linux-kernel - Re: [patch] x64, fpu: fix possible FPU leakage in error conditions

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Message-ID: <alpine.LFD.1.10.0807241154260.3237@nehalem.linux-foundation.org>
Date:	Thu, 24 Jul 2008 11:59:03 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
cc:	"x86@...nel.org" <x86@...nel.org>,
	"andi@...stfloor.org" <andi@...stfloor.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"stable@...nel.org" <stable@...nel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [patch] x64, fpu: fix possible FPU leakage in error conditions



On Thu, 24 Jul 2008, Suresh Siddha wrote:
> 
> If we don't do init_fpu() + restore from the sane init state, process has
> to be killed, in the paranoid failing scenario of math_state_restore()

Umm. I'm still not seeing why the right answer is not just to do "stts + 
math_used = 0". 

And the specific case of math_state_restore(), that will also fix the 
problem - next time around.

As far as I can tell, your patch causes serious problems in case 
init_fpu() fails. Which it can do, afaik.

			Linus
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