Re: [PATCH v2 4/6] virtio: Initialize authorized attribute for confidential guest - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Dan Williams <dan.j.williams@intel.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	Kuppuswamy Sathyanarayanan 
	<sathyanarayanan.kuppuswamy@linux.intel.com>,
	Borislav Petkov <bp@alien8.de>, X86 ML <x86@kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Andreas Noever <andreas.noever@gmail.com>,
	Michael Jamet <michael.jamet@intel.com>,
	Yehezkel Bernat <YehezkelShB@gmail.com>,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Jason Wang <jasowang@redhat.com>, Andi Kleen <ak@linux.intel.com>,
	Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux PCI <linux-pci@vger.kernel.org>,
	USB list <linux-usb@vger.kernel.org>,
	virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v2 4/6] virtio: Initialize authorized attribute for confidential guest
Date: Thu, 30 Sep 2021 15:49:35 +0200	[thread overview]
Message-ID: <YVXAb4C51e/L2sGv@kroah.com> (raw)
In-Reply-To: <CAPcyv4hP6mtzKS-CVb-aKf-kYuiLM771PMxN2zeBEfoj6NbctA@mail.gmail.com>

On Thu, Sep 30, 2021 at 06:36:18AM -0700, Dan Williams wrote:
> On Thu, Sep 30, 2021 at 4:03 AM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Wed, Sep 29, 2021 at 06:05:09PM -0700, Kuppuswamy Sathyanarayanan wrote:
> > > Confidential guest platforms like TDX have a requirement to allow
> > > only trusted devices. By default the confidential-guest core will
> > > arrange for all devices to default to unauthorized (via
> > > dev_default_authorization) in device_initialize(). Since virtio
> > > driver is already hardened against the attack from the un-trusted host,
> > > override the confidential computing default unauthorized state
> > >
> > > Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> > > Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> >
> > Architecturally this all looks backwards. IIUC nothing about virtio
> > makes it authorized or trusted. The driver is hardened,
> > true, but this should be set at the driver not the device level.
> 
> That's was my initial reaction to this proposal as well, and I ended
> up leading Sathya astray from what Greg wanted. Greg rightly points
> out that the "authorized" attribute from USB and Thunderbolt already
> exists [1] [2]. So the choice is find an awkward way to mix driver
> trust with existing bus-local "authorized" mechanisms, or promote the
> authorized capability to the driver-core. This patch set implements
> the latter to keep the momentum on the already shipping design scheme
> to not add to the driver-core maintenance burden.
> 
> [1]: https://lore.kernel.org/all/YQuaJ78y8j1UmBoz@kroah.com/
> [2]: https://lore.kernel.org/all/YQzF%2FutgrJfbZuHh@kroah.com/
> 
> > 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?

Please define "audited" and "trusted" here.

thanks,

greg k-h