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SubjectRe: [PATCH v6] fs: allow protected cross-uid sticky symlinks
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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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