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

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 <redacted>
Signed-off-by: Song Li <redacted>
Signed-off-by: Fan Wu <redacted>
---
 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);