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Date: Fri, 23 Mar 2012 10:47:48 +0400
From: Cyrill Gorcunov <gorcunov@openvz.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        richard -rw- weinberger <richard.weinberger@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>, Oleg Nesterov <oleg@redhat.com>,
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        Pavel Emelyanov <xemul@parallels.com>,
        Kees Cook <keescook@chromium.org>, Tejun Heo <tj@kernel.org>,
        Matt Helsley <matthltc@us.ibm.com>
Subject: Re: [patch 1/2] c/r: prctl: Add ability to set new
 mm_struct::exe_file
Message-ID: <20120323064748.GA8029@moon>
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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