5338
 rtw89_hw_scan_complete_cb drivers/net/wireless/realtek/rtw89/fw.c:7979
 rtw89_chanctx_proceed_cb drivers/net/wireless/realtek/rtw89/chan.c:3165
 rtw89_chanctx_proceed drivers/net/wireless/realtek/rtw89/chan.h:141
 rtw89_hw_scan_complete drivers/net/wireless/realtek/rtw89/fw.c:8012
 rtw89_mac_c2h_scanofld_rsp drivers/net/wireless/realtek/rtw89/mac.c:5059
 rtw89_fw_c2h_work drivers/net/wireless/realtek/rtw89/fw.c:6758
 process_one_work kernel/workqueue.c:3241
 worker_thread kernel/workqueue.c:3400
 kthread kernel/kthread.c:463
 ret_from_fork arch/x86/kernel/process.c:154
 ret_from_fork_asm arch/x86/entry/entry_64.S:258

kfence-#251: 0x0000000056e2393d-0x000000009943cb62, size=232, cache=skbuff_head_cache

allocated by task 41377 on cpu 6 at 77869.159548s (0.009551s ago):

 __alloc_skb net/core/skbuff.c:659
 __netdev_alloc_skb net/core/skbuff.c:734
 ieee80211_nullfunc_get net/mac80211/tx.c:5844
 rtw89_core_send_nullfunc drivers/net/wireless/realtek/rtw89/core.c:3431
 rtw89_core_scan_complete drivers/net/wireless/realtek/rtw89/core.c:5338
 rtw89_hw_scan_complete_cb drivers/net/wireless/realtek/rtw89/fw.c:7979
 rtw89_chanctx_proceed_cb drivers/net/wireless/realtek/rtw89/chan.c:3165
 rtw89_chanctx_proceed drivers/net/wireless/realtek/rtw89/chan.c:3194
 rtw89_hw_scan_complete drivers/net/wireless/realtek/rtw89/fw.c:8012
 rtw89_mac_c2h_scanofld_rsp drivers/net/wireless/realtek/rtw89/mac.c:5059
 rtw89_fw_c2h_work drivers/net/wireless/realtek/rtw89/fw.c:6758
 process_one_work kernel/workqueue.c:3241
 worker_thread kernel/workqueue.c:3400
 kthread kernel/kthread.c:463
 ret_from_fork arch/x86/kernel/process.c:154
 ret_from_fork_asm arch/x86/entry/entry_64.S:258

freed by task 1045 on cpu 9 at 77869.168393s (0.001557s ago):

 ieee80211_tx_status_skb net/mac80211/status.c:1117
 rtw89_pci_release_txwd_skb drivers/net/wireless/realtek/rtw89/pci.c:564
 rtw89_pci_release_tx_skbs.isra.0 drivers/net/wireless/realtek/rtw89/pci.c:651
 rtw89_pci_release_tx drivers/net/wireless/realtek/rtw89/pci.c:676
 rtw89_pci_napi_poll drivers/net/wireless/realtek/rtw89/pci.c:4238
 __napi_poll net/core/dev.c:7495
 net_rx_action net/core/dev.c:7557 net/core/dev.c:7684
 handle_softirqs kernel/softirq.c:580
 do_softirq.part.0 kernel/softirq.c:480
 __local_bh_enable_ip kernel/softirq.c:407
 rtw89_pci_interrupt_threadfn drivers/net/wireless/realtek/rtw89/pci.c:927
 irq_thread_fn kernel/irq/manage.c:1133
 irq_thread kernel/irq/manage.c:1257
 kthread kernel/kthread.c:463
 ret_from_fork arch/x86/kernel/process.c:154
 ret_from_fork_asm arch/x86/entry/entry_64.S:258

It is a consequence of a race between the waiting and the signaling side of the completion:

Waiting thread Completing thread

rtw89_core_tx_kick_off_and_wait()
rcu_assign_pointer(skb_data->wait, wait)
/* start waiting */
wait_for_completion_timeout()

                                                rtw89_pci_tx_status()
                                                  rtw89_core_tx_wait_complete()
                                                    rcu_read_lock()
                                                    /* signals completion and
                                                     * proceeds further
                                                     */
                                                    complete(&wait->completion)
                                                    rcu_read_unlock()
                                                  ...
                                                  /* frees skb_data */
                                                  ieee80211_tx_status_ni()

/* returns (exit status doesn't matter) */
wait_for_completion_timeout()
...
/* accesses the already freed skb_data */
rcu_assign_pointer(skb_data->wait, NULL)

The completing side might proceed and free the underlying skb even before the waiting side is fully awoken and run to execution. Actually the race happens regardless of wait_for_completion_timeout() exit status, e.g. the waiting side may hit a timeout and the concurrent completing side is still able to free the skb.

