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Message-ID: <20250827120603.723548-2-pchelkin@ispras.ru>
Date: Wed, 27 Aug 2025 15:05:14 +0300
From: Fedor Pchelkin <pchelkin@...ras.ru>
To: Ping-Ke Shih <pkshih@...ltek.com>,
Zong-Zhe Yang <kevin_yang@...ltek.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 v2 1/4] 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>
---
v2: use a work function to manage release of tx_waits and associated skbs (Zong-Zhe)
The interesting part is how rtw89_tx_wait_work() should wait for
completion - based on timeout or without it, or just check status with
a call to completion_done().
Simply waiting with wait_for_completion() may become a bottleneck if for
any reason the completion is delayed significantly, and we are holding a
wiphy lock here. I _suspect_ rtw89_pci_tx_status() should be called
either by napi polling handler or in other cases e.g. by rtw89_hci_reset()
but it's hard to deduce for any possible scenario that it will be called
in some time.
Anyway, the current and the next patch try to make sure that when
rtw89_core_tx_wait_complete() is called, skbdata->wait is properly
initialized so that there should be no buggy situations when tx_wait skb
is not recognized and invalidly passed to ieee80211 stack, also without
signaling a completion.
If rtw89_core_tx_wait_complete() is not called at all, this should
indicate a bug elsewhere.
drivers/net/wireless/realtek/rtw89/core.c | 42 +++++++++++++++++++----
drivers/net/wireless/realtek/rtw89/core.h | 22 +++++++-----
drivers/net/wireless/realtek/rtw89/pci.c | 9 ++---
3 files changed, 54 insertions(+), 19 deletions(-)
diff --git a/drivers/net/wireless/realtek/rtw89/core.c b/drivers/net/wireless/realtek/rtw89/core.c
index 57590f5577a3..48aa02d6abd4 100644
--- a/drivers/net/wireless/realtek/rtw89/core.c
+++ b/drivers/net/wireless/realtek/rtw89/core.c
@@ -1073,6 +1073,26 @@ 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);
+ struct rtw89_tx_wait_info *wait, *tmp;
+
+ lockdep_assert_wiphy(wiphy);
+
+ list_for_each_entry_safe(wait, tmp, &rtwdev->tx_waits, list) {
+ if (!wait->finished) {
+ unsigned long tmo = msecs_to_jiffies(wait->timeout);
+ if (!wait_for_completion_timeout(&wait->completion, tmo))
+ continue;
+ }
+ list_del(&wait->list);
+ dev_kfree_skb_any(wait->skb);
+ kfree(wait);
+ }
+}
+
void rtw89_core_tx_kick_off(struct rtw89_dev *rtwdev, u8 qsel)
{
u8 ch_dma;
@@ -1090,6 +1110,8 @@ 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);
@@ -1097,18 +1119,23 @@ 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);
+ 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)
+ if (time_left == 0) {
ret = -ETIMEDOUT;
- else if (!wait->tx_done)
- ret = -EAGAIN;
+ } else {
+ wait->finished = true;
+ if (!wait->tx_done)
+ ret = -EAGAIN;
+ }
- rcu_assign_pointer(skb_data->wait, NULL);
- kfree_rcu(wait, rcu_head);
+ wait->skb = skb;
+ wait->timeout = timeout;
+ list_add_tail(&wait->list, &rtwdev->tx_waits);
+ wiphy_work_queue(rtwdev->hw->wiphy, &rtwdev->tx_wait_work);
return ret;
}
@@ -4972,6 +4999,7 @@ 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 +5231,7 @@ 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 +5262,7 @@ 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..06f7d82a8d18 100644
--- a/drivers/net/wireless/realtek/rtw89/core.h
+++ b/drivers/net/wireless/realtek/rtw89/core.h
@@ -3508,12 +3508,16 @@ struct rtw89_phy_rate_pattern {
struct rtw89_tx_wait_info {
struct rcu_head rcu_head;
+ struct list_head list;
struct completion completion;
+ struct sk_buff *skb;
+ unsigned int timeout;
bool tx_done;
+ bool finished;
};
struct rtw89_tx_skb_data {
- struct rtw89_tx_wait_info __rcu *wait;
+ struct rtw89_tx_wait_info *wait;
u8 hci_priv[];
};
@@ -5925,6 +5929,9 @@ 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;
@@ -7258,23 +7265,20 @@ 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;
- rcu_read_lock();
-
- wait = rcu_dereference(skb_data->wait);
+ wait = skb_data->wait;
if (!wait)
- goto out;
+ return false;
wait->tx_done = tx_done;
- complete(&wait->completion);
+ complete_all(&wait->completion);
-out:
- rcu_read_unlock();
+ return true;
}
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..6356c2c224c5 100644
--- a/drivers/net/wireless/realtek/rtw89/pci.c
+++ b/drivers/net/wireless/realtek/rtw89/pci.c
@@ -464,10 +464,7 @@ 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);
-
info = IEEE80211_SKB_CB(skb);
- ieee80211_tx_info_clear_status(info);
if (info->flags & IEEE80211_TX_CTL_NO_ACK)
info->flags |= IEEE80211_TX_STAT_NOACK_TRANSMITTED;
@@ -494,6 +491,10 @@ static void rtw89_pci_tx_status(struct rtw89_dev *rtwdev,
}
}
+ if (rtw89_core_tx_wait_complete(rtwdev, skb_data, tx_status == RTW89_TX_DONE))
+ return;
+
+ ieee80211_tx_info_clear_status(info);
ieee80211_tx_status_ni(rtwdev->hw, skb);
}
@@ -1387,7 +1388,7 @@ static int rtw89_pci_txwd_submit(struct rtw89_dev *rtwdev,
}
tx_data->dma = dma;
- rcu_assign_pointer(skb_data->wait, NULL);
+ skb_data->wait = NULL;
txwp_len = sizeof(*txwp_info);
txwd_len = chip->txwd_body_size;
--
2.50.1
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