[PATCH] wifi: wcn36xx: Fix potential use-after-free in TX ack timer teardown

[PATCH] wifi: wcn36xx: Fix potential use-after-free in TX ack timer teardown

[Fan Wu]

wcn36xx_dxe_deinit() tears down the TX ack timer with timer_delete(),
which only dequeues the timer and does not wait for a callback that is
already executing; the preceding free_irq() calls synchronize the
interrupt handlers only. The callback, wcn36xx_dxe_tx_timer(), can
therefore be running past the teardown and use the wcn freed along
with the ieee80211_hw in wcn36xx_remove(): it takes wcn->dxe_lock,
reads wcn->tx_ack_skb and passes wcn->hw to
ieee80211_tx_status_irqsafe().

Fix this by using timer_shutdown_sync(), which waits for a running
callback and also prevents the timer from being rearmed again. The
timer is set up again by wcn36xx_dxe_init() on the next start, so the
start/stop cycle is unaffected.

This issue was found by an in-house static analysis tool.

Fixes: fdf21cc37149 ("wcn36xx: Add TX ack support")
Cc: stable@vger.kernel.org
Assisted-by: Codex:gpt-5.6
Co-developed-by: Song Li <songl@zju.edu.cn>
Signed-off-by: Song Li <songl@zju.edu.cn>
Signed-off-by: Fan Wu <fanwu01@zju.edu.cn>
---
 drivers/net/wireless/ath/wcn36xx/dxe.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/wcn36xx/dxe.c b/drivers/net/wireless/ath/wcn36xx/dxe.c
index 44020ec26..801f1218e 100644
--- a/drivers/net/wireless/ath/wcn36xx/dxe.c
+++ b/drivers/net/wireless/ath/wcn36xx/dxe.c
@@ -1055,7 +1055,7 @@ void wcn36xx_dxe_deinit(struct wcn36xx *wcn)
 
 	free_irq(wcn->tx_irq, wcn);
 	free_irq(wcn->rx_irq, wcn);
-	timer_delete(&wcn->tx_ack_timer);
+	timer_shutdown_sync(&wcn->tx_ack_timer);
 
 	if (wcn->tx_ack_skb) {
 		ieee80211_tx_status_irqsafe(wcn->hw, wcn->tx_ack_skb);

Re: [PATCH] wifi: wcn36xx: Fix potential use-after-free in TX ack timer teardown

[Loic Poulain]

On Thu, Sep 10, 2026 at 4:10 AM Fan Wu <fanwu01@zju.edu.cn> wrote:
>
> wcn36xx_dxe_deinit() tears down the TX ack timer with timer_delete(),
> which only dequeues the timer and does not wait for a callback that is
> already executing; the preceding free_irq() calls synchronize the
> interrupt handlers only. The callback, wcn36xx_dxe_tx_timer(), can
> therefore be running past the teardown and use the wcn freed along
> with the ieee80211_hw in wcn36xx_remove(): it takes wcn->dxe_lock,
> reads wcn->tx_ack_skb and passes wcn->hw to
> ieee80211_tx_status_irqsafe().
>
> Fix this by using timer_shutdown_sync(), which waits for a running
> callback and also prevents the timer from being rearmed again. The
> timer is set up again by wcn36xx_dxe_init() on the next start, so the
> start/stop cycle is unaffected.
>
> This issue was found by an in-house static analysis tool.
>
> Fixes: fdf21cc37149 ("wcn36xx: Add TX ack support")
> Cc: stable@vger.kernel.org
> Assisted-by: Codex:gpt-5.6
> Co-developed-by: Song Li <songl@zju.edu.cn>
> Signed-off-by: Song Li <songl@zju.edu.cn>
> Signed-off-by: Fan Wu <fanwu01@zju.edu.cn>

Reviewed-by: Loic Poulain <loic.poulain@oss.qualcomm.com>

> ---
>  drivers/net/wireless/ath/wcn36xx/dxe.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/ath/wcn36xx/dxe.c b/drivers/net/wireless/ath/wcn36xx/dxe.c
> index 44020ec26..801f1218e 100644
> --- a/drivers/net/wireless/ath/wcn36xx/dxe.c
> +++ b/drivers/net/wireless/ath/wcn36xx/dxe.c
> @@ -1055,7 +1055,7 @@ void wcn36xx_dxe_deinit(struct wcn36xx *wcn)
>
>         free_irq(wcn->tx_irq, wcn);
>         free_irq(wcn->rx_irq, wcn);
> -       timer_delete(&wcn->tx_ack_timer);
> +       timer_shutdown_sync(&wcn->tx_ack_timer);
>
>         if (wcn->tx_ack_skb) {
>                 ieee80211_tx_status_irqsafe(wcn->hw, wcn->tx_ack_skb);
>

Re: [PATCH] wifi: wcn36xx: Fix potential use-after-free in TX ack timer teardown

[Jeff Johnson]

On 9/9/2026 7:09 PM, Fan Wu wrote:
> wcn36xx_dxe_deinit() tears down the TX ack timer with timer_delete(),
> which only dequeues the timer and does not wait for a callback that is
> already executing; the preceding free_irq() calls synchronize the
> interrupt handlers only. The callback, wcn36xx_dxe_tx_timer(), can
> therefore be running past the teardown and use the wcn freed along
> with the ieee80211_hw in wcn36xx_remove(): it takes wcn->dxe_lock,
> reads wcn->tx_ack_skb and passes wcn->hw to
> ieee80211_tx_status_irqsafe().
> 
> Fix this by using timer_shutdown_sync(), which waits for a running
> callback and also prevents the timer from being rearmed again. The
> timer is set up again by wcn36xx_dxe_init() on the next start, so the
> start/stop cycle is unaffected.
> 
> This issue was found by an in-house static analysis tool.
> 
> Fixes: fdf21cc37149 ("wcn36xx: Add TX ack support")
> Cc: stable@vger.kernel.org
> Assisted-by: Codex:gpt-5.6

Current guidance is to just have Assisted-by: LLM
https://docs.kernel.org/process/coding-assistants.html#attribution

No need to resend, I'll make that change when I process the patch.

/jeff

Re: [PATCH] wifi: wcn36xx: Fix potential use-after-free in TX ack timer teardown

[Jeff Johnson]

On Thu, 10 Sep 2026 02:09:07 +0000, Fan Wu wrote:
> wcn36xx_dxe_deinit() tears down the TX ack timer with timer_delete(),
> which only dequeues the timer and does not wait for a callback that is
> already executing; the preceding free_irq() calls synchronize the
> interrupt handlers only. The callback, wcn36xx_dxe_tx_timer(), can
> therefore be running past the teardown and use the wcn freed along
> with the ieee80211_hw in wcn36xx_remove(): it takes wcn->dxe_lock,
> reads wcn->tx_ack_skb and passes wcn->hw to
> ieee80211_tx_status_irqsafe().
> 
> [...]

Applied, thanks!

[1/1] wifi: wcn36xx: Fix potential use-after-free in TX ack timer teardown
      commit: d9be5e75530772fc31637070d51e5717d6aeaa2a

Best regards,
-- 
Jeff Johnson <jeff.johnson@oss.qualcomm.com>