linux-kernel - [PATCH 4.4 19/92] mwifiex: fix potential NULL dereference and use after free

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Message-Id: <20191204174330.808228957@linuxfoundation.org>
Date:   Wed,  4 Dec 2019 18:49:19 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Pan Bian <bianpan2016@....com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 19/92] mwifiex: fix potential NULL dereference and use after free

From: Pan Bian <bianpan2016@....com>

[ Upstream commit 1dcd9429212b98bea87fc6ec92fb50bf5953eb47 ]

There are two defects: (1) passing a NULL bss to
mwifiex_save_hidden_ssid_channels will result in NULL dereference,
(2) using bss after dropping the reference to it via cfg80211_put_bss.
To fix them, the patch moves the buggy code to the branch that bss is
not NULL and puts it before cfg80211_put_bss.

Signed-off-by: Pan Bian <bianpan2016@....com>
Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/wireless/mwifiex/scan.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/net/wireless/mwifiex/scan.c b/drivers/net/wireless/mwifiex/scan.c
index b3fa3e4bed052..39b78dc1bd92b 100644
--- a/drivers/net/wireless/mwifiex/scan.c
+++ b/drivers/net/wireless/mwifiex/scan.c
@@ -1873,15 +1873,17 @@ mwifiex_parse_single_response_buf(struct mwifiex_private *priv, u8 **bss_info,
 					    ETH_ALEN))
 					mwifiex_update_curr_bss_params(priv,
 								       bss);
-				cfg80211_put_bss(priv->wdev.wiphy, bss);
-			}
 
-			if ((chan->flags & IEEE80211_CHAN_RADAR) ||
-			    (chan->flags & IEEE80211_CHAN_NO_IR)) {
-				mwifiex_dbg(adapter, INFO,
-					    "radar or passive channel %d\n",
-					    channel);
-				mwifiex_save_hidden_ssid_channels(priv, bss);
+				if ((chan->flags & IEEE80211_CHAN_RADAR) ||
+				    (chan->flags & IEEE80211_CHAN_NO_IR)) {
+					mwifiex_dbg(adapter, INFO,
+						    "radar or passive channel %d\n",
+						    channel);
+					mwifiex_save_hidden_ssid_channels(priv,
+									  bss);
+				}
+
+				cfg80211_put_bss(priv->wdev.wiphy, bss);
 			}
 		}
 	} else {
-- 
2.20.1