nl80211: Fix possible Spectre-v1 for NL80211_TXRATE_HT

Use array_index_nospec() to sanitize ridx with respect to speculation.
Signed-off-by: NMasashi Honma <masashi.honma@gmail.com>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

net/wireless/nl80211.c

@@ -3756,6 +3756,7 @@ static bool ht_rateset_to_mask(struct ieee80211_supported_band *sband,
 			return false;
 
 		/* check availability */
+		ridx = array_index_nospec(ridx, IEEE80211_HT_MCS_MASK_LEN);
 		if (sband->ht_cap.mcs.rx_mask[ridx] & rbit)
 			mcs[ridx] |= rbit;
 		else