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

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Message-ID: <20090528124840.GB1421@ucw.cz>
Date:	Thu, 28 May 2009 14:48:40 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Larry H." <research@...reption.com>
Cc:	linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...l.org>,
	linux-mm@...ck.org, Ingo Molnar <mingo@...hat.com>
Subject: Re: [patch 0/5] Support for sanitization flag in low-level page
	allocator

Hi!

> Index: linux-2.6/mm/Kconfig
> ===================================================================
> --- linux-2.6.orig/mm/Kconfig
> +++ linux-2.6/mm/Kconfig
> @@ -155,6 +155,26 @@ config PAGEFLAGS_EXTENDED
>  	def_bool y
>  	depends on 64BIT || SPARSEMEM_VMEMMAP || !NUMA || !SPARSEMEM
>  
> +config PAGE_SENSITIVE
> +	bool "Support for selective page sanitization"
> +	help
> +	 This option provides support for honoring the sensitive bit
> +	 in the low level page allocator. This bit is used to mark
> +	 pages that will contain sensitive information (such as
> +	 cryptographic secrets and credentials).
> +
> +	 Pages marked with the sensitive bit will be sanitized upon
> +	 release, to prevent information leaks and data remanence that
> +	 could allow Iceman/coldboot attacks to reveal such data.
> +
> +	 If you are unsure, select N. This option might introduce a
> +	 minimal performance impact on those subsystems that make
> +	 use of the flag associated with the sensitive bit.
> +
> +	 If you use the cryptographic API or want to prevent tty
> +	 information leaks locally, you most likely want to enable
> +	 this.

This should not be configurable. Runtime config, defaulting to
'sanitize' may make some sense, but... better just be secure.

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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