[PATCH v2 4/4] hv_netvsc: Restrict configurations on isolated guests

["Andrea Parri (Microsoft)" <parri.andrea@gmail.com>]

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>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
---
 drivers/net/hyperv/netvsc.c | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 1510a236aa341..afd92b4aa21fe 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/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"
@@ -544,7 +545,10 @@ 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) {
-		init_packet->msg.v2_msg.send_ndis_config.capability.sriov = 1;
+		if (!hv_is_isolation_supported())
+			init_packet->msg.v2_msg.send_ndis_config.capability.sriov = 1;
+		else
+			netdev_info(ndev, "SR-IOV not advertised by guests on the host supporting isolation\n");
 
 		/* Teaming bit is needed to receive link speed updates */
 		init_packet->msg.v2_msg.send_ndis_config.capability.teaming = 1;
@@ -563,6 +567,13 @@ static int negotiate_nvsp_ver(struct hv_device *device,
 	return ret;
 }
 
+static bool nvsp_is_valid_version(u32 version)
+{
+       if (hv_is_isolation_supported())
+               return version >= NVSP_PROTOCOL_VERSION_61;
+       return true;
+}
+
 static int netvsc_connect_vsp(struct hv_device *device,
 			      struct netvsc_device *net_device,
 			      const struct netvsc_device_info *device_info)
@@ -579,12 +590,19 @@ static int netvsc_connect_vsp(struct hv_device *device,
 	init_packet = &net_device->channel_init_pkt;
 
 	/* Negotiate the latest NVSP protocol supported */
-	for (i = ARRAY_SIZE(ver_list) - 1; i >= 0; i--)
+	for (i = ARRAY_SIZE(ver_list) - 1; i >= 0; i--) {
 		if (negotiate_nvsp_ver(device, net_device, init_packet,
 				       ver_list[i])  == 0) {
+			if (!nvsp_is_valid_version(ver_list[i])) {
+				netdev_err(ndev, "Invalid NVSP version 0x%x (expected >= 0x%x) from the host with isolation supported\n",
+					   ver_list[i], NVSP_PROTOCOL_VERSION_61);
+				ret = -EPROTO;
+				goto cleanup;
+			}
 			net_device->nvsp_version = ver_list[i];
 			break;
 		}
+	}
 
 	if (i < 0) {
 		ret = -EPROTO;
@@ -1357,7 +1375,10 @@ static void netvsc_receive_inband(struct net_device *ndev,
 		break;
 
 	case NVSP_MSG4_TYPE_SEND_VF_ASSOCIATION:
-		netvsc_send_vf(ndev, nvmsg, msglen);
+		if (!hv_is_isolation_supported())
+			netvsc_send_vf(ndev, nvmsg, msglen);
+		else
+			netdev_err(ndev, "Ignore VF_ASSOCIATION msg from the host supporting isolation\n");
 		break;
 	}
 }
-- 
2.25.1