Re: [PATCH for-5.18 v2] ath9k: Fix usage of driver-private space in tx_info

[Peter Seiderer <ps.report@gmx.net>]

Hello Toke,

On Mon,  4 Apr 2022 20:11:51 +0200, Toke Høiland-Jørgensen <toke@toke.dk> wrote:

> From: Toke Høiland-Jørgensen <toke@redhat.com>
> 
> The ieee80211_tx_info_clear_status() helper also clears the rate counts and
> the driver-private part of struct ieee80211_tx_info, so using it breaks
> quite a few other things. So back out of using it, and instead define a
> ath-internal helper that only clears the area between the
> status_driver_data and the rates info. Combined with moving the
> ath_frame_info struct to status_driver_data, this avoids clearing anything
> we shouldn't be, and so we can keep the existing code for handling the rate
> information.
> 
> While fixing this I also noticed that the setting of
> tx_info->status.rates[tx_rateindex].count on hardware underrun errors was
> always immediately overridden by the normal setting of the same fields, so
> rearrange the code so that the underrun detection actually takes effect.
> 
> The new helper could be generalised to a 'memset_between()' helper, but
> leave it as a driver-internal helper for now since this needs to go to
> stable.
> 
> Cc: stable@vger.kernel.org
> Reported-by: Peter Seiderer <ps.report@gmx.net>
> Fixes: 037250f0a45c ("ath9k: Properly clear TX status area before reporting to mac80211")
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> ---
>  drivers/net/wireless/ath/ath9k/xmit.c | 30 ++++++++++++++++++---------
>  1 file changed, 20 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
> index cbcf96ac303e..db83cc4ba810 100644
> --- a/drivers/net/wireless/ath/ath9k/xmit.c
> +++ b/drivers/net/wireless/ath/ath9k/xmit.c
> @@ -141,8 +141,8 @@ static struct ath_frame_info *get_frame_info(struct sk_buff *skb)
>  {
>  	struct ieee80211_tx_info *tx_info = IEEE80211_SKB_CB(skb);
>  	BUILD_BUG_ON(sizeof(struct ath_frame_info) >
> -		     sizeof(tx_info->rate_driver_data));
> -	return (struct ath_frame_info *) &tx_info->rate_driver_data[0];
> +		     sizeof(tx_info->status.status_driver_data));
> +	return (struct ath_frame_info *) &tx_info->status.status_driver_data[0];
>  }

Would be too easy if all locations would use get_frame_info()..., at least one location
in drivers/net/wireless/ath/ath9k/main.c uses direct access:

 841                 txinfo = IEEE80211_SKB_CB(bf->bf_mpdu);
 842                 fi = (struct ath_frame_info *)&txinfo->rate_driver_data[0];
 843                 if (fi->keyix == keyix)
 844                         return true;

Regards,
Peter


>  
>  static void ath_send_bar(struct ath_atx_tid *tid, u16 seqno)
> @@ -2542,6 +2542,16 @@ static void ath_tx_complete_buf(struct ath_softc *sc, struct ath_buf *bf,
>  	spin_unlock_irqrestore(&sc->tx.txbuflock, flags);
>  }
>  
> +static void ath_clear_tx_status(struct ieee80211_tx_info *tx_info)
> +{
> +	void *ptr = &tx_info->status;
> +
> +	memset(ptr + sizeof(tx_info->status.rates), 0,
> +	       sizeof(tx_info->status) -
> +	       sizeof(tx_info->status.rates) -
> +	       sizeof(tx_info->status.status_driver_data));
> +}
> +
>  static void ath_tx_rc_status(struct ath_softc *sc, struct ath_buf *bf,
>  			     struct ath_tx_status *ts, int nframes, int nbad,
>  			     int txok)
> @@ -2553,7 +2563,7 @@ static void ath_tx_rc_status(struct ath_softc *sc, struct ath_buf *bf,
>  	struct ath_hw *ah = sc->sc_ah;
>  	u8 i, tx_rateindex;
>  
> -	ieee80211_tx_info_clear_status(tx_info);
> +	ath_clear_tx_status(tx_info);
>  
>  	if (txok)
>  		tx_info->status.ack_signal = ts->ts_rssi;
> @@ -2569,6 +2579,13 @@ static void ath_tx_rc_status(struct ath_softc *sc, struct ath_buf *bf,
>  	tx_info->status.ampdu_len = nframes;
>  	tx_info->status.ampdu_ack_len = nframes - nbad;
>  
> +	tx_info->status.rates[tx_rateindex].count = ts->ts_longretry + 1;
> +
> +	for (i = tx_rateindex + 1; i < hw->max_rates; i++) {
> +		tx_info->status.rates[i].count = 0;
> +		tx_info->status.rates[i].idx = -1;
> +	}
> +
>  	if ((ts->ts_status & ATH9K_TXERR_FILT) == 0 &&
>  	    (tx_info->flags & IEEE80211_TX_CTL_NO_ACK) == 0) {
>  		/*
> @@ -2590,13 +2607,6 @@ static void ath_tx_rc_status(struct ath_softc *sc, struct ath_buf *bf,
>  			tx_info->status.rates[tx_rateindex].count =
>  				hw->max_rate_tries;
>  	}
> -
> -	for (i = tx_rateindex + 1; i < hw->max_rates; i++) {
> -		tx_info->status.rates[i].count = 0;
> -		tx_info->status.rates[i].idx = -1;
> -	}
> -
> -	tx_info->status.rates[tx_rateindex].count = ts->ts_longretry + 1;
>  }
>  
>  static void ath_tx_processq(struct ath_softc *sc, struct ath_txq *txq)