To: a1426z@gawab.com
CC: torvalds@osdl.org, linuxram@us.ibm.com, viro@ftp.linux.org.uk,
       linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
       rob@landley.net
In-reply-to: <200511160835.28636.a1426z@gawab.com> (message from Al Boldi on
	Wed, 16 Nov 2005 08:35:28 +0300)
Subject: Re: [PATCH 12/18] shared mount handling: bind and rbind
References: <E1EZInj-0001Ez-AV@ZenIV.linux.org.uk> <200511152129.04079.rob@landley.net> <Pine.LNX.4.64.0511151948570.13959@g5.osdl.org> <200511160835.28636.a1426z@gawab.com>
Message-Id: <E1EcIVw-0005ZH-00@dorka.pomaz.szeredi.hu>
From: Miklos Szeredi <miklos@szeredi.hu>
Date: Wed, 16 Nov 2005 09:19:32 +0100
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 912
Lines: 22

> > This is why we have "pivot_root()" and "chroot()", which can both be used
> > to do what you want to do. You mount the new root somewhere else, and then
> > you chroot (or pivot-root) to it. And THEN you do 'chdir("/")' to move the
> > cwd into the new root too (and only at that point have you "lost" the old
> > root - although you can actually get it back if you have some file
> > descriptor open to it).
> 
> Wouldn't this constitute a security flaw?
> 
> Shouldn't chroot jail you?

No, chroot should just change the root.

If you don't want to be able to get back the old root, just close all
file descriptors _in addition_ to chroot() and chdir().

Miklos
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