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Date: Fri, 6 Jan 2012 08:34:56 +0100
From: Ingo Molnar <>
To: Rik van Riel <>
Cc: Kees Cook <>,
	Nick Bowler <>,,
	Alexander Viro <>,
	Andrew Morton <>,
	Federica Teodori <>,
	Lucian Adrian Grijincu <>,
	Peter Zijlstra <>,
	Eric Paris <>, Randy Dunlap <>,
	Dan Rosenberg <>,,,
Subject: Re: [PATCH v2012.1] fs: symlink restrictions on sticky directories

* Rik van Riel <> wrote:

> On 01/05/2012 03:55 PM, Kees Cook wrote:
> >On Thu, Jan 5, 2012 at 12:08 PM, Nick Bowler<>  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.



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