From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH v2012.1] fs: symlink restrictions on sticky directories
Date: Fri, 6 Jan 2012 08:34:56 +0100
Message-ID: <20120106073456.GB14188@elte.hu>
References: <20120104201800.GA2587@www.outflux.net>
 <20120105143008.GA31728@elliptictech.com>
 <CAGXu5jLYhxOK8u-H8mhTvHBzvkRi8d-=zTeginjukDMEFri-0Q@mail.gmail.com>
 <20120105200810.GA3826@elliptictech.com>
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 <4F065704.4020306@redhat.com>
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Cc: Kees Cook <keescook@chromium.org>,
	Nick Bowler <nbowler@elliptictech.com>,
	linux-kernel@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Andrew Morton <akpm@linux-foundation.org>,
	Federica Teodori <federica.teodori@googlemail.com>,
	Lucian Adrian Grijincu <lucian.grijincu@gmail.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Eric Paris <eparis@redhat.com>,
	Randy Dunlap <rdunlap@xenotime.net>,
	Dan Rosenberg <drosenberg@vsecurity.com>,
	linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	kernel-hardening@lists.openwall.com
To: Rik van Riel <riel@redhat.com>
Return-path: <linux-doc-owner@vger.kernel.org>
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* Rik van Riel <riel@redhat.com> wrote:

> On 01/05/2012 03:55 PM, Kees Cook wrote:
> >On Thu, Jan 5, 2012 at 12:08 PM, Nick Bowler<nbowler@elliptictech.com>  wrote:
> 
> >>But this is a brand new feature that changes longstanding behaviour of
> >>various syscalls.  Making it default to enabled is rather mean to users
> >>(since it will tend to get enabled by "oldconfig") and seems almost
> >>guaranteed to cause regressions.
> >
> > I couldn't disagree more. There has been zero evidence of 
> > this change causing anything but regressions in _attacks_. 
> > :P If anything, I think there should be no CONFIG and no 
> > sysctl, and it should be entirely non-optional. But since 
> > this patch needs consensus, I have provided knobs to control 
> > it.
> 
> I agree with you, Kees.
> 
> The behaviour introduced by this patch should produce so few 
> issues, that the new behaviour should probably be on by 
> default.

Up to the point people report regressions.

And yes, I think Kees is perfectly right that the setting of the 
default should be evidence based. (Assuming Al and Linus is fine 
with the whole concept.)

The only specific counter-argument I can see is the spinlock 
performance impact I raised during review. I think we can (and 
should) live with that, and it's probably fixable, BYMMV.

Thanks,

	Ingo