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

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Message-ID: <20100513105911.6469c434@lxorguk.ukuu.org.uk>
Date:	Thu, 13 May 2010 10:59:11 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Chris Wright <chrisw@...s-sol.org>
Cc:	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 Wed, 12 May 2010 18:29:57 -0700
Chris Wright <chrisw@...s-sol.org> 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.

Or hacking it. You could argue the correct requirement is to change it to
require CAP_SYS_RAWIO in fact !

> With this patch the sysfs file owner is also considered privileged enough
> to read all of the config space.

Which breaks the main reason the check was there in the first place. To
stop accidents of the form

	find / -exec grep {} "wibble"

blowing up in people's faces.


I agree with the problem - but IMHO the fix is to require opening the file
checks CAP_SYS_something instead: not to hack the read method and make it
even weirder and more un-Linux than it is now.

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