linux-kernel - Re: 2.6.18 - check for chroot, broken root and cwd values in procfs

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Date:	Fri, 13 Oct 2006 21:02:50 -0600
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Bastian Blank <bastian@...di.eu.org>
Cc:	linux-kernel@...r.kernel.org, Andrew Morton <akpm@...l.org>,
	Linus Torvalds <torvalds@...l.org>
Subject: Re: 2.6.18 - check for chroot, broken root and cwd values in procfs

Bastian Blank <bastian@...di.eu.org> writes:

> On Thu, Oct 12, 2006 at 04:02:24PM +0200, Bastian Blank wrote:
>> The commit 778c1144771f0064b6f51bee865cceb0d996f2f9 replaced the old
>> root-based security checks in procfs with processed based ones.
>
> The new behaviour even allows a user to escape from the chroot by using
> chdir to /proc/$pid/cwd or /proc/$pid/root of a process he owns and
> lives outside of the chroot.

Yep.  It makes it obvious that you can do that.

If you were in a chroot you could always ptrace a process you own
that was outside of the chroot, and cause it to do things, such as
open a unix domain socket and pass you it's current root directory.

chroot by itself has never been much of a jail.

Eric
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