Skbs which are sent by rtw89_core_tx_kick_off_and_wait() are owned by the driver. They don't come from core ieee80211 stack so no need to pass them to ieee80211_tx_status_ni() on completing side.

Introduce a work function which will act as a garbage collector for rtw89_tx_wait_info objects and the associated skbs. Thus no potentially heavy locks are required on the completing side.

Found by Linux Verification Center (linuxtesting.org).

Fixes 1ae5ca615285 ("wifi: rtw89: add function to wait for completion of TX skbs")
Cc [email protected]
Suggested-by Zong-Zhe Yang <[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] open here
drivers/net/wireless/realtek/rtw89/core.c +24 -6
index fe059c4a6b55..ec467ae0e9e6 100644
@@ -1135,6 +1135,14 @@ rtw89_core_tx_update_desc_info(struct rtw89_dev *rtwdev,
 	}
 }
 
+static void rtw89_tx_wait_work(struct wiphy *wiphy, struct wiphy_work *work)
+{
+	struct rtw89_dev *rtwdev = container_of(work, struct rtw89_dev,
+						tx_wait_work.work);
+
+	rtw89_tx_wait_list_clear(rtwdev);
+}
+
 void rtw89_core_tx_kick_off(struct rtw89_dev *rtwdev, u8 qsel)
 {
 	u8 ch_dma;

@@ -1152,6 +1160,8 @@ int rtw89_core_tx_kick_off_and_wait(struct rtw89_dev *rtwdev, struct sk_buff *sk
 	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);

@@ -1159,18 +1169,23 @@ int rtw89_core_tx_kick_off_and_wait(struct rtw89_dev *rtwdev, struct sk_buff *sk
 	}
 
 	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));
-	if (time_left == 0)
-		ret = -ETIMEDOUT;
-	else if (!wait->tx_done)
-		ret = -EAGAIN;
 
-	rcu_assign_pointer(skb_data->wait, NULL);
-	kfree_rcu(wait, rcu_head);
+	if (time_left == 0) {
+		ret = -ETIMEDOUT;
+		list_add_tail(&wait->list, &rtwdev->tx_waits);
+		wiphy_delayed_work_queue(rtwdev->hw->wiphy, &rtwdev->tx_wait_work,
+					 RTW89_TX_WAIT_WORK_TIMEOUT);
+	} else {
+		if (!wait->tx_done)
+			ret = -EAGAIN;
+		rtw89_tx_wait_release(wait);
+	}
 
 	return ret;
 }

@@ -5548,6 +5563,7 @@ void rtw89_core_stop(struct rtw89_dev *rtwdev)
 	wiphy_work_cancel(wiphy, &btc->dhcp_notify_work);
 	wiphy_work_cancel(wiphy, &btc->icmp_notify_work);
 	cancel_delayed_work_sync(&rtwdev->txq_reinvoke_work);
+	wiphy_delayed_work_cancel(wiphy, &rtwdev->tx_wait_work);
 	wiphy_delayed_work_cancel(wiphy, &rtwdev->track_work);
 	wiphy_delayed_work_cancel(wiphy, &rtwdev->track_ps_work);
 	wiphy_delayed_work_cancel(wiphy, &rtwdev->chanctx_work);

@@ -5773,6 +5789,7 @@ int rtw89_core_init(struct rtw89_dev *rtwdev)
 		INIT_LIST_HEAD(&rtwdev->scan_info.pkt_list[band]);
 	}
 	INIT_LIST_HEAD(&rtwdev->scan_info.chan_list);
+	INIT_LIST_HEAD(&rtwdev->tx_waits);
 	INIT_WORK(&rtwdev->ba_work, rtw89_core_ba_work);
 	INIT_WORK(&rtwdev->txq_work, rtw89_core_txq_work);
 	INIT_DELAYED_WORK(&rtwdev->txq_reinvoke_work, rtw89_core_txq_reinvoke_work);

@@ -5784,6 +5801,7 @@ int rtw89_core_init(struct rtw89_dev *rtwdev)
 	wiphy_delayed_work_init(&rtwdev->coex_rfk_chk_work, rtw89_coex_rfk_chk_work);
 	wiphy_delayed_work_init(&rtwdev->cfo_track_work, rtw89_phy_cfo_track_work);
 	wiphy_delayed_work_init(&rtwdev->mcc_prepare_done_work, rtw89_mcc_prepare_done_work);
+	wiphy_delayed_work_init(&rtwdev->tx_wait_work, rtw89_tx_wait_work);
 	INIT_DELAYED_WORK(&rtwdev->forbid_ba_work, rtw89_forbid_ba_work);
 	wiphy_delayed_work_init(&rtwdev->antdiv_work, rtw89_phy_antdiv_work);
 	rtwdev->txq_wq = alloc_workqueue("rtw89_tx_wq", WQ_UNBOUND | WQ_HIGHPRI, 0);
drivers/net/wireless/realtek/rtw89/core.h +33 -2
index 3d4ad2ffb75c..d15fa70eb4dc 100644
@@ -3507,9 +3507,12 @@ struct rtw89_phy_rate_pattern {
 	bool enable;
 };
 
