linux-kernel - Re: [PATCH v2 4/6] virtio: Initialize authorized attribute for confidential guest

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Date:   Thu, 30 Sep 2021 12:04:05 -0700
From:   "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <YehezkelShB@...il.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Jonathan Corbet <corbet@....net>,
        Jason Wang <jasowang@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        USB list <linux-usb@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v2 4/6] virtio: Initialize authorized attribute for
 confidential guest

On 9/30/21 8:23 AM, Greg Kroah-Hartman wrote:
> On Thu, Sep 30, 2021 at 08:18:18AM -0700, Kuppuswamy, Sathyanarayanan wrote:
>>
>>
>> On 9/30/21 6:36 AM, Dan Williams wrote:
>>>> And in particular, not all virtio drivers are hardened -
>>>> I think at this point blk and scsi drivers have been hardened - so
>>>> treating them all the same looks wrong.
>>> My understanding was that they have been audited, Sathya?
>>
>> Yes, AFAIK, it has been audited. Andi also submitted some patches
>> related to it. Andi, can you confirm.
> 
> What is the official definition of "audited"?

In our case (Confidential Computing platform), the host is an un-trusted
entity. So any interaction with host from the drivers will have to be
protected against the possible attack from the host. For example, if we
are accessing a memory based on index value received from host, we have
to make sure it does not lead to out of bound access or when sharing the
memory with the host, we need to make sure only the required region is
shared with the host and the memory is un-shared after use properly.

Elena can share more details, but it was achieved with static analysis
and fuzzing. Here is a presentation she is sharing about the work at the
Linux Security Summit:
https://static.sched.com/hosted_files/lssna2021/b6/LSS-HardeningLinuxGuestForCCC.pdf

Andi, can talk more about the specific driver changes that came out of this
effort.

In our case the driver is considered "hardened" / "audited" if it can handle
the above scenarios.

> 
> thanks,
> 
> greg k-h
> 

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer