linux-kernel - Re: Linux 3.6

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Message-ID: <20121003235834.GA29174@thunk.org>
Date:	Wed, 3 Oct 2012 19:58:34 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Matthias Schniedermeyer <ms@...d.de>
Cc:	Kees Cook <kees@...flux.net>,
	Nick Bowler <nbowler@...iptictech.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 3.6

On Thu, Oct 04, 2012 at 12:23:41AM +0200, Matthias Schniedermeyer wrote:
> Personally i would have been bitten by this change, because for years i 
> have used a symlink in /tmp (which has the sticky bit) to a directory 
> somewhere else for historical reasons. But as i was aware of this change 
> i fixed my system before booting the new kernel.

As long as you own the symlink, it wouldn't be a problem.  The problem
comes when the symlink is owned by some user such as
"untrusted_daemon", which could change where the symlink could point
at any any time --- or could create a new symlink where none had
previously existed in some world-writeable directory such as /tmp.

Now you try to use that symlink, assuming that it points to *foo*,
when in fact it now points to *bar*, and hilarity ensues...

						- Ted
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