linux-kernel - Re: PING^7 (was Re: [PATCH v2 00/14] Corrections and customization of the SG

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Message-ID: <20130525124814.GA8489@mtj.dyndns.org>
Date:	Sat, 25 May 2013 21:48:14 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	James Bottomley <James.Bottomley@...senPartnership.com>,
	Jens Axboe <axboe@...nel.dk>,
	lkml <linux-kernel@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>
Subject: Re: PING^7 (was Re: [PATCH v2 00/14] Corrections and customization
 of the SG_IO command whitelist (CVE-2012-4542))

On Sat, May 25, 2013 at 01:14:37PM +0200, Paolo Bonzini wrote:
> > Don't think we can.  It'd be a behavior change clearly visible to
> > userland at this point.
> 
> We can (and even for MMC) if it is a build-time configuration knob.  It
> would satisfy those people who want the CVE fixed, as long as userspace
> gets some configurability.

I don't think that's a good idea.  We can gradually try to phase it
out by triggering warning message if SG_IO commands are issued to !MMC
devices but I'm not sure that'd be worth the effort.

> > * Merge the patch to give out SG_IO access along with write access, so
> >   the use cases which want to give out SG_IO access can do so
> >   explicitly and be fully responsible for the device.  This makes
> >   sense to me.  If one wants to be allowed to issue raw commands to
> >   the hardware, one takes the full responsibility.
> 
> That's not possible; it would make it impossible to do things like using
> a privileged helper to open the file and passing it back via SCM_RIGHTS
> to an unprivileged program (running as the user).  This is the ptrace
> attack that you mentioned.

I have no idea what you're talking about.  I'm describing the same
thing you implemented and posted.

-- 
tejun
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