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Message-ID: <20250828211245.178843-2-pchelkin@ispras.ru>
Date: Fri, 29 Aug 2025 00:11:57 +0300
From: Fedor Pchelkin <pchelkin@...ras.ru>
To: Ping-Ke Shih <pkshih@...ltek.com>,
Zong-Zhe Yang <kevin_yang@...ltek.com>,
Bitterblue Smith <rtl8821cerfe2@...il.com>
Cc: Fedor Pchelkin <pchelkin@...ras.ru>,
Po-Hao Huang <phhuang@...ltek.com>,
linux-wireless@...r.kernel.org,
linux-kernel@...r.kernel.org,
lvc-project@...uxtesting.org,
stable@...r.kernel.org
Subject: [PATCH rtw v3 1/5] 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: stable@...r.kernel.org
Suggested-by: Zong-Zhe Yang <kevin_yang@...ltek.com>
Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>
---
v3: - decrease waiting timeout in rtw89_tx_wait_work() (Zong-Zhe)
- clear tx_waits list from rtw89_hci_reset(), too (Zong-Zhe)
- keep RCU updating for skb_data->wait (Zong-Zhe)
- keep the old order of calls in rtw89_pci_tx_status() (Zong-Zhe)
- drop wait->finished as complete_all() would make the completion be
done permanently (me)
v2: - use a work function to manage release of tx_waits and associated skbs (Zong-Zhe)
FWIW, I think RCU locking becomes unnecessary after the next patch
[PATCH rtw v3 2/5] wifi: rtw89: fix tx_wait initialization race
but let's keep it if you feel that's more safe.
drivers/net/wireless/realtek/rtw89/core.c | 28 ++++++++++++++---
drivers/net/wireless/realtek/rtw89/core.h | 38 +++++++++++++++++++++--
drivers/net/wireless/realtek/rtw89/pci.c | 3 +-
drivers/net/wireless/realtek/rtw89/ser.c | 2 ++
4 files changed, 63 insertions(+), 8 deletions(-)
diff --git a/drivers/net/wireless/realtek/rtw89/core.c b/drivers/net/wireless/realtek/rtw89/core.c
index 57590f5577a3..5c964283cd67 100644
--- a/drivers/net/wireless/realtek/rtw89/core.c
+++ b/drivers/net/wireless/realtek/rtw89/core.c
@@ -1073,6 +1073,14 @@ 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);
+
+ rtw89_tx_wait_list_clear(rtwdev);
+}
+
void rtw89_core_tx_kick_off(struct rtw89_dev *rtwdev, u8 qsel)
{
u8 ch_dma;
@@ -1090,6 +1098,8 @@ 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);
@@ -1098,17 +1108,22 @@ int rtw89_core_tx_kick_off_and_wait(struct rtw89_dev *rtwdev, struct sk_buff *sk
init_completion(&wait->completion);
rcu_assign_pointer(skb_data->wait, wait);
+ wait->skb = skb;
rtw89_core_tx_kick_off(rtwdev, qsel);
time_left = wait_for_completion_timeout(&wait->completion,
msecs_to_jiffies(timeout));
- if (time_left == 0)
+
+ if (time_left == 0) {
ret = -ETIMEDOUT;
- else if (!wait->tx_done)
- ret = -EAGAIN;
+ list_add_tail(&wait->list, &rtwdev->tx_waits);
+ wiphy_work_queue(rtwdev->hw->wiphy, &rtwdev->tx_wait_work);
- rcu_assign_pointer(skb_data->wait, NULL);
- kfree_rcu(wait, rcu_head);
+ } else {
+ if (!wait->tx_done)
+ ret = -EAGAIN;
+ rtw89_tx_wait_release(&wait->rcu_head);
+ }
return ret;
}
@@ -4972,6 +4987,7 @@ void rtw89_core_stop(struct rtw89_dev *rtwdev)
clear_bit(RTW89_FLAG_RUNNING, rtwdev->flags);
wiphy_work_cancel(wiphy, &rtwdev->c2h_work);
