hv_netvsc: Fix validation in netvsc_linkstatus_callback()

Contrary to the RNDIS protocol specification, certain (pre-Fe)
implementations of Hyper-V's vSwitch did not account for the status
buffer field in the length of an RNDIS packet; the bug was fixed in
newer implementations.  Validate the status buffer fields using the
length of the 'vmtransfer_page' packet (all implementations), that
is known/validated to be less than or equal to the receive section
size and not smaller than the length of the RNDIS message.
Reported-by: Dexuan Cui <decui@microsoft.com>
Suggested-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Fixes: 505e3f00 ("hv_netvsc: Add (more) validation for untrusted Hyper-V values")
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/hyperv_net.h

@@ -229,7 +229,7 @@ int netvsc_send(struct net_device *net,
 		bool xdp_tx);
 void netvsc_linkstatus_callback(struct net_device *net,
 				struct rndis_message *resp,
-				void *data);
+				void *data, u32 data_buflen);
 int netvsc_recv_callback(struct net_device *net,
 			 struct netvsc_device *nvdev,
 			 struct netvsc_channel *nvchan);

drivers/net/hyperv/netvsc_drv.c

@@ -744,7 +744,7 @@ static netdev_tx_t netvsc_start_xmit(struct sk_buff *skb,
  */
 void netvsc_linkstatus_callback(struct net_device *net,
 				struct rndis_message *resp,
-				void *data)
+				void *data, u32 data_buflen)
 {
 	struct rndis_indicate_status *indicate = &resp->msg.indicate_status;
 	struct net_device_context *ndev_ctx = netdev_priv(net);
@@ -765,11 +765,16 @@ void netvsc_linkstatus_callback(struct net_device *net,
 	if (indicate->status == RNDIS_STATUS_LINK_SPEED_CHANGE) {
 		u32 speed;
 
-		/* Validate status_buf_offset */
+		/* Validate status_buf_offset and status_buflen.
+		 *
+		 * Certain (pre-Fe) implementations of Hyper-V's vSwitch didn't account
+		 * for the status buffer field in resp->msg_len; perform the validation
+		 * using data_buflen (>= resp->msg_len).
+		 */
 		if (indicate->status_buflen < sizeof(speed) ||
 		    indicate->status_buf_offset < sizeof(*indicate) ||
-		    resp->msg_len - RNDIS_HEADER_SIZE < indicate->status_buf_offset ||
-		    resp->msg_len - RNDIS_HEADER_SIZE - indicate->status_buf_offset
+		    data_buflen - RNDIS_HEADER_SIZE < indicate->status_buf_offset ||
+		    data_buflen - RNDIS_HEADER_SIZE - indicate->status_buf_offset
 				< indicate->status_buflen) {
 			netdev_err(net, "invalid rndis_indicate_status packet\n");
 			return;

drivers/net/hyperv/rndis_filter.c

@@ -620,7 +620,7 @@ int rndis_filter_receive(struct net_device *ndev,
 
 	case RNDIS_MSG_INDICATE:
 		/* notification msgs */
-		netvsc_linkstatus_callback(ndev, rndis_msg, data);
+		netvsc_linkstatus_callback(ndev, rndis_msg, data, buflen);
 		break;
 	default:
 		netdev_err(ndev,