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

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Message-ID: <20120610191654.GE10523@redhat.com>
Date:	Sun, 10 Jun 2012 22:16:54 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	"Hans J. Koch" <hjk@...sjkoch.de>
Cc:	Alex Williamson <alex.williamson@...hat.com>,
	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 09:11:30PM +0200, Hans J. Koch wrote:
> On Sun, Jun 10, 2012 at 10:00:36PM +0300, Michael S. Tsirkin wrote:
> > 
> > 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.
> 
> You need to be root to access a UIO device, and if you're root, you can
> compromise a system in many ways. Before UIO, people used /dev/mem for
> similar purposes, and UIO is certainly a seccurity improvement over that.
> 
> But of course, UIO presents security risks. Like many other things below
> /dev, you need to know what you're doing, and who gets access to /dev/uioX.
> 
> Thanks,
> Hans

Sorry I might not have explained myself clearly.  uio_pci_generic would
be insecure if used with a device doing DMA. I am not speaking
about UIO in general at all.

-- 
MST
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