+#define RTW89_TX_WAIT_WORK_TIMEOUT msecs_to_jiffies(500)
 struct rtw89_tx_wait_info {
 	struct rcu_head rcu_head;
+	struct list_head list;
 	struct completion completion;
+	struct sk_buff *skb;
 	bool tx_done;
 };
 

@@ -6000,6 +6003,9 @@ struct rtw89_dev {
 	/* used to protect rpwm */
 	spinlock_t rpwm_lock;
 
+	struct list_head tx_waits;
+	struct wiphy_delayed_work tx_wait_work;
+
 	struct rtw89_cam_info cam_info;
 
 	struct sk_buff_head c2h_queue;

@@ -6256,6 +6262,26 @@ rtw89_assoc_link_rcu_dereference(struct rtw89_dev *rtwdev, u8 macid)
 	list_first_entry_or_null(&p->dlink_pool, typeof(*p->links_inst), dlink_schd); \
 })
 
+static inline void rtw89_tx_wait_release(struct rtw89_tx_wait_info *wait)
+{
+	dev_kfree_skb_any(wait->skb);
+	kfree_rcu(wait, rcu_head);
+}
+
+static inline void rtw89_tx_wait_list_clear(struct rtw89_dev *rtwdev)
+{
+	struct rtw89_tx_wait_info *wait, *tmp;
+
+	lockdep_assert_wiphy(rtwdev->hw->wiphy);
+
+	list_for_each_entry_safe(wait, tmp, &rtwdev->tx_waits, list) {
+		if (!completion_done(&wait->completion))
+			continue;
+		list_del(&wait->list);
+		rtw89_tx_wait_release(wait);
+	}
+}
+
 static inline int rtw89_hci_tx_write(struct rtw89_dev *rtwdev,
 				     struct rtw89_core_tx_request *tx_req)
 {

@@ -6265,6 +6291,7 @@ static inline int rtw89_hci_tx_write(struct rtw89_dev *rtwdev,
 static inline void rtw89_hci_reset(struct rtw89_dev *rtwdev)
 {
 	rtwdev->hci.ops->reset(rtwdev);
+	rtw89_tx_wait_list_clear(rtwdev);
 }
 
 static inline int rtw89_hci_start(struct rtw89_dev *rtwdev)

@@ -7345,11 +7372,12 @@ static inline struct sk_buff *rtw89_alloc_skb_for_rx(struct rtw89_dev *rtwdev,
 	return dev_alloc_skb(length);
 }
 
-static inline void rtw89_core_tx_wait_complete(struct rtw89_dev *rtwdev,
+static inline bool rtw89_core_tx_wait_complete(struct rtw89_dev *rtwdev,
 					       struct rtw89_tx_skb_data *skb_data,
 					       bool tx_done)
 {
 	struct rtw89_tx_wait_info *wait;
+	bool ret = false;
 
 	rcu_read_lock();
 

@@ -7357,11 +7385,14 @@ static inline void rtw89_core_tx_wait_complete(struct rtw89_dev *rtwdev,
 	if (!wait)
 		goto out;
 
+	ret = true;
 	wait->tx_done = tx_done;
-	complete(&wait->completion);
+	/* Don't access skb anymore after completion */
+	complete_all(&wait->completion);
 
 out:
 	rcu_read_unlock();
+	return ret;
 }
 
 static inline bool rtw89_is_mlo_1_1(struct rtw89_dev *rtwdev)
drivers/net/wireless/realtek/rtw89/pci.c +2 -1
index c8286eb84276..8dd91d867ea6 100644
@@ -464,7 +464,8 @@ static void rtw89_pci_tx_status(struct rtw89_dev *rtwdev,
 	struct rtw89_tx_skb_data *skb_data = RTW89_TX_SKB_CB(skb);
 	struct ieee80211_tx_info *info;
 
-	rtw89_core_tx_wait_complete(rtwdev, skb_data, tx_status == RTW89_TX_DONE);
+	if (rtw89_core_tx_wait_complete(rtwdev, skb_data, tx_status == RTW89_TX_DONE))
+		return;
 
 	info = IEEE80211_SKB_CB(skb);
 	ieee80211_tx_info_clear_status(info);
drivers/net/wireless/realtek/rtw89/ser.c +2 -0
index bb39fdbcba0d..fe7beff8c424 100644
@@ -502,7 +502,9 @@ static void ser_reset_trx_st_hdl(struct rtw89_ser *ser, u8 evt)
 		}
 
 		drv_stop_rx(ser);
+		wiphy_lock(wiphy);
 		drv_trx_reset(ser);
+		wiphy_unlock(wiphy);
 
 		/* wait m3 */
 		hal_send_m2_event(ser);
maintainer
#1 lore raw

PATCH 1/2 wifi: rtw89: mcc: stop TX during MCC prepare

From: Chih-Kang Chang <[email protected]>

[ Upstream commit 182c7ff8b87e4edbb2227ede39ae0952da7a0f4a ]

Stop TX during the MCC configuration period to prevent packet leakage. The stop time is defined as 'start_tsf - tsf', which means the duration from when MCC configuration begins until MCC starts.

