linux-kernel - [PATCH AUTOSEL 5.10 04/19] mac80211: fix a memory leak where sta

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Date:   Mon, 20 Dec 2021 20:58:59 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Ahmed Zaki <anzaki@...il.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Sasha Levin <sashal@...nel.org>, johannes@...solutions.net,
        davem@...emloft.net, kuba@...nel.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.10 04/19] mac80211: fix a memory leak where sta_info is not freed

From: Ahmed Zaki <anzaki@...il.com>

[ Upstream commit 8f9dcc29566626f683843ccac6113a12208315ca ]

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.

Signed-off-by: Ahmed Zaki <anzaki@...il.com>
Link: https://lore.kernel.org/r/20211002145329.3125293-1-anzaki@gmail.com
[change the error path label to use the existing code]
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/mac80211/sta_info.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index e18c3855f6161..461c03737da8d 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -645,13 +645,13 @@ 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)) {
 		err = -EEXIST;
-		goto out_err;
+		goto out_cleanup;
 	}

 	sinfo = kzalloc(sizeof(struct station_info), GFP_KERNEL);
 	if (!sinfo) {
 		err = -ENOMEM;
-		goto out_err;
+		goto out_cleanup;
 	}

 	local->num_sta++;
@@ -707,8 +707,8 @@ static int sta_info_insert_finish(struct sta_info *sta) __acquires(RCU)
  out_drop_sta:
 	local->num_sta--;
 	synchronize_net();
+ out_cleanup:
 	cleanup_single_sta(sta);
- out_err:
 	mutex_unlock(&local->sta_mtx);
 	kfree(sinfo);
 	rcu_read_lock();
-- 
2.34.1