hv_netvsc: Restrict configurations on isolated guests

Restrict the NVSP protocol version(s) that will be negotiated with the
host to be NVSP_PROTOCOL_VERSION_61 or greater if the guest is running
isolated.  Moreover, do not advertise the SR-IOV capability and ignore
NVSP_MSG_4_TYPE_SEND_VF_ASSOCIATION messages in isolated guests, which
are not supposed to support SR-IOV.  This reduces the footprint of the
code that will be exercised by Confidential VMs and hence the exposure
to bugs and vulnerabilities.
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20210201144814.2701-5-parri.andrea@gmail.comSigned-off-by: Wei Liu <wei.liu@kernel.org>

drivers/net/hyperv/netvsc.c

@@ -22,6 +22,7 @@
 #include <linux/prefetch.h>
 
 #include <asm/sync_bitops.h>
+#include <asm/mshyperv.h>
 
 #include "hyperv_net.h"
 #include "netvsc_trace.h"
@@ -544,6 +545,9 @@ static int negotiate_nvsp_ver(struct hv_device *device,
 	init_packet->msg.v2_msg.send_ndis_config.capability.ieee8021q = 1;
 
 	if (nvsp_ver >= NVSP_PROTOCOL_VERSION_5) {
+		if (hv_is_isolation_supported())
+			netdev_info(ndev, "SR-IOV not advertised by guests on the host supporting isolation\n");
+		else
 			init_packet->msg.v2_msg.send_ndis_config.capability.sriov = 1;
 
 		/* Teaming bit is needed to receive link speed updates */
@@ -591,6 +595,13 @@ static int netvsc_connect_vsp(struct hv_device *device,
 		goto cleanup;
 	}
 
+	if (hv_is_isolation_supported() && net_device->nvsp_version < NVSP_PROTOCOL_VERSION_61) {
+		netdev_err(ndev, "Invalid NVSP version 0x%x (expected >= 0x%x) from the host supporting isolation\n",
+			   net_device->nvsp_version, NVSP_PROTOCOL_VERSION_61);
+		ret = -EPROTO;
+		goto cleanup;
+	}
+
 	pr_debug("Negotiated NVSP version:%x\n", net_device->nvsp_version);
 
 	/* Send the ndis version */
@@ -1357,6 +1368,9 @@ static void netvsc_receive_inband(struct net_device *ndev,
 		break;
 
 	case NVSP_MSG4_TYPE_SEND_VF_ASSOCIATION:
+		if (hv_is_isolation_supported())
+			netdev_err(ndev, "Ignore VF_ASSOCIATION msg from the host supporting isolation\n");
+		else
 			netvsc_send_vf(ndev, nvmsg, msglen);
 		break;
 	}