linux-kernel - [PATCH][-next] rtlwifi: kfree entry until after entry->bssid has been accessed

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Message-Id: <20170630100843.9188-1-colin.king@canonical.com>
Date:   Fri, 30 Jun 2017 11:08:43 +0100
From:   Colin King <colin.king@...onical.com>
To:     Larry Finger <Larry.Finger@...inger.net>,
        Chaoming Li <chaoming_li@...lsil.com.cn>,
        Kalle Valo <kvalo@...eaurora.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][-next] rtlwifi: kfree entry until after entry->bssid has been accessed

From: Colin Ian King <colin.king@...onical.com>

The current code kfree's entry and then dereferences it by accessing
entry->bssid.  Avoid the dereference-after-free by moving the kfree
after the access to entry->bssid.

Detected by CoverityScan, CID#1448600 ("Read from pointer after free")

Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/net/wireless/realtek/rtlwifi/base.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/realtek/rtlwifi/base.c b/drivers/net/wireless/realtek/rtlwifi/base.c
index e36ee592c660..208f56297a75 100644
--- a/drivers/net/wireless/realtek/rtlwifi/base.c
+++ b/drivers/net/wireless/realtek/rtlwifi/base.c
@@ -1735,12 +1735,12 @@ void rtl_scan_list_expire(struct ieee80211_hw *hw)
 			continue;
 
 		list_del(&entry->list);
-		kfree(entry);
 		rtlpriv->scan_list.num--;
 
 		RT_TRACE(rtlpriv, COMP_SCAN, DBG_LOUD,
 			 "BSSID=%pM is expire in scan list (total=%d)\n",
 			 entry->bssid, rtlpriv->scan_list.num);
+		kfree(entry);
 	}
 
 	spin_unlock_irqrestore(&rtlpriv->locks.scan_list_lock, flags);
-- 
2.11.0