linux-kernel - RE: [PATCH v3 hyperv-next 3/4] Drivers: hv: vmbus: Enforce 'VMBus version >= 5.2' on isolated guests

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Date:   Mon, 1 Feb 2021 17:47:39 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     "Andrea Parri (Microsoft)" <parri.andrea@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        Saruhan Karademir <skarade@...rosoft.com>,
        Juan Vazquez <juvazq@...rosoft.com>
Subject: RE: [PATCH v3 hyperv-next 3/4] Drivers: hv: vmbus: Enforce 'VMBus
 version >= 5.2' on isolated guests

From: Andrea Parri (Microsoft) <parri.andrea@...il.com> Sent: Monday, February 1, 2021 6:48 AM
> 
> Restrict the protocol version(s) that will be negotiated with the host
> to be 5.2 or greater if the guest is running isolated.  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@...il.com>
> ---
>  drivers/hv/connection.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index 11170d9a2e1a5..c83612cddb995 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -244,6 +244,13 @@ int vmbus_connect(void)
>  			break;
>  	}
> 
> +	if (hv_is_isolation_supported() && version < VERSION_WIN10_V5_2) {
> +		pr_err("Invalid VMBus version %d.%d (expected >= %d.%d) from the host supporting isolation\n",
> +		       version >> 16, version & 0xFFFF, VERSION_WIN10_V5_2 >> 16, VERSION_WIN10_V5_2 & 0xFFFF);
> +		ret = -EINVAL;
> +		goto cleanup;
> +	}
> +
>  	vmbus_proto_version = version;
>  	pr_info("Vmbus version:%d.%d\n",
>  		version >> 16, version & 0xFFFF);
> --
> 2.25.1

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>