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

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Message-ID: <20120323064748.GA8029@moon>
Date:	Fri, 23 Mar 2012 10:47:48 +0400
From:	Cyrill Gorcunov <gorcunov@...nvz.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	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 Fri, Mar 23, 2012 at 10:41:36AM +0400, Cyrill Gorcunov wrote:
> On Thu, Mar 22, 2012 at 04:38:43PM -0700, Eric W. Biederman wrote:
> > >
> > > Andrew, take a look please, will the changelog and comments look
> > > better?
> > 
> > Can you change this to take an actual address and get the exe_file
> > from an mmapped area and make certain that the mmaped_area is already
> > mapped MAP_EXEC.
> > 
> > That will prevent out-right lies.
> > 
> > At least then we will know that exe_file will at least be a file that is
> > mapped executable in the process's address space.  It's not a lot better
> > but it makes /proc/<pid>/exe at almost as trustable as it is now.
> 
> This won't work for all cases. When we restore a program we map new
> VM_EXEC areas _without_ vma::vm_file field.
> 

Well, it's not complete true ;) At moment all exec areas we re-map during
restore do correspond to executable files. but I think having ability to
set this symlink without requirement such as 'every VM_EXEC should be
mapped with file' is a win. That said I would prefer to leave this interface
as is, until there strong objections.

	Cyrill
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