From mboxrd@z Thu Jan  1 00:00:00 1970
From: Valdis.Kletnieks@vt.edu
Subject: Re: [PATCH v6] fs: allow protected cross-uid sticky symlinks
Date: Mon, 07 Jun 2010 12:18:56 -0400
Message-ID: <6305.1275927536@localhost>
References: <20100603080158.GE4971@outflux.net> <m11vcnlw9j.fsf@fess.ebiederm.org>
            <20100603210051.GD4714@outflux.net>
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Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
	Dave Young <hidave.darkstar@gmail.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Eric Paris <eparis@redhat.com>,
	Christoph Hellwig <hch@infradead.org>,
	James Morris <jmorris@namei.org>, linux-kernel@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org,
	Randy Dunlap <rdunlap@xenotime.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	Jiri Kosina <jkosina@suse.cz>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	David Howells <dhowells@redhat.com>,
	Ingo Molnar <mingo@elte.hu>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Tim Gardner <tim.gardner@canonical.com>,
	"Serge E. Hallyn" <serue@us.ibm.com>, tytso@mit.edu,
	Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Kees Cook <kees.cook@canonical.com>
Return-path: <linux-doc-owner@vger.kernel.org>
In-Reply-To: Your message of "Thu, 03 Jun 2010 14:00:51 PDT."
             <20100603210051.GD4714@outflux.net>
Sender: linux-doc-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org

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(Sorry for the late reply, didn't have time last few days to drink from the
lkml firehose)

On Thu, 03 Jun 2010 14:00:51 PDT, Kees Cook said:
> On Thu, Jun 03, 2010 at 01:02:48PM -0700, Eric W. Biederman wrote:
> > Kees Cook <kees.cook@canonical.com> writes:
> > > A long-standing class of security issues is the symlink-based
> > > time-of-check-time-of-use race, most commonly seen in world-writable
> > > directories like /tmp. The common method of exploitation of this flaw
> > 
> > Nacked-by: "Eric W. Biederman" <ebiederm@xmission.com>
> > 
> > This approach to fix the problem to of /tmp looks to me like it
> > will have the opposite effect.  I think this patch will encourage
> > more badly written applications.
> 
> How to safely deal with /tmp has been well understood for well over
> a decade.  I don't think this change would "encourage" poor code.

The fact that you're proposing this patch a decade after we "well understood"
the problem should suggest that it *will* encourage poor code, as the same
programmers who don't currently get it right (and are thus the targets of your
patch) will quite likely just say "Oh, I saw a patch for that, I don't have to
try to do it right..."


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