| Message ID | 20220402153014.31332-1-ps.report@gmx.net |
|---|---|
| State | New |
| Headers | show |
| Series | [v1,1/2] ath9k: fix ath_get_rate_txpower() to respect the rate list end tag | expand |
Peter Seiderer <ps.report@gmx.net> writes: > Stop reading (and copying) from ieee80211_tx_rate to ath_tx_info.rates > after list end tag (count == 0, idx < 0), prevents copying of garbage > to card registers. In the normal case I don't think this patch does anything, since any invalid rate entries will already be skipped (just one at a time instead of all at once). So this comment is a bit misleading. Also, Minstrel could in principle produce a rate sequence where the indexes are all positive, but there's one in the middle with a count of 0, couldn't it? With this patch, the last entries of such a sequence would now be skipped... -Toke
Hello Toke, On Mon, 04 Apr 2022 20:19:39 +0200, Toke Høiland-Jørgensen <toke@toke.dk> wrote: > Peter Seiderer <ps.report@gmx.net> writes: > > > Stop reading (and copying) from ieee80211_tx_rate to ath_tx_info.rates > > after list end tag (count == 0, idx < 0), prevents copying of garbage > > to card registers. > > In the normal case I don't think this patch does anything, since any > invalid rate entries will already be skipped (just one at a time instead > of all at once). So this comment is a bit misleading. Save some (minimal) compute time? Found it something misleading while debugging to see random values written out to the card and found this comment in net/mac80211/rate.c: 648 /* 649 * make sure there's no valid rate following 650 * an invalid one, just in case drivers don't 651 * take the API seriously to stop at -1. 652 */ and multiple places doing the same check (count == 0, idx < 0) for validation e.g.: 723 if (i < ARRAY_SIZE(info->control.rates) && 724 info->control.rates[i].idx >= 0 && 725 info->control.rates[i].count) { or 742 if (rates[i].idx < 0 || !rates[i].count) 743 break; > > Also, Minstrel could in principle produce a rate sequence where the > indexes are all positive, but there's one in the middle with a count of > 0, couldn't it? With this patch, the last entries of such a sequence > would now be skipped... According to net/mac80211/rc80211_minstrel_ht.c: 1128 static bool 1129 minstrel_ht_txstat_valid(struct minstrel_priv *mp, struct minstrel_ht_sta * mi, 1130 struct ieee80211_tx_rate *rate) 1131 { 1132 int i; 1133 1134 if (rate->idx < 0) 1135 return false; 1136 1137 if (!rate->count) 1138 return false; 1139 minstrel although evaluates a rate count of zero as invalid... Regards, Peter > > -Toke
Peter Seiderer <ps.report@gmx.net> writes: > Hello Toke, > > On Mon, 04 Apr 2022 20:19:39 +0200, Toke Høiland-Jørgensen <toke@toke.dk> wrote: > >> Peter Seiderer <ps.report@gmx.net> writes: >> >> > Stop reading (and copying) from ieee80211_tx_rate to ath_tx_info.rates >> > after list end tag (count == 0, idx < 0), prevents copying of garbage >> > to card registers. >> >> In the normal case I don't think this patch does anything, since any >> invalid rate entries will already be skipped (just one at a time instead >> of all at once). So this comment is a bit misleading. > > Save some (minimal) compute time? Found it something misleading while > debugging to see random values written out to the card and found this > comment in net/mac80211/rate.c: > > 648 /* > 649 * make sure there's no valid rate following > 650 * an invalid one, just in case drivers don't > 651 * take the API seriously to stop at -1. > 652 */ > > and multiple places doing the same check (count == 0, idx < 0) for validation > e.g.: > > 723 if (i < ARRAY_SIZE(info->control.rates) && > 724 info->control.rates[i].idx >= 0 && > 725 info->control.rates[i].count) { > > or > > 742 if (rates[i].idx < 0 || !rates[i].count) > 743 break; > >> >> Also, Minstrel could in principle produce a rate sequence where the >> indexes are all positive, but there's one in the middle with a count of >> 0, couldn't it? With this patch, the last entries of such a sequence >> would now be skipped... > > According to net/mac80211/rc80211_minstrel_ht.c: > > 1128 static bool > 1129 minstrel_ht_txstat_valid(struct minstrel_priv *mp, struct minstrel_ht_sta * mi, > 1130 struct ieee80211_tx_rate *rate) > 1131 { > 1132 int i; > 1133 > 1134 if (rate->idx < 0) > 1135 return false; > 1136 > 1137 if (!rate->count) > 1138 return false; > 1139 > > minstrel although evaluates a rate count of zero as invalid... So my concern was mostly that the documentation (in mac80211.h) says that an idx of -1 indicates the end, but says nothing about the count. Which implies that in principle you could have a rate table of { idx, count } like { 1, 1 }, { 2, 0 }, { 3, 1 } which would mean all three rates was valid but the second one would just be "skipped" due to a count of zero. But it seems that the code populating the rate table that you linked above (lines 742/743) actually do abort on either condition, so I guess it's safe to do so in the driver as well... -Toke
Peter Seiderer <ps.report@gmx.net> wrote: > Stop reading (and copying) from ieee80211_tx_rate to ath_tx_info.rates > after list end tag (count == 0, idx < 0), prevents copying of garbage > to card registers. > > Note: no need to write to the remaining ath_tx_info.rates entries > as the complete ath_tx_info struct is already initialized to zero from > both call sites. > > Signed-off-by: Peter Seiderer <ps.report@gmx.net> > Acked-by: Toke Høiland-Jørgensen <toke@toke.dk> > Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com> Patch applied to ath-next branch of ath.git, thanks. 24584d4f0afc ath9k: fix ath_get_rate_txpower() to respect the rate list end tag
diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c index d0caf1de2bde..ec9bad2d9510 100644 --- a/drivers/net/wireless/ath/ath9k/xmit.c +++ b/drivers/net/wireless/ath/ath9k/xmit.c @@ -1271,7 +1271,7 @@ static void ath_buf_set_rate(struct ath_softc *sc, struct ath_buf *bf, int phy; if (!rates[i].count || (rates[i].idx < 0)) - continue; + break; rix = rates[i].idx; info->rates[i].Tries = rates[i].count;
Stop reading (and copying) from ieee80211_tx_rate to ath_tx_info.rates after list end tag (count == 0, idx < 0), prevents copying of garbage to card registers. Note: no need to write to the remaining ath_tx_info.rates entries as the complete ath_tx_info struct is already initialized to zero from both call sites. Signed-off-by: Peter Seiderer <ps.report@gmx.net> --- drivers/net/wireless/ath/ath9k/xmit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)