mac80211: check ERP info IE length in parser

It's always just one byte, so check for that and
remove the length field from the parser struct.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/ieee80211_i.h

@@ -1189,7 +1189,6 @@ struct ieee802_11_elems {
 	u8 tim_len;
 	u8 challenge_len;
 	u8 rsn_len;
-	u8 erp_info_len;
 	u8 ext_supp_rates_len;
 	u8 wmm_info_len;
 	u8 wmm_param_len;

net/mac80211/mlme.c

@@ -3038,7 +3038,7 @@ ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
 		changed |= BSS_CHANGED_DTIM_PERIOD;
 	}
 
-	if (elems.erp_info && elems.erp_info_len >= 1) {
+	if (elems.erp_info) {
 		erp_valid = true;
 		erp_value = elems.erp_info[0];
 	} else {

net/mac80211/scan.c

@@ -98,9 +98,8 @@ ieee80211_bss_info_update(struct ieee80211_local *local,
 	}
 
 	/* save the ERP value so that it is available at association time */
-	if (elems->erp_info && elems->erp_info_len >= 1 &&
-			(!elems->parse_error ||
-			 !(bss->valid_data & IEEE80211_BSS_VALID_ERP))) {
+	if (elems->erp_info && (!elems->parse_error ||
+				!(bss->valid_data & IEEE80211_BSS_VALID_ERP))) {
 		bss->erp_value = elems->erp_info[0];
 		bss->has_erp_value = true;
 		if (!elems->parse_error)

net/mac80211/util.c

@@ -780,8 +780,10 @@ u32 ieee802_11_parse_elems_crc(u8 *start, size_t len,
 			elems->rsn_len = elen;
 			break;
 		case WLAN_EID_ERP_INFO:
-			elems->erp_info = pos;
-			elems->erp_info_len = elen;
+			if (elen >= 1)
+				elems->erp_info = pos;
+			else
+				elem_parse_failed = true;
 			break;
 		case WLAN_EID_EXT_SUPP_RATES:
 			elems->ext_supp_rates = pos;