linux-kernel - Re: [PATCH v2] fs: block cross-uid sticky symlinks

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Date:	Tue, 1 Jun 2010 03:55:29 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Kees Cook <kees.cook@...onical.com>
Cc:	James Morris <jmorris@...ei.org>,
	Christoph Hellwig <hch@...radead.org>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
	Randy Dunlap <rdunlap@...otime.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>,
	Dave Young <hidave.darkstar@...il.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Eric Paris <eparis@...hat.com>,
	David Howells <dhowells@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Tim Gardner <tim.gardner@...onical.com>,
	"Serge E. Hallyn" <serue@...ibm.com>
Subject: Re: [PATCH v2] fs: block cross-uid sticky symlinks

On Mon, May 31, 2010 at 08:24:23PM -0700, Kees Cook wrote:
> Well, that's what I'm trying to understand.  It sounds like there is some
> general agreement that the issue needs to be solved, but some folks do not
> want it in the core VFS.  As in, the objections aren't with how symlink
> behavior is changed, just that the changes would be in the fs/ directory.

No, it's not.  It's not a change we can make for the default that
everyone uses.  If you're keen to mess up installations you control (aka
ubuntu valuedadd viper) push it into a special LSM or rather a
non-standard rule for it.  It really doesn't matter if it's in fs/ or
security/ but it's simplify not going to happen by default.

> My rationale is that if it's in commoncaps, it's effective for everyone, so
> it might as well be in core VFS.  If the VFS objections really do boil down
> to "not in fs/" then I'm curious if doing this in commoncaps is acceptable.

If you think the objection is about having things in fs/ you're smoking
some really bad stuff.

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