linux-kernel - Re: [patch 0/5] Support for sanitization flag in low-level page allocator

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Date:	Thu, 28 May 2009 00:34:21 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Rik van Riel <riel@...hat.com>
Cc:	"Larry H." <research@...reption.com>, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...l.org>, linux-mm@...ck.org,
	Ingo Molnar <mingo@...hat.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, pageexec@...email.hu
Subject: Re: [patch 0/5] Support for sanitization flag in low-level page
	allocator


* Rik van Riel <riel@...hat.com> wrote:

> Ingo Molnar wrote:
>
>> What you are missing is that your patch makes _no technical 
>> sense_ if you allow the same information to leak over the kernel 
>> stack. Kernel stacks can be freed and reused, swapped out and 
>> thus 'exposed'.
>
> Kernel stacks may be freed and reused, but Larry's latest patch 
> takes care of that by clearing them at page free time.
>
> As for being swapped out - I do not believe that kernel stacks can 
> ever be swapped out in Linux.

yes, i referred to that as an undesirable option - because it slows 
down pthread_create() quite substantially.

This needs before/after pthread_create() benchmark results.

	Ingo
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