linux-kernel - Re: [PATCH 2/2] pci: allow sysfs file owner to read device dependent config space

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Date:	Thu, 13 May 2010 12:02:52 +0100
From:	"Daniel P. Berrange" <berrange@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Chris Wright <chrisw@...s-sol.org>, greg@...ah.com,
	jbarnes@...tuousgeek.org, matthew@....cx,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, ddutile@...hat.com, alex.williamson@...hat.com
Subject: Re: [PATCH 2/2] pci: allow sysfs file owner to read device dependent config space

On Thu, May 13, 2010 at 01:56:53PM +0300, Avi Kivity wrote:
> On 05/13/2010 04:29 AM, Chris Wright wrote:
> >The PCI config space bin_attr read handler has a hardcoded CAP_SYS_ADMIN
> >check to verify privileges before allowing a user to read device
> >dependent config space.  This is meant to protect from an unprivileged
> >user potentially locking up the box.
> >
> >When assigning a PCI device directly to a guest with libvirt and KVM,
> >the sysfs config space file is chown'd to the unprivileged user that
> >the KVM guest will run as.  The guest needs to have full access to the
> >device's config space since it's responsible for driving the device.
> >However, despite being the owner of the sysfs file, the CAP_SYS_ADMIN
> >check will not allow read access beyond the config header.
> >
> >With this patch the sysfs file owner is also considered privileged enough
> >to read all of the config space.
> >
> >   
> 
> Related questions:
> 
> - does sysfs support selinux labels?

With a recent enough kernel + selinux policy it does.

Regards,
Daniel
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