Re: [PATCH v5.18] ath9k: Save rate counts before clearing tx status area

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

Hello Toke,

On Sat,  2 Apr 2022 14:27:51 +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, so
> we should restore them after clearing. However, we can get rid of the
> existing clearing of the counts of invalid rates. Rearrange the code a bit
> so the order fits the indexes, and so the setting of the count to
> hw->max_rate_tries on underrun is not immediately overridden.
> 
> 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 | 25 +++++++++++++++----------
>  1 file changed, 15 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
> index cbcf96ac303e..ac7efecff29c 100644
> --- a/drivers/net/wireless/ath/ath9k/xmit.c
> +++ b/drivers/net/wireless/ath/ath9k/xmit.c
> @@ -2551,16 +2551,19 @@ static void ath_tx_rc_status(struct ath_softc *sc, struct ath_buf *bf,
>  	struct ieee80211_tx_info *tx_info = IEEE80211_SKB_CB(skb);
>  	struct ieee80211_hw *hw = sc->hw;
>  	struct ath_hw *ah = sc->sc_ah;
> -	u8 i, tx_rateindex;
> +	u8 i, tx_rateindex, tries[IEEE80211_TX_MAX_RATES];
> +
> +	tx_rateindex = ts->ts_rateindex;
> +	WARN_ON(tx_rateindex >= hw->max_rates);
> +
> +	for (i = 0; i < tx_rateindex; i++)
> +		tries[i] = tx_info->status.rates[i].count;
>  
>  	ieee80211_tx_info_clear_status(tx_info);
>  
>  	if (txok)
>  		tx_info->status.ack_signal = ts->ts_rssi;
>  
> -	tx_rateindex = ts->ts_rateindex;
> -	WARN_ON(tx_rateindex >= hw->max_rates);
> -
>  	if (tx_info->flags & IEEE80211_TX_CTL_AMPDU) {
>  		tx_info->flags |= IEEE80211_TX_STAT_AMPDU;
>  
> @@ -2569,6 +2572,14 @@ 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;
>  
> +	for (i = 0; i < tx_rateindex; i++)
> +		tx_info->status.rates[i].count = tries[i];
> +
> +	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].idx = -1;
> +
>  	if ((ts->ts_status & ATH9K_TXERR_FILT) == 0 &&
>  	    (tx_info->flags & IEEE80211_TX_CTL_NO_ACK) == 0) {
>  		/*
> @@ -2591,12 +2602,6 @@ static void ath_tx_rc_status(struct ath_softc *sc, struct ath_buf *bf,
>  				hw->max_rate_tries;
>  	}

The full lines above read:

2597                 if (unlikely(ts->ts_flags & (ATH9K_TX_DATA_UNDERRUN |
2598                                              ATH9K_TX_DELIM_UNDERRUN)) &&
2599                     ieee80211_is_data(hdr->frame_control) && 
2600                     ah->tx_trig_level >= sc->sc_ah->config.max_txtrig_level     )
2601                         tx_info->status.rates[tx_rateindex].count =
2602                                 hw->max_rate_tries;
2603         }

So this patch fixes by drive-by a overwrite of tx_info->status.rates[tx_rateindex].count...

>  
> -	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)

Otherwise looks good ;-), would like to give a Reviewed-by/Tested-by but still
affected by the underlying ieee80211_tx_info status vs. rate_driver_data overwrite
as mentioned in the other thread (see [1])...

Regards,
Peter


[1] https://lore.kernel.org/linux-wireless/20220404130453.5ec6e045@gmx.net/