netdev - [PATCH AUTOSEL 4.19 20/25] ax88172a: fix information leak on short answers

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Date:   Fri, 22 Nov 2019 14:48:53 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Oliver Neukum <oneukum@...e.com>,
        syzbot+a8d4acdad35e6bbca308@...kaller.appspotmail.com,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, linux-usb@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 20/25] ax88172a: fix information leak on short answers

From: Oliver Neukum <oneukum@...e.com>

[ Upstream commit a9a51bd727d141a67b589f375fe69d0e54c4fe22 ]

If a malicious device gives a short MAC it can elicit up to
5 bytes of leaked memory out of the driver. We need to check for
ETH_ALEN instead.

Reported-by: syzbot+a8d4acdad35e6bbca308@...kaller.appspotmail.com
Signed-off-by: Oliver Neukum <oneukum@...e.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/usb/ax88172a.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/usb/ax88172a.c b/drivers/net/usb/ax88172a.c
index 501576f538546..914cac55a7ae7 100644
--- a/drivers/net/usb/ax88172a.c
+++ b/drivers/net/usb/ax88172a.c
@@ -208,7 +208,7 @@ static int ax88172a_bind(struct usbnet *dev, struct usb_interface *intf)
 
 	/* Get the MAC address */
 	ret = asix_read_cmd(dev, AX_CMD_READ_NODE_ID, 0, 0, ETH_ALEN, buf, 0);
-	if (ret < 0) {
+	if (ret < ETH_ALEN) {
 		netdev_err(dev->net, "Failed to read MAC address: %d\n", ret);
 		goto free;
 	}
-- 
2.20.1