linux-kernel - [PATCH 4.4 033/113] rndis_wlan: potential buffer overflow in rndis_wlan_auth

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Date:   Mon,  8 Oct 2018 20:30:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.4 033/113] rndis_wlan: potential buffer overflow in rndis_wlan_auth_indication()

4.4-stable review patch.  If anyone has any objections, please let me know.

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

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

[ Upstream commit ae636fb1554833ee5133ca47bf4b2791b6739c52 ]

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@...cle.com>
Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 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
@@ -2919,6 +2919,8 @@ 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;