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

[Michael Kelley <mikelley@microsoft.com>]

From: Andrea Parri (Microsoft) <parri.andrea@gmail.com> Sent: Tuesday, January 26, 2021 3:57 AM
> 
> 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");

Nit:  Flip the "if" and "else" clauses so that the ! isn't needed in the test.

> 
>  		/* 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])) {

Could this test go after the 'for' loop, like the test for i < 0?  That would
get the code unindented a lot.  And maybe the helper function logic
(i.e., nvsp_is_valid_version) could just be coded inline.

> +				netdev_err(ndev, "Invalid NVSP version 0x%x (expected >= 0x%x) from the host with isolation supported\n",

Nit: The other two new messages use the phrase "... the host supporting isolation".

> +					   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");

Nit:  Flip the "if" and "else" clauses so that the ! isn't needed in the test.

>  		break;
>  	}
>  }
> --
> 2.25.1