mac80211: fix last RX rate data consistency

When storing the last_rate_* values in the RX code, there's nothing
to guarantee consistency, so a concurrent reader could see, e.g.
last_rate_idx on the new value, but last_rate_flag still on the old,
getting completely bogus values in the end.

To fix this, I lifted the sta_stats_encode_rate() function from my
old rate statistics code, which encodes the entire rate data into a
single 16-bit value, avoiding the consistency issue.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 32 insertions, 28 deletions

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index ac73b9c7e8d8..0b50ae3f0b05 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -1928,43 +1928,47 @@ u8 sta_info_tx_streams(struct sta_info *sta)
 			>> IEEE80211_HT_MCS_TX_MAX_STREAMS_SHIFT) + 1;
 }
 
-static void sta_set_rate_info_rx(struct sta_info *sta, struct rate_info *rinfo)
+static void sta_stats_decode_rate(struct ieee80211_local *local, u16 rate,
+				  struct rate_info *rinfo)
 {
-	rinfo->flags = 0;
-
-	if (sta->rx_stats.last_rate_flag & RX_FLAG_HT) {
-		rinfo->flags |= RATE_INFO_FLAGS_MCS;
-		rinfo->mcs = sta->rx_stats.last_rate_idx;
-	} else if (sta->rx_stats.last_rate_flag & RX_FLAG_VHT) {
-		rinfo->flags |= RATE_INFO_FLAGS_VHT_MCS;
-		rinfo->nss = sta->rx_stats.last_rate_vht_nss;
-		rinfo->mcs = sta->rx_stats.last_rate_idx;
-	} else {
+	rinfo->bw = (rate & STA_STATS_RATE_BW_MASK) >>
+		STA_STATS_RATE_BW_SHIFT;
+
+	if (rate & STA_STATS_RATE_VHT) {
+		rinfo->flags = RATE_INFO_FLAGS_VHT_MCS;
+		rinfo->mcs = rate & 0xf;
+		rinfo->nss = (rate & 0xf0) >> 4;
+	} else if (rate & STA_STATS_RATE_HT) {
+		rinfo->flags = RATE_INFO_FLAGS_MCS;
+		rinfo->mcs = rate & 0xff;
+	} else if (rate & STA_STATS_RATE_LEGACY) {
 		struct ieee80211_supported_band *sband;
-		int shift = ieee80211_vif_get_shift(&sta->sdata->vif);
 		u16 brate;
-
-		sband = sta->local->hw.wiphy->bands[
-				ieee80211_get_sdata_band(sta->sdata)];
-		brate = sband->bitrates[sta->rx_stats.last_rate_idx].bitrate;
+		unsigned int shift;
+
+		sband = local->hw.wiphy->bands[(rate >> 4) & 0xf];
+		brate = sband->bitrates[rate & 0xf].bitrate;
+		if (rinfo->bw == RATE_INFO_BW_5)
+			shift = 2;
+		else if (rinfo->bw == RATE_INFO_BW_10)
+			shift = 1;
+		else
+			shift = 0;
 		rinfo->legacy = DIV_ROUND_UP(brate, 1 << shift);
 	}
 
-	if (sta->rx_stats.last_rate_flag & RX_FLAG_SHORT_GI)
+	if (rate & STA_STATS_RATE_SGI)
 		rinfo->flags |= RATE_INFO_FLAGS_SHORT_GI;
+}
+
+static void sta_set_rate_info_rx(struct sta_info *sta, struct rate_info *rinfo)
+{
+	u16 rate = ACCESS_ONCE(sta->rx_stats.last_rate);
 
-	if (sta->rx_stats.last_rate_flag & RX_FLAG_5MHZ)
-		rinfo->bw = RATE_INFO_BW_5;
-	else if (sta->rx_stats.last_rate_flag & RX_FLAG_10MHZ)
-		rinfo->bw = RATE_INFO_BW_10;
-	else if (sta->rx_stats.last_rate_flag & RX_FLAG_40MHZ)
-		rinfo->bw = RATE_INFO_BW_40;
-	else if (sta->rx_stats.last_rate_vht_flag & RX_VHT_FLAG_80MHZ)
-		rinfo->bw = RATE_INFO_BW_80;
-	else if (sta->rx_stats.last_rate_vht_flag & RX_VHT_FLAG_160MHZ)
-		rinfo->bw = RATE_INFO_BW_160;
+	if (rate == STA_STATS_RATE_INVALID)
+		rinfo->flags = 0;
 	else
-		rinfo->bw = RATE_INFO_BW_20;
+		sta_stats_decode_rate(sta->local, rate, rinfo);
 }
 
 void sta_set_sinfo(struct sta_info *sta, struct station_info *sinfo)