mac80211: fix legacy and invalid rx-rate report

This fixes obtaining the rate info via sta_set_sinfo
when the rx rate is invalid (for instance, on IBSS
interface that has received no frames from one of its
peers).

Also initialize rinfo->flags for legacy rates, to not
rely on the whole sinfo being initialized to zero.
Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/sta_info.c

@@ -1972,6 +1972,7 @@ static void sta_stats_decode_rate(struct ieee80211_local *local, u16 rate,
 		u16 brate;
 		unsigned int shift;
 
+		rinfo->flags = 0;
 		sband = local->hw.wiphy->bands[(rate >> 4) & 0xf];
 		brate = sband->bitrates[rate & 0xf].bitrate;
 		if (rinfo->bw == RATE_INFO_BW_5)
@@ -1987,14 +1988,15 @@ static void sta_stats_decode_rate(struct ieee80211_local *local, u16 rate,
 		rinfo->flags |= RATE_INFO_FLAGS_SHORT_GI;
 }
 
-static void sta_set_rate_info_rx(struct sta_info *sta, struct rate_info *rinfo)
+static int sta_set_rate_info_rx(struct sta_info *sta, struct rate_info *rinfo)
 {
 	u16 rate = ACCESS_ONCE(sta_get_last_rx_stats(sta)->last_rate);
 
 	if (rate == STA_STATS_RATE_INVALID)
-		rinfo->flags = 0;
-	else
+		return -EINVAL;
+
 	sta_stats_decode_rate(sta->local, rate, rinfo);
+	return 0;
 }
 
 static void sta_set_tidstats(struct sta_info *sta,
@@ -2199,7 +2201,7 @@ void sta_set_sinfo(struct sta_info *sta, struct station_info *sinfo)
 	}
 
 	if (!(sinfo->filled & BIT(NL80211_STA_INFO_RX_BITRATE))) {
-		sta_set_rate_info_rx(sta, &sinfo->rxrate);
+		if (sta_set_rate_info_rx(sta, &sinfo->rxrate) == 0)
 			sinfo->filled |= BIT(NL80211_STA_INFO_RX_BITRATE);
 	}