iwlwifi: mvm: rs: fix a potential out of bounds access

Klocwork pointed these out. There is a theoretical possibility
that rate->index might be set to IWL_RATE_INVALID (15).
This could trigger an out of bounds access on ht_vht_rates or
legacy_rates arrays. Fix it by adding some checks.
Signed-off-by: Eyal Shapira <eyalx.shapira@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/rs.c

@@ -552,9 +552,10 @@ static char *rs_pretty_rate(const struct rs_rate *rate)
 	};
 	const char *rate_str;
 
-	if (is_type_legacy(rate->type))
+	if (is_type_legacy(rate->type) && (rate->index <= IWL_RATE_54M_INDEX))
 		rate_str = legacy_rates[rate->index];
-	else if (is_type_ht(rate->type) || is_type_vht(rate->type))
+	else if ((is_type_ht(rate->type) || is_type_vht(rate->type)) &&
+		 (rate->index <= IWL_RATE_MCS_9_INDEX))
 		rate_str = ht_vht_rates[rate->index];
 	else
 		rate_str = "BAD_RATE";