[PATCH] net: usb: smsc95xx: Limit packet length to skb->len

[Szymon Heidrich]

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@xxxxxxxxx>
---
 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