Signed-off-by Chih-Kang Chang <[email protected]>
Signed-off-by Ping-Ke Shih <[email protected]>
Link https://patch.msgid.link/[email protected] open here

Stable-dep-of: 3e31a6bc0731 ("wifi: rtw89: fix use-after-free in rtw89_core_tx_kick_off_and_wait()")

Signed-off-by Sasha Levin <[email protected]>
---
 drivers/net/wireless/realtek/rtw89/chan.c | 35 +++++++++++++++++++++++
 drivers/net/wireless/realtek/rtw89/chan.h |  2 ++
 drivers/net/wireless/realtek/rtw89/core.c |  2 ++
 drivers/net/wireless/realtek/rtw89/core.h |  2 ++
 4 files changed, 41 insertions(+)
drivers/net/wireless/realtek/rtw89/chan.c +35 -0
index b18019b53181c..17daf93fec0a4 100644
@@ -1595,6 +1595,35 @@ static bool rtw89_mcc_duration_decision_on_bt(struct rtw89_dev *rtwdev)
 	return false;
 }
 
+void rtw89_mcc_prepare_done_work(struct wiphy *wiphy, struct wiphy_work *work)
+{
+	struct rtw89_dev *rtwdev = container_of(work, struct rtw89_dev,
+						mcc_prepare_done_work.work);
+
+	lockdep_assert_wiphy(wiphy);
+
+	ieee80211_wake_queues(rtwdev->hw);
+}
+
+static void rtw89_mcc_prepare(struct rtw89_dev *rtwdev, bool start)
+{
+	struct rtw89_mcc_info *mcc = &rtwdev->mcc;
+	struct rtw89_mcc_config *config = &mcc->config;
+
+	if (start) {
+		ieee80211_stop_queues(rtwdev->hw);
+
+		wiphy_delayed_work_queue(rtwdev->hw->wiphy,
+					 &rtwdev->mcc_prepare_done_work,
+					 usecs_to_jiffies(config->prepare_delay));
+	} else {
+		wiphy_delayed_work_queue(rtwdev->hw->wiphy,
+					 &rtwdev->mcc_prepare_done_work, 0);
+		wiphy_delayed_work_flush(rtwdev->hw->wiphy,
+					 &rtwdev->mcc_prepare_done_work);
+	}
+}
+
 static int rtw89_mcc_fill_start_tsf(struct rtw89_dev *rtwdev)
 {
 	struct rtw89_mcc_info *mcc = &rtwdev->mcc;

@@ -1630,6 +1659,8 @@ static int rtw89_mcc_fill_start_tsf(struct rtw89_dev *rtwdev)
 
 	config->start_tsf = start_tsf;
 	config->start_tsf_in_aux_domain = tsf_aux + start_tsf - tsf;
+	config->prepare_delay = start_tsf - tsf;
+
 	return 0;
 }
 

@@ -2219,6 +2250,8 @@ static int rtw89_mcc_start(struct rtw89_dev *rtwdev)
 	rtw89_chanctx_notify(rtwdev, RTW89_CHANCTX_STATE_MCC_START);
 
 	rtw89_mcc_start_beacon_noa(rtwdev);
+
+	rtw89_mcc_prepare(rtwdev, true);
 	return 0;
 }
 

@@ -2307,6 +2340,8 @@ static void rtw89_mcc_stop(struct rtw89_dev *rtwdev,
 	rtw89_chanctx_notify(rtwdev, RTW89_CHANCTX_STATE_MCC_STOP);
 
 	rtw89_mcc_stop_beacon_noa(rtwdev);
+
+	rtw89_mcc_prepare(rtwdev, false);
 }
 
 static int rtw89_mcc_update(struct rtw89_dev *rtwdev)
drivers/net/wireless/realtek/rtw89/chan.h +2 -0
index 2a25563593af9..be998fdd8724b 100644
@@ -129,6 +129,8 @@ const struct rtw89_chan *__rtw89_mgnt_chan_get(struct rtw89_dev *rtwdev,
 #define rtw89_mgnt_chan_get(rtwdev, link_index) \
 	__rtw89_mgnt_chan_get(rtwdev, __func__, link_index)
 
