linux-kernel - Re: [patch 2/2] fs, proc: Introduce the /proc/<pid>/map

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Message-ID: <20110914111437.GA22516@atrey.karlin.mff.cuni.cz>
Date:	Wed, 14 Sep 2011 13:14:38 +0200
From:	Pavel Machek <pavel@....cz>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Andrew Morton <akpm00@...il.com>, linux-kernel@...r.kernel.org,
	containers@...ts.osdl.org, linux-fsdevel@...r.kernel.org,
	Kirill Shutemov <kirill@...temov.name>,
	Pavel Emelyanov <xemul@...allels.com>,
	James Bottomley <jbottomley@...allels.com>,
	Nathan Lynch <ntl@...ox.com>, Zan Lynx <zlynx@....org>,
	Daniel Lezcano <dlezcano@...ibm.com>,
	Vasiliy Kulikov <segoon@...nwall.com>,
	Tejun Heo <tj@...nel.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Al Viro <viro@...IV.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [patch 2/2] fs, proc: Introduce the /proc/<pid>/map_files/
	directory v12

Hi!

> > 
> > > This one behaves similarly to the /proc/<pid>/fd/ one - it contains symlinks
> > > one for each mapping with file, the name of a symlink is "vma->vm_start-vma->vm_end",
> > > the target is the file. Opening a symlink results in a file that point exactly
> > > to the same inode as them vma's one.
> > 
> > We should fully work through Pavel Machek's comments, please.  For some
> > reason I'm a bit paranoid about security lately :(
> 
> Pavel, I somehow lost. What exactly the security issue here? There are a few
> patches from Vasiliy in -mm queue at moment. In particular one includes
> .permission set for fd/ handling. So I've updated the map_files as well
> (it's below). So please review and point me where the problem
> is. Thanks!

AFAICT, this recreates existing problem with /proc/<pid>/fd (see
discussion at 

http://www.securityfocus.com/archive/1/507386/30/0/threaded

). It creates object that looks like symlink, but does not behave as
one, and permissions of directories are not checked as they would be
if it was a symlink.

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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