linux-kernel - Re: [patch 1/2] c/r: prctl: Add ability to set new mm_struct::exe

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Date:	Tue, 20 Mar 2012 02:50:20 +0400
From:	Cyrill Gorcunov <gorcunov@...nvz.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	richard -rw- weinberger <richard.weinberger@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Kees Cook <keescook@...omium.org>, Tejun Heo <tj@...nel.org>,
	Matt Helsley <matthltc@...ibm.com>
Subject: Re: [patch 1/2] c/r: prctl: Add ability to set new
 mm_struct::exe_file

On Mon, Mar 19, 2012 at 03:46:49PM -0700, Andrew Morton wrote:
> 
> Please send a patch with the updated changelog and improved comment?

Sure I'll resend.

> 
> > >
> > > Actually I liked multi-shot version more but Matt arguments convinced
> > > me that one-short fashion is more "secure" in terms of overall kernel
> > > state and potential transitions/changes of this /proc/pid/exe symlink.
> > >
> > > At least with one-shot version the admin may be sure that the symlink
> > > is never changed more than once, ever.
> > >
> > 
> > And changing it once does not harm security?
> > I'm sure that rootkit writers will like this feature...
> 
> Well, let's discuss this more completely.  In what ways could an
> attacker use this?  How serious is the problem?  What actions can be
> taken to lessen it?  etcetera.

It can use it iif CAP_SYS_RESOURCE is granted.
Otherwise you'll get -eaccess.

	Cyrill
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