+void rtw89_mcc_prepare_done_work(struct wiphy *wiphy, struct wiphy_work *work);
+
 int rtw89_chanctx_ops_add(struct rtw89_dev *rtwdev,
 			  struct ieee80211_chanctx_conf *ctx);
 void rtw89_chanctx_ops_remove(struct rtw89_dev *rtwdev,
drivers/net/wireless/realtek/rtw89/core.c +2 -0
index 894ab7ab94ccb..0e4d5679e426c 100644
@@ -4816,6 +4816,7 @@ void rtw89_core_stop(struct rtw89_dev *rtwdev)
 	wiphy_delayed_work_cancel(wiphy, &rtwdev->coex_bt_devinfo_work);
 	wiphy_delayed_work_cancel(wiphy, &rtwdev->coex_rfk_chk_work);
 	wiphy_delayed_work_cancel(wiphy, &rtwdev->cfo_track_work);
+	wiphy_delayed_work_cancel(wiphy, &rtwdev->mcc_prepare_done_work);
 	cancel_delayed_work_sync(&rtwdev->forbid_ba_work);
 	wiphy_delayed_work_cancel(wiphy, &rtwdev->antdiv_work);
 

@@ -5042,6 +5043,7 @@ int rtw89_core_init(struct rtw89_dev *rtwdev)
 	wiphy_delayed_work_init(&rtwdev->coex_bt_devinfo_work, rtw89_coex_bt_devinfo_work);
 	wiphy_delayed_work_init(&rtwdev->coex_rfk_chk_work, rtw89_coex_rfk_chk_work);
 	wiphy_delayed_work_init(&rtwdev->cfo_track_work, rtw89_phy_cfo_track_work);
+	wiphy_delayed_work_init(&rtwdev->mcc_prepare_done_work, rtw89_mcc_prepare_done_work);
 	INIT_DELAYED_WORK(&rtwdev->forbid_ba_work, rtw89_forbid_ba_work);
 	wiphy_delayed_work_init(&rtwdev->antdiv_work, rtw89_phy_antdiv_work);
 	rtwdev->txq_wq = alloc_workqueue("rtw89_tx_wq", WQ_UNBOUND | WQ_HIGHPRI, 0);
drivers/net/wireless/realtek/rtw89/core.h +2 -0
index 1c8f3b9b7c4c6..f505fe6da4a24 100644
@@ -5728,6 +5728,7 @@ struct rtw89_mcc_config {
 	struct rtw89_mcc_sync sync;
 	u64 start_tsf;
 	u64 start_tsf_in_aux_domain;
+	u64 prepare_delay;
 	u16 mcc_interval; /* TU */
 	u16 beacon_offset; /* TU */
 };

@@ -5858,6 +5859,7 @@ struct rtw89_dev {
 	struct wiphy_delayed_work coex_bt_devinfo_work;
 	struct wiphy_delayed_work coex_rfk_chk_work;
 	struct wiphy_delayed_work cfo_track_work;
+	struct wiphy_delayed_work mcc_prepare_done_work;
 	struct delayed_work forbid_ba_work;
 	struct wiphy_delayed_work antdiv_work;
 	struct rtw89_ppdu_sts_info ppdu_sts;
Signature · 1 line
2.51.0
maintainer
#2 lore raw

PATCH 2/2 wifi: rtw89: fix use-after-free in rtw89_core_tx_kick_off_and_wait()

From: Fedor Pchelkin <[email protected]>

[ Upstream commit 3e31a6bc07312b448fad3b45de578471f86f0e77 ]

There is a bug observed when rtw89_core_tx_kick_off_and_wait() tries to access already freed skb_data:

 BUG: KFENCE: use-after-free write in rtw89_core_tx_kick_off_and_wait drivers/net/wireless/realtek/rtw89/core.c:1110

 CPU: 6 UID: 0 PID: 41377 Comm: kworker/u64:24 Not tainted  6.17.0-rc1+ #1 PREEMPT(lazy)
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS edk2-20250523-14.fc42 05/23/2025
 Workqueue: events_unbound cfg80211_wiphy_work [cfg80211]

Use-after-free write at 0x0000000020309d9d (in kfence-#251):

 rtw89_core_tx_kick_off_and_wait drivers/net/wireless/realtek/rtw89/core.c:1110
 rtw89_core_scan_complete drivers/net/wireless/realtek/rtw89/core.c:5338
 rtw89_hw_scan_complete_cb drivers/net/wireless/realtek/rtw89/fw.c:7979
 rtw89_chanctx_proceed_cb drivers/net/wireless/realtek/rtw89/chan.c:3165
 rtw89_chanctx_proceed drivers/net/wireless/realtek/rtw89/chan.h:141
 rtw89_hw_scan_complete drivers/net/wireless/realtek/rtw89/fw.c:8012
 rtw89_mac_c2h_scanofld_rsp drivers/net/wireless/realtek/rtw89/mac.c:5059
 rtw89_fw_c2h_work drivers/net/wireless/realtek/rtw89/fw.c:6758
 process_one_work kernel/workqueue.c:3241
 worker_thread kernel/workqueue.c:3400
 kthread kernel/kthread.c:463
 ret_from_fork arch/x86/kernel/process.c:154
 ret_from_fork_asm arch/x86/entry/entry_64.S:258

kfence-#251: 0x0000000056e2393d-0x000000009943cb62, size=232, cache=skbuff_head_cache

allocated by task 41377 on cpu 6 at 77869.159548s (0.009551s ago):

