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

[Jeff Johnson]

On 2/6/2026 10:52 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@xxxxxxxxxxxxxxx
> Signed-off-by: Daniel Hodges <git@xxxxxxxxxxxxxxxx>
> ---
>  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);

My review agent claims this still doesn't fix the UAF since aggr_timeout() can
call mod_timer() to rearm itself and hence the timer can fire again.
Instead it suggests timer_shutdown_sync() should be used since that prevents
any rearm from taking effect.

But I'm not familiar with this driver so I don't know if there are reasons to
not use timer_shutdown_sync(), i.e. if the timer will be reused again then
timer_setup() will need to be called again.

>  		aggr_conn->timer_scheduled = false;
>  	}
>