mac80211: fix a memory leak where sta_info is not freed

The following is from a system that went OOM due to a memory leak:

wlan0: Allocated STA 74:83:c2:64:0b:87
wlan0: Allocated STA 74:83:c2:64:0b:87
wlan0: IBSS finish 74:83:c2:64:0b:87 (---from ieee80211_ibss_add_sta)
wlan0: Adding new IBSS station 74:83:c2:64:0b:87
wlan0: moving STA 74:83:c2:64:0b:87 to state 2
wlan0: moving STA 74:83:c2:64:0b:87 to state 3
wlan0: Inserted STA 74:83:c2:64:0b:87
wlan0: IBSS finish 74:83:c2:64:0b:87 (---from ieee80211_ibss_work)
wlan0: Adding new IBSS station 74:83:c2:64:0b:87
wlan0: moving STA 74:83:c2:64:0b:87 to state 2
wlan0: moving STA 74:83:c2:64:0b:87 to state 3
.
.
wlan0: expiring inactive not authorized STA 74:83:c2:64:0b:87
wlan0: moving STA 74:83:c2:64:0b:87 to state 2
wlan0: moving STA 74:83:c2:64:0b:87 to state 1
wlan0: Removed STA 74:83:c2:64:0b:87
wlan0: Destroyed STA 74:83:c2:64:0b:87

The ieee80211_ibss_finish_sta() is called twice on the same STA from 2 different locations. On the second attempt, the allocated STA is not destroyed creating a kernel memory leak.

This is happening because sta_info_insert_finish() does not call sta_info_free() the second time when the STA already exists (returns -EEXIST). Note that the caller sta_info_insert_rcu() assumes STA is destroyed upon errors.

Same fix is applied to -ENOMEM.

---
 net/mac80211/sta_info.c | 2 ++
 1 file changed, 2 insertions(+)

index 2b5acb37587f..35fb885040b1 100644
@@ -640,12 +640,14 @@ static int sta_info_insert_finish(struct sta_info *sta) __acquires(RCU)
 
 	/* check if STA exists already */
 	if (sta_info_get_bss(sdata, sta->sta.addr)) {
+		sta_info_free(local, sta);
 		err = -EEXIST;
 		goto out_err;
 	}
 
 	sinfo = kzalloc(sizeof(struct station_info), GFP_KERNEL);
 	if (!sinfo) {
+		sta_info_free(local, sta);
 		err = -ENOMEM;
 		goto out_err;
 	}

2.25.1