cfg80211: fix a crash in nl80211_send_station

mac80211 leaves sinfo->assoc_req_ies uninitialized, causing a random
pointer memory access in nl80211_send_station.
Instead of checking if the pointer is null, use sinfo->filled, like
the rest of the fields.
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/net/cfg80211.h

@@ -421,6 +421,7 @@ struct station_parameters {
  * @STATION_INFO_RX_BITRATE: @rxrate fields are filled
  * @STATION_INFO_BSS_PARAM: @bss_param filled
  * @STATION_INFO_CONNECTED_TIME: @connected_time filled
+ * @STATION_INFO_ASSOC_REQ_IES: @assoc_req_ies filled
  */
 enum station_info_flags {
 	STATION_INFO_INACTIVE_TIME	= 1<<0,
@@ -439,7 +440,8 @@ enum station_info_flags {
 	STATION_INFO_SIGNAL_AVG		= 1<<13,
 	STATION_INFO_RX_BITRATE		= 1<<14,
 	STATION_INFO_BSS_PARAM          = 1<<15,
-	STATION_INFO_CONNECTED_TIME	= 1<<16
+	STATION_INFO_CONNECTED_TIME	= 1<<16,
+	STATION_INFO_ASSOC_REQ_IES	= 1<<17
 };
 
 /**

net/wireless/nl80211.c

@@ -2236,7 +2236,7 @@ static int nl80211_send_station(struct sk_buff *msg, u32 pid, u32 seq,
 	}
 	nla_nest_end(msg, sinfoattr);
 
-	if (sinfo->assoc_req_ies)
+	if (sinfo->filled & STATION_INFO_ASSOC_REQ_IES)
 		NLA_PUT(msg, NL80211_ATTR_IE, sinfo->assoc_req_ies_len,
 			sinfo->assoc_req_ies);