mac80211: check DSSS params 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/ibss.c

@@ -463,7 +463,7 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
 	struct ieee80211_supported_band *sband = local->hw.wiphy->bands[band];
 	bool rates_updated = false;
 
-	if (elems->ds_params && elems->ds_params_len == 1)
+	if (elems->ds_params)
 		freq = ieee80211_channel_to_frequency(elems->ds_params[0],
 						      band);
 	else

net/mac80211/ieee80211_i.h

@@ -1186,7 +1186,6 @@ struct ieee802_11_elems {
 	/* length of them, respectively */
 	u8 ssid_len;
 	u8 supp_rates_len;
-	u8 ds_params_len;
 	u8 tim_len;
 	u8 challenge_len;
 	u8 rsn_len;

net/mac80211/mesh.c

@@ -907,7 +907,7 @@ static void ieee80211_mesh_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
 	    (!elems.rsn && sdata->u.mesh.security != IEEE80211_MESH_SEC_NONE))
 		return;
 
-	if (elems.ds_params && elems.ds_params_len == 1)
+	if (elems.ds_params)
 		freq = ieee80211_channel_to_frequency(elems.ds_params[0], band);
 	else
 		freq = rx_status->freq;

net/mac80211/mlme.c

@@ -2695,7 +2695,7 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
 		}
 	}
 
-	if (elems->ds_params && elems->ds_params_len == 1)
+	if (elems->ds_params)
 		freq = ieee80211_channel_to_frequency(elems->ds_params[0],
 						      rx_status->band);
 	else

net/mac80211/util.c

@@ -739,8 +739,10 @@ u32 ieee802_11_parse_elems_crc(u8 *start, size_t len,
 			elems->supp_rates_len = elen;
 			break;
 		case WLAN_EID_DS_PARAMS:
-			elems->ds_params = pos;
-			elems->ds_params_len = elen;
+			if (elen >= 1)
+				elems->ds_params = pos;
+			else
+				elem_parse_failed = true;
 			break;
 		case WLAN_EID_TIM:
 			if (elen >= sizeof(struct ieee80211_tim_ie)) {