 __alloc_skb net/core/skbuff.c:659
 __netdev_alloc_skb net/core/skbuff.c:734
 ieee80211_nullfunc_get net/mac80211/tx.c:5844
 rtw89_core_send_nullfunc drivers/net/wireless/realtek/rtw89/core.c:3431
 rtw89_core_scan_complete drivers/net/wireless/realtek/rtw89/core.c:5338
 rtw89_hw_scan_complete_cb drivers/net/wireless/realtek/rtw89/fw.c:7979
 rtw89_chanctx_proceed_cb drivers/net/wireless/realtek/rtw89/chan.c:3165
 rtw89_chanctx_proceed drivers/net/wireless/realtek/rtw89/chan.c:3194
 rtw89_hw_scan_complete drivers/net/wireless/realtek/rtw89/fw.c:8012
 rtw89_mac_c2h_scanofld_rsp drivers/net/wireless/realtek/rtw89/mac.c:5059
 rtw89_fw_c2h_work drivers/net/wireless/realtek/rtw89/fw.c:6758
 process_one_work kernel/workqueue.c:3241
 worker_thread kernel/workqueue.c:3400
 kthread kernel/kthread.c:463
 ret_from_fork arch/x86/kernel/process.c:154
 ret_from_fork_asm arch/x86/entry/entry_64.S:258

freed by task 1045 on cpu 9 at 77869.168393s (0.001557s ago):

 ieee80211_tx_status_skb net/mac80211/status.c:1117
 rtw89_pci_release_txwd_skb drivers/net/wireless/realtek/rtw89/pci.c:564
 rtw89_pci_release_tx_skbs.isra.0 drivers/net/wireless/realtek/rtw89/pci.c:651
 rtw89_pci_release_tx drivers/net/wireless/realtek/rtw89/pci.c:676
 rtw89_pci_napi_poll drivers/net/wireless/realtek/rtw89/pci.c:4238
 __napi_poll net/core/dev.c:7495
 net_rx_action net/core/dev.c:7557 net/core/dev.c:7684
 handle_softirqs kernel/softirq.c:580
 do_softirq.part.0 kernel/softirq.c:480
 __local_bh_enable_ip kernel/softirq.c:407
 rtw89_pci_interrupt_threadfn drivers/net/wireless/realtek/rtw89/pci.c:927
 irq_thread_fn kernel/irq/manage.c:1133
 irq_thread kernel/irq/manage.c:1257
 kthread kernel/kthread.c:463
 ret_from_fork arch/x86/kernel/process.c:154
 ret_from_fork_asm arch/x86/entry/entry_64.S:258

It is a consequence of a race between the waiting and the signaling side of the completion:

Waiting thread Completing thread

rtw89_core_tx_kick_off_and_wait()
rcu_assign_pointer(skb_data->wait, wait)
/* start waiting */
wait_for_completion_timeout()

                                                rtw89_pci_tx_status()
                                                  rtw89_core_tx_wait_complete()
                                                    rcu_read_lock()
                                                    /* signals completion and
                                                     * proceeds further
                                                     */
                                                    complete(&wait->completion)
                                                    rcu_read_unlock()
                                                  ...
                                                  /* frees skb_data */
                                                  ieee80211_tx_status_ni()

/* returns (exit status doesn't matter) */
wait_for_completion_timeout()
...
/* accesses the already freed skb_data */
rcu_assign_pointer(skb_data->wait, NULL)

The completing side might proceed and free the underlying skb even before the waiting side is fully awoken and run to execution. Actually the race happens regardless of wait_for_completion_timeout() exit status, e.g. the waiting side may hit a timeout and the concurrent completing side is still able to free the skb.

Skbs which are sent by rtw89_core_tx_kick_off_and_wait() are owned by the driver. They don't come from core ieee80211 stack so no need to pass them to ieee80211_tx_status_ni() on completing side.

Introduce a work function which will act as a garbage collector for rtw89_tx_wait_info objects and the associated skbs. Thus no potentially heavy locks are required on the completing side.

Found by Linux Verification Center (linuxtesting.org).

