linux-kernel - Re: [PATCH] uio_pci_generic does not export memory resources

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20120610190036.GD10523@redhat.com>
Date:	Sun, 10 Jun 2012 22:00:36 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	"Hans J. Koch" <hjk@...sjkoch.de>,
	Andreas Hartmann <andihartmann@...19freenet.de>,
	Dominic Eschweiler <eschweiler@...s.uni-frankfurt.de>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] uio_pci_generic does not export memory resources

On Sun, Jun 10, 2012 at 11:38:25AM -0600, Alex Williamson wrote:
> On Sun, 2012-06-10 at 19:44 +0300, Michael S. Tsirkin wrote:
> > On Sun, Jun 10, 2012 at 10:09:26AM -0600, Alex Williamson wrote:
> > > On Sun, 2012-06-10 at 17:18 +0300, Michael S. Tsirkin wrote:
> > > > On Fri, Jun 08, 2012 at 11:11:16AM -0600, Alex Williamson wrote:
> > > > > On Fri, 2012-06-08 at 18:44 +0200, Hans J. Koch wrote:
> > > > > > On Fri, Jun 08, 2012 at 06:16:18PM +0200, Andreas Hartmann wrote:
> > > > > > > Hi Dominic,
> > > > > > > 
> > > > > > > Dominic Eschweiler wrote:
> > > > > > > > Am Freitag, den 08.06.2012, 08:16 -0600 schrieb Alex Williamson:
> > > > > > > >> Yes, thanks Jan.  This is exactly what VFIO does.  VFIO provides
> > > > > > > >> secure config space access, resource access, DMA mapping services, and
> > > > > > > >> full interrupt support to userspace.  
> > > > > > 
> > > > > > VFIO is not a "better UIO". It *requires* an IOMMU. Dominic didn't say on
> > > > > > what CPU he's working, so it's not clear if he can use VFIO at all.
> > > > > > 
> > > > > > UIO is intended for general use with devices that have mappable registers
> > > > > > and don't fit into any other subsystem. No more, no less.
> > > > > 
> > > > > VFIO is a secure UIO.
> > > > 
> > > > A secure UIO *for VFs*. I think that's why it's called VFIO :).
> > > > Other stuff sometimes also works but no real guarantees, though
> > > > VFIO tries to make sure you don't burn yourself too badly
> > > > if it breaks.
> > > 
> > > We do a little better than that.  Multifunction devices that don't
> > > explicitly report ACS support are grouped together, so we have security
> > > for multifunction devices as well.
> > 
> > How can you get security with insecure hardware?
> > 
> > So you prevent the device from writing to host memory? Cool.
> > Now guest puts a virus on an on-card flash, the
> > moment device is assigned to another VM it will own that,
> > or host if it's enabled in host.
> > 
> > I can make up more silliness.  Buggy userspace can brick the device,
> > e.g. by damaging the internal eeprom memory, and these things were known
> > to happen even by accident.
> > 
> > Simply put if you want secure userspace drivers you must be able to
> > trust your hardware for security and the only hardware that promises you
> > security is a VF in an SRIOV device.

One thing I stand corrected on: assigning a PF that does DMA with VFIO
*might* be secure, and sometimes, maybe often, is.
There's just no way to make sure.
This is unlike uio_pci_generic where it would always be insecure.

-- 
MST
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/