linux-kernel - Re: Chroot bug

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Message-ID: <Pine.LNX.4.64.0709251847570.945@fbirervta.pbzchgretzou.qr>
Date:	Tue, 25 Sep 2007 18:52:55 +0200 (CEST)
From:	Jan Engelhardt <jengelh@...putergmbh.de>
To:	Miloslav Semler <majkls@...pere.com>
cc:	serge@...lyn.com, davidsen@....com, philipp@...ek.priv.at,
	7eggert@....de, alan@...rguk.ukuu.org.uk,
	linux-kernel@...r.kernel.org
Subject: Re: Chroot bug


On Sep 25 2007 18:19, Miloslav Semler wrote:
>> > > So what? Just do this: chdir into the root after chroot.
>> > >       
>> > I don't think so.  His exploit just got me all the way out of a chroot
>> > within a
>> > chroot within a chroot, inclusive of lots of chdirs.
>> >     
>>
>> Close all fds that point to directories outside the root ;-)
>>   
> This  does not help.  Let's try:
> chroot somewhere
> mkdir foo
> fd = open /
> chroot foo

('fd' implicitly closed and chdir to /foo)

> fchdir fd

-EINVAL

> chdir ".."

/../ => /

> ....
> chdir ".."
> chroot "."
> so you are in root.

so we remain in chroot.
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