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

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Message-ID: <20120319224746.GK19594@moon>
Date:	Tue, 20 Mar 2012 02:47:46 +0400
From:	Cyrill Gorcunov <gorcunov@...nvz.org>
To:	richard -rw- weinberger <richard.weinberger@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	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 11:41:36PM +0100, richard -rw- weinberger wrote:
> >
> > 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...

The one-shot limits the amount of transitions, but you still
have to obtain CAP_SYS_RESOURCE before you'll be able to change
this symlink (ie it's not 'anyone-can-change-it' feature).

	Cyrill
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