[PATCH net] rndis_host: Check for integer overflows in rndis_rx_fixup()

[Dan Carpenter]

The "data_offset" and "data_len" values come from received skb->data so
we don't trust them.  They are u32 types. Check that the "data_offset +
data_len + 8" addition does not have an integer overflow.

Fixes: 64e049102d3d ("[PATCH] USB: usbnet (8/9) module for RNDIS devices")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
---
 drivers/net/usb/rndis_host.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/usb/rndis_host.c b/drivers/net/usb/rndis_host.c
index 7b3739b29c8f..913aca6ff434 100644
--- a/drivers/net/usb/rndis_host.c
+++ b/drivers/net/usb/rndis_host.c
@@ -513,8 +513,9 @@ int rndis_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 		data_len = le32_to_cpu(hdr->data_len);
 
 		/* don't choke if we see oob, per-packet data, etc */
-		if (unlikely(msg_type != RNDIS_MSG_PACKET || skb->len < msg_len
-				|| (data_offset + data_len + 8) > msg_len)) {
+		if (unlikely(msg_type != RNDIS_MSG_PACKET || skb->len < msg_len ||
+				size_add(data_offset, data_len) > U32_MAX - 8 ||
+				(data_offset + data_len + 8) > msg_len)) {
 			dev->net->stats.rx_frame_errors++;
 			netdev_dbg(dev->net, "bad rndis message %d/%d/%d/%d, len %d\n",
 				   le32_to_cpu(hdr->msg_type),
-- 
2.51.0