Fixes 1ae5ca615285 ("wifi: rtw89: add function to wait for completion of TX skbs")
Cc [email protected]
Suggested-by Zong-Zhe Yang <[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] open here
Signed-off-by Sasha Levin <[email protected]>
---
 drivers/net/wireless/realtek/rtw89/core.c | 30 +++++++++++++++----
 drivers/net/wireless/realtek/rtw89/core.h | 35 +++++++++++++++++++++--
 drivers/net/wireless/realtek/rtw89/pci.c  |  3 +-
 drivers/net/wireless/realtek/rtw89/ser.c  |  2 ++
 4 files changed, 61 insertions(+), 9 deletions(-)
drivers/net/wireless/realtek/rtw89/core.c +24 -6
index 0e4d5679e426c..b506afaaa3ec9 100644
@@ -1050,6 +1050,14 @@ rtw89_core_tx_update_desc_info(struct rtw89_dev *rtwdev,
 	}
 }
 
+static void rtw89_tx_wait_work(struct wiphy *wiphy, struct wiphy_work *work)
+{
+	struct rtw89_dev *rtwdev = container_of(work, struct rtw89_dev,
+						tx_wait_work.work);
+
+	rtw89_tx_wait_list_clear(rtwdev);
+}
+
 void rtw89_core_tx_kick_off(struct rtw89_dev *rtwdev, u8 qsel)
 {
 	u8 ch_dma;

@@ -1067,6 +1075,8 @@ int rtw89_core_tx_kick_off_and_wait(struct rtw89_dev *rtwdev, struct sk_buff *sk
 	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);

@@ -1074,18 +1084,23 @@ int rtw89_core_tx_kick_off_and_wait(struct rtw89_dev *rtwdev, struct sk_buff *sk
 	}
 
 	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));
-	if (time_left == 0)
-		ret = -ETIMEDOUT;
-	else if (!wait->tx_done)
-		ret = -EAGAIN;
 
-	rcu_assign_pointer(skb_data->wait, NULL);
-	kfree_rcu(wait, rcu_head);
+	if (time_left == 0) {
+		ret = -ETIMEDOUT;
+		list_add_tail(&wait->list, &rtwdev->tx_waits);
+		wiphy_delayed_work_queue(rtwdev->hw->wiphy, &rtwdev->tx_wait_work,
+					 RTW89_TX_WAIT_WORK_TIMEOUT);
+	} else {
+		if (!wait->tx_done)
+			ret = -EAGAIN;
+		rtw89_tx_wait_release(wait);
+	}
 
 	return ret;
 }

@@ -4810,6 +4825,7 @@ void rtw89_core_stop(struct rtw89_dev *rtwdev)
 	wiphy_work_cancel(wiphy, &btc->dhcp_notify_work);
 	wiphy_work_cancel(wiphy, &btc->icmp_notify_work);
 	cancel_delayed_work_sync(&rtwdev->txq_reinvoke_work);
+	wiphy_delayed_work_cancel(wiphy, &rtwdev->tx_wait_work);
 	wiphy_delayed_work_cancel(wiphy, &rtwdev->track_work);
 	wiphy_delayed_work_cancel(wiphy, &rtwdev->chanctx_work);
 	wiphy_delayed_work_cancel(wiphy, &rtwdev->coex_act1_work);

@@ -5034,6 +5050,7 @@ int rtw89_core_init(struct rtw89_dev *rtwdev)
 		INIT_LIST_HEAD(&rtwdev->scan_info.pkt_list[band]);
 	}
 	INIT_LIST_HEAD(&rtwdev->scan_info.chan_list);
+	INIT_LIST_HEAD(&rtwdev->tx_waits);
 	INIT_WORK(&rtwdev->ba_work, rtw89_core_ba_work);
 	INIT_WORK(&rtwdev->txq_work, rtw89_core_txq_work);
 	INIT_DELAYED_WORK(&rtwdev->txq_reinvoke_work, rtw89_core_txq_reinvoke_work);

@@ -5044,6 +5061,7 @@ int rtw89_core_init(struct rtw89_dev *rtwdev)
 	wiphy_delayed_work_init(&rtwdev->coex_rfk_chk_work, rtw89_coex_rfk_chk_work);
 	wiphy_delayed_work_init(&rtwdev->cfo_track_work, rtw89_phy_cfo_track_work);
 	wiphy_delayed_work_init(&rtwdev->mcc_prepare_done_work, rtw89_mcc_prepare_done_work);
+	wiphy_delayed_work_init(&rtwdev->tx_wait_work, rtw89_tx_wait_work);
 	INIT_DELAYED_WORK(&rtwdev->forbid_ba_work, rtw89_forbid_ba_work);
 	wiphy_delayed_work_init(&rtwdev->antdiv_work, rtw89_phy_antdiv_work);
 	rtwdev->txq_wq = alloc_workqueue("rtw89_tx_wq", WQ_UNBOUND | WQ_HIGHPRI, 0);
drivers/net/wireless/realtek/rtw89/core.h +33 -2
index f505fe6da4a24..e2e90eab15ce0 100644
@@ -3429,9 +3429,12 @@ struct rtw89_phy_rate_pattern {
 	bool enable;
 };
 
