mac80211: minstrel: fix tx status processing corner case

BugLink: https://bugs.launchpad.net/bugs/1908561

commit b2911a8 upstream.

Some drivers fill the status rate list without setting the rate index after
the final rate to -1. minstrel_ht already deals with this, but minstrel
doesn't, which causes it to get stuck at the lowest rate on these drivers.

Fix this by checking the count as well.

Cc: [email protected]
Fixes: cccf129 ("mac80211: add the 'minstrel' rate control algorithm")
Signed-off-by: Felix Fietkau <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Johannes Berg <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Kamal Mostafa <[email protected]>
Signed-off-by: Ian May <[email protected]>

Author: nbd168

net/mac80211/rc80211_minstrel.c

@@ -270,7 +270,7 @@ minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
 	success = !!(info->flags & IEEE80211_TX_STAT_ACK);
 
 	for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
-		if (ar[i].idx < 0)
+		if (ar[i].idx < 0 || !ar[i].count)
 			break;
 
 		ndx = rix_to_ndx(mi, ar[i].idx);