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Message-ID: <6305.1275927536@localhost>
Date: Mon, 07 Jun 2010 12:18:56 -0400
From: Valdis.Kletnieks@...edu
To: Kees Cook <kees.cook@...onical.com>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>,
Dave Young <hidave.darkstar@...il.com>,
Al Viro <viro@...iv.linux.org.uk>,
Eric Paris <eparis@...hat.com>,
Christoph Hellwig <hch@...radead.org>,
James Morris <jmorris@...ei.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>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
David Howells <dhowells@...hat.com>,
Ingo Molnar <mingo@...e.hu>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Tim Gardner <tim.gardner@...onical.com>,
"Serge E. Hallyn" <serue@...ibm.com>, tytso@....edu,
Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH v6] fs: allow protected cross-uid sticky symlinks
(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@...onical.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@...ssion.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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