+#define RTW89_TX_WAIT_WORK_TIMEOUT msecs_to_jiffies(500)
 struct rtw89_tx_wait_info {
 	struct rcu_head rcu_head;
+	struct list_head list;
 	struct completion completion;
+	struct sk_buff *skb;
 	bool tx_done;
 };
 

@@ -5802,6 +5805,9 @@ struct rtw89_dev {
 	/* used to protect rpwm */
 	spinlock_t rpwm_lock;
 
+	struct list_head tx_waits;
+	struct wiphy_delayed_work tx_wait_work;
+
 	struct rtw89_cam_info cam_info;
 
 	struct sk_buff_head c2h_queue;

@@ -6056,6 +6062,26 @@ rtw89_assoc_link_rcu_dereference(struct rtw89_dev *rtwdev, u8 macid)
 	list_first_entry_or_null(&p->dlink_pool, typeof(*p->links_inst), dlink_schd); \
 })
 
+static inline void rtw89_tx_wait_release(struct rtw89_tx_wait_info *wait)
+{
+	dev_kfree_skb_any(wait->skb);
+	kfree_rcu(wait, rcu_head);
+}
+
+static inline void rtw89_tx_wait_list_clear(struct rtw89_dev *rtwdev)
+{
+	struct rtw89_tx_wait_info *wait, *tmp;
+
+	lockdep_assert_wiphy(rtwdev->hw->wiphy);
+
+	list_for_each_entry_safe(wait, tmp, &rtwdev->tx_waits, list) {
+		if (!completion_done(&wait->completion))
+			continue;
+		list_del(&wait->list);
+		rtw89_tx_wait_release(wait);
+	}
+}
+
 static inline int rtw89_hci_tx_write(struct rtw89_dev *rtwdev,
 				     struct rtw89_core_tx_request *tx_req)
 {

@@ -6065,6 +6091,7 @@ static inline int rtw89_hci_tx_write(struct rtw89_dev *rtwdev,
 static inline void rtw89_hci_reset(struct rtw89_dev *rtwdev)
 {
 	rtwdev->hci.ops->reset(rtwdev);
+	rtw89_tx_wait_list_clear(rtwdev);
 }
 
 static inline int rtw89_hci_start(struct rtw89_dev *rtwdev)

@@ -7122,11 +7149,12 @@ static inline struct sk_buff *rtw89_alloc_skb_for_rx(struct rtw89_dev *rtwdev,
 	return dev_alloc_skb(length);
 }
 
-static inline void rtw89_core_tx_wait_complete(struct rtw89_dev *rtwdev,
+static inline bool rtw89_core_tx_wait_complete(struct rtw89_dev *rtwdev,
 					       struct rtw89_tx_skb_data *skb_data,
 					       bool tx_done)
 {
 	struct rtw89_tx_wait_info *wait;
+	bool ret = false;
 
 	rcu_read_lock();
 

@@ -7134,11 +7162,14 @@ static inline void rtw89_core_tx_wait_complete(struct rtw89_dev *rtwdev,
 	if (!wait)
 		goto out;
 
+	ret = true;
 	wait->tx_done = tx_done;
-	complete(&wait->completion);
+	/* Don't access skb anymore after completion */
+	complete_all(&wait->completion);
 
 out:
 	rcu_read_unlock();
+	return ret;
 }
 
 static inline bool rtw89_is_mlo_1_1(struct rtw89_dev *rtwdev)
drivers/net/wireless/realtek/rtw89/pci.c +2 -1
index 064f6a9401073..8eeb1a4498cd8 100644
@@ -464,7 +464,8 @@ static void rtw89_pci_tx_status(struct rtw89_dev *rtwdev,
 	struct rtw89_tx_skb_data *skb_data = RTW89_TX_SKB_CB(skb);
 	struct ieee80211_tx_info *info;
 
-	rtw89_core_tx_wait_complete(rtwdev, skb_data, tx_status == RTW89_TX_DONE);
+	if (rtw89_core_tx_wait_complete(rtwdev, skb_data, tx_status == RTW89_TX_DONE))
+		return;
 
 	info = IEEE80211_SKB_CB(skb);
 	ieee80211_tx_info_clear_status(info);
drivers/net/wireless/realtek/rtw89/ser.c +2 -0
index 811c914814411..869ab22a79681 100644
@@ -501,7 +501,9 @@ static void ser_reset_trx_st_hdl(struct rtw89_ser *ser, u8 evt)
 		}
 
 		drv_stop_rx(ser);
+		wiphy_lock(wiphy);
 		drv_trx_reset(ser);
+		wiphy_unlock(wiphy);
 
 		/* wait m3 */
 		hal_send_m2_event(ser);
Signature · 1 line
2.51.0