From:   Szymon Heidrich <szymon.heidrich@gmail.com>
To:     steve.glendinning@shawell.net, UNGLinuxDriver@microchip.com,
        davem@davemloft.net, edumazet@google.com
Cc:     kuba@kernel.org, pabeni@redhat.com, szymon.heidrich@gmail.com,
        linux-usb@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] net: usb: smsc95xx: Limit packet length to skb->len
Date:   Mon, 13 Mar 2023 23:01:24 +0100
Message-Id: <20230313220124.52437-1-szymon.heidrich@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Packet length retrieved from skb data may be larger than
the actual socket buffer length (up to 1526 bytes). In such
case the cloned skb passed up the network stack will leak
kernel memory contents.

Fixes: 2f7ca802bdae ("net: Add SMSC LAN9500 USB2.0 10/100 ethernet adapter driver")
Signed-off-by: Szymon Heidrich <szymon.heidrich@gmail.com>
---
 drivers/net/usb/smsc95xx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index 32d2c60d3..ba766bdb2 100644
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -1851,7 +1851,8 @@ static int smsc95xx_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 			}
 		} else {
 			/* ETH_FRAME_LEN + 4(CRC) + 2(COE) + 4(Vlan) */
-			if (unlikely(size > (ETH_FRAME_LEN + 12))) {
+			if (unlikely(size > (ETH_FRAME_LEN + 12) ||
+				     size > skb->len)) {
 				netif_dbg(dev, rx_err, dev->net,
 					  "size err header=0x%08x\n", header);
 				return 0;
-- 
2.39.2