linux-kernel - Re: [PATCH] futex: futex_find_get_task make credentials check conditional

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Message-ID: <alpine.LFD.2.00.1006291950420.2480@localhost.localdomain>
Date:	Tue, 29 Jun 2010 20:03:54 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Darren Hart <dvhltc@...ibm.com>
cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...e.de>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	Peter Zijlstra <peterz@...radead.org>,
	Jakub Jelinek <jakub@...hat.com>
Subject: Re: [PATCH] futex: futex_find_get_task make credentials check
 conditional

On Tue, 29 Jun 2010, Darren Hart wrote:
> On 06/29/2010 09:41 AM, Linus Torvalds wrote:
> > 
> > The other thing I'd like to see is to move the whole cred checking up
> > a level. There's no reason to check the credentials in
> > futex_find_get_task() that I can see - why not do it in the caller
> > instead? IOW, I think futex_find_get_task() should just look something
> > like this instead:
> 
> 
> /me beats head on desk, duh. Still, I'm hoping this isn't necessary and we can
> lose the credentials checking entirely.

I did some archaeology in my mail and code archives.

The only hint I found from the early days of the PI futex code is a
mail which mutters something about pid reuse. The euid/uid check
surfaced in the code archive right after that, but to be honest I fail
to see how it should be related. I rather believe that the whole thing
resulted out of being overly paranoid about the PI usage.

Jakub, any idea why this check got there ?

Today I cannot see a real reason to keep that check, it just adds a
restriction for no benefit.

Thanks,

	tglx
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