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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org,
        "Dan Carpenter" <dan.carpenter@oracle.com>,
        "Kalle Valo" <kvalo@codeaurora.org>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
Message-ID: <lsq.1544392233.171574999@decadent.org.uk>
Subject: [PATCH 3.16 010/328] rndis_wlan: potential buffer overflow in
 rndis_wlan_auth_indication()
In-Reply-To: <lsq.1544392232.713909046@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
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3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <dan.carpenter@oracle.com>

commit ae636fb1554833ee5133ca47bf4b2791b6739c52 upstream.

This is a static checker fix, not something I have tested.  The issue
is that on the second iteration through the loop, we jump forward by
le32_to_cpu(auth_req->length) bytes.  The problem is that if the length
is more than "buflen" then we end up with a negative "buflen".  A
negative buflen is type promoted to a high positive value and the loop
continues but it's accessing beyond the end of the buffer.

I believe the "auth_req->length" comes from the firmware and if the
firmware is malicious or buggy, you're already toasted so the impact of
this bug is probably not very severe.

Fixes: 030645aceb3d ("rndis_wlan: handle 802.11 indications from device")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/net/wireless/rndis_wlan.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/net/wireless/rndis_wlan.c
+++ b/drivers/net/wireless/rndis_wlan.c
@@ -2917,6 +2917,8 @@ static void rndis_wlan_auth_indication(s
 
 	while (buflen >= sizeof(*auth_req)) {
 		auth_req = (void *)buf;
+		if (buflen < le32_to_cpu(auth_req->length))
+			return;
 		type = "unknown";
 		flags = le32_to_cpu(auth_req->flags);
 		pairwise_error = false;