linux-kernel - [PATCH AUTOSEL 4.4 33/43] rndis_wlan: potential buffer overflow in rndis_wlan_auth

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Message-ID: <20180917030445.484-33-alexander.levin@microsoft.com>
Date:   Mon, 17 Sep 2018 03:05:09 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Dan Carpenter <dan.carpenter@...cle.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL 4.4 33/43] rndis_wlan: potential buffer overflow in
 rndis_wlan_auth_indication()

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>
---
 drivers/net/wireless/rndis_wlan.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/wireless/rndis_wlan.c b/drivers/net/wireless/rndis_wlan.c
index 259590013382..c76e0cfbb8b4 100644
--- a/drivers/net/wireless/rndis_wlan.c
+++ b/drivers/net/wireless/rndis_wlan.c
@@ -2919,6 +2919,8 @@ static void rndis_wlan_auth_indication(struct usbnet *usbdev,
 
 	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;
-- 
2.17.1