Re: [PATCH] wifi: ath6kl: fix use-after-free in aggr_reset_state()

[Rameshkumar Sundaram <rameshkumar.sundaram@oss.qualcomm.com>]

On 2/7/2026 12:22 AM, Daniel Hodges wrote:
> The aggr_reset_state() function uses timer_delete() (non-synchronous)
> for the aggregation timer before proceeding to delete TID state and
> before the structure is freed by callers like aggr_module_destroy().
> 
> If the timer callback (aggr_timeout) is executing when aggr_reset_state()
> is called, the callback will continue to access aggr_conn fields like
> rx_tid[] and stat[] which may be freed immediately after by
> kfree(aggr_info->aggr_conn) in aggr_module_destroy().
> 
> Additionally, the timer callback can re-arm itself via mod_timer() while
> aggr_reset_state() is running, creating a more complex race condition.
> 
> Use timer_delete_sync() instead to ensure any running timer callback
> has completed before returning.
> 
> Fixes: bdcd81707973 ("Add ath6kl cleaned up driver")
> Cc: stable@vger.kernel.org
> Signed-off-by: Daniel Hodges <git@danielhodges.dev>
> ---
>   drivers/net/wireless/ath/ath6kl/txrx.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/ath/ath6kl/txrx.c b/drivers/net/wireless/ath/ath6kl/txrx.c
> index c3b06b515c4f..25ff5dec221c 100644
> --- a/drivers/net/wireless/ath/ath6kl/txrx.c
> +++ b/drivers/net/wireless/ath/ath6kl/txrx.c
> @@ -1828,7 +1828,7 @@ void aggr_reset_state(struct aggr_info_conn *aggr_conn)
>   		return;
>   
>   	if (aggr_conn->timer_scheduled) {
> -		timer_delete(&aggr_conn->timer);
> +		timer_delete_sync(&aggr_conn->timer);
>   		aggr_conn->timer_scheduled = false;
>   	}
>   

I am not familiar with ath6kl either, but while looking through the code,

aggr_reset_state() still calls timer_delete_sync() only when
aggr_conn->timer_scheduled is true. However aggr_timeout() clears
timer_scheduled near the beginning of the callback, before it walks
aggr_conn->rx_tid[] and updates aggr_conn->stat[].

So aggr_reset_state() can observe timer_scheduled == false while the
timer callback is still running, skip timer_delete_sync(), and then 
delete the TID state / allow aggr_conn to be freed. That still leaves 
the UAF window open.

I think timer_delete_sync() should be called unconditionally after the
aggr_conn NULL check, and timer_scheduled can then be cleared afterwards.


--
Ramesh