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

Packet length retrieved from descriptor may be larger than
the actual socket buffer length. In such case the cloned
skb passed up the network stack will leak kernel memory contents.

Fixes: 2f7ca802 ("net: Add SMSC LAN9500 USB2.0 10/100 ethernet adapter driver")
Signed-off-by: Szymon Heidrich <szymon.heidrich@gmail.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20230316101954.75836-1-szymon.heidrich@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/usb/smsc95xx.c

@@ -1833,6 +1833,12 @@ static int smsc95xx_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 		size = (u16)((header & RX_STS_FL_) >> 16);
 		align_count = (4 - ((size + NET_IP_ALIGN) % 4)) % 4;
 
+		if (unlikely(size > skb->len)) {
+			netif_dbg(dev, rx_err, dev->net,
+				  "size err header=0x%08x\n", header);
+			return 0;
+		}
+
 		if (unlikely(header & RX_STS_ES_)) {
 			netif_dbg(dev, rx_err, dev->net,
 				  "Error header=0x%08x\n", header);