+ wiphy_work_cancel(wiphy, &rtwdev->tx_wait_work);
wiphy_work_cancel(wiphy, &rtwdev->cancel_6ghz_probe_work);
wiphy_work_cancel(wiphy, &btc->eapol_notify_work);
wiphy_work_cancel(wiphy, &btc->arp_notify_work);
@@ -5203,6 +5219,7 @@ 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);
@@ -5233,6 +5250,7 @@ int rtw89_core_init(struct rtw89_dev *rtwdev)
wiphy_work_init(&rtwdev->c2h_work, rtw89_fw_c2h_work);
wiphy_work_init(&rtwdev->ips_work, rtw89_ips_work);
wiphy_work_init(&rtwdev->cancel_6ghz_probe_work, rtw89_cancel_6ghz_probe_work);
+ wiphy_work_init(&rtwdev->tx_wait_work, rtw89_tx_wait_work);
INIT_WORK(&rtwdev->load_firmware_work, rtw89_load_firmware_work);
skb_queue_head_init(&rtwdev->c2h_queue);
diff --git a/drivers/net/wireless/realtek/rtw89/core.h b/drivers/net/wireless/realtek/rtw89/core.h
index 43e10278e14d..9b22bb116af9 100644
--- a/drivers/net/wireless/realtek/rtw89/core.h
+++ b/drivers/net/wireless/realtek/rtw89/core.h
@@ -3506,9 +3506,12 @@ struct rtw89_phy_rate_pattern {
bool enable;
};
+#define RTW89_TX_WAIT_DEFAULT_TIMEOUT 10
struct rtw89_tx_wait_info {
struct rcu_head rcu_head;
+ struct list_head list;
struct completion completion;
+ struct sk_buff *skb;
bool tx_done;
};
@@ -5925,6 +5928,9 @@ struct rtw89_dev {
/* used to protect rpwm */
spinlock_t rpwm_lock;
+ struct list_head tx_waits;
+ struct wiphy_work tx_wait_work;
+
struct rtw89_cam_info cam_info;
struct sk_buff_head c2h_queue;
@@ -6181,6 +6187,30 @@ 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 rcu_head *rcu_head)
+{
+ struct rtw89_tx_wait_info *wait =
+ container_of(rcu_head, struct rtw89_tx_wait_info, rcu_head);
+
+ dev_kfree_skb_any(wait->skb);
+ kfree(wait);
+}
+
+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 (!wait_for_completion_timeout(&wait->completion,
+ RTW89_TX_WAIT_DEFAULT_TIMEOUT))
+ continue;
+ list_del(&wait->list);
+ call_rcu(&wait->rcu_head, rtw89_tx_wait_release);
+ }
+}
+
static inline int rtw89_hci_tx_write(struct rtw89_dev *rtwdev,
struct rtw89_core_tx_request *tx_req)
{
@@ -6190,6 +6220,7 @@ 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)
@@ -7258,11 +7289,12 @@ 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();
@@ -7270,11 +7302,13 @@ 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);
+ complete_all(&wait->completion);
out:
rcu_read_unlock();
+ return ret;
}
static inline bool rtw89_is_mlo_1_1(struct rtw89_dev *rtwdev)
diff --git a/drivers/net/wireless/realtek/rtw89/pci.c b/drivers/net/wireless/realtek/rtw89/pci.c
index a669f2f843aa..4e3034b44f56 100644
--- a/drivers/net/wireless/realtek/rtw89/pci.c
+++ b/drivers/net/wireless/realtek/rtw89/pci.c
@@ -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);
diff --git a/drivers/net/wireless/realtek/rtw89/ser.c b/drivers/net/wireless/realtek/rtw89/ser.c
index bb39fdbcba0d..fe7beff8c424 100644
--- a/drivers/net/wireless/realtek/rtw89/ser.c
+++ b/drivers/net/wireless/realtek/rtw89/ser.c
@@ -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);
--
2.51.0
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