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From:   Colin King <colin.king@canonical.com>
To:     Kalle Valo <kvalo@codeaurora.org>,
        "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Ping-Ke Shih <pkshih@realtek.com>,
        linux-wireless@vger.kernel.org, netdev@vger.kernel.org
Cc:     kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH][next] rtw89: Fix potential dereference of the null pointer sta
Date:   Fri, 15 Oct 2021 16:45:30 +0100
Message-Id: <20211015154530.34356-1-colin.king@canonical.com>
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From: Colin Ian King <colin.king@canonical.com>

The pointer rtwsta is dereferencing pointer sta before sta is
being null checked, so there is a potential null pointer deference
issue that may occur. Fix this by only assigning rtwsta after sta
has been null checked. Add in a null pointer check on rtwsta before
dereferencing it too.

Fixes: e3ec7017f6a2 ("rtw89: add Realtek 802.11ax driver")
Addresses-Coverity: ("Dereference before null check")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/net/wireless/realtek/rtw89/core.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtw89/core.c b/drivers/net/wireless/realtek/rtw89/core.c
index 06fb6e5b1b37..26f52a25f545 100644
--- a/drivers/net/wireless/realtek/rtw89/core.c
+++ b/drivers/net/wireless/realtek/rtw89/core.c
@@ -1534,9 +1534,14 @@ static bool rtw89_core_txq_agg_wait(struct rtw89_dev *rtwdev,
 {
 	struct rtw89_txq *rtwtxq = (struct rtw89_txq *)txq->drv_priv;
 	struct ieee80211_sta *sta = txq->sta;
-	struct rtw89_sta *rtwsta = (struct rtw89_sta *)sta->drv_priv;
+	struct rtw89_sta *rtwsta;
 
-	if (!sta || rtwsta->max_agg_wait <= 0)
+	if (!sta)
+		return false;
+	rtwsta = (struct rtw89_sta *)sta->drv_priv;
+	if (!rtwsta)
+		return false;
+	if (rtwsta->max_agg_wait <= 0)
 		return false;
 
 	if (rtwdev->stats.tx_tfc_lv <= RTW89_TFC_MID)
-- 
2.32.0