linux-kernel - Re: [PATCH v2 0/3] Introduce the latent

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Message-ID: <CAGXu5jLS_NNFYPXgjaHfiF6Bfg4TbzogadOPkdTcxXG8nm7Y2A@mail.gmail.com>
Date:	Thu, 9 Jun 2016 14:18:08 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Emese Revfy <re.emese@...il.com>
Cc:	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	PaX Team <pageexec@...email.hu>,
	Brad Spengler <spender@...ecurity.net>,
	Michal Marek <mmarek@...e.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	linux-kbuild <linux-kbuild@...r.kernel.org>,
	"Theodore Ts'o" <tytso@....edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>, Jens Axboe <axboe@...nel.dk>,
	Al Viro <viro@...iv.linux.org.uk>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	bart.vanassche@...disk.com, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v2 0/3] Introduce the latent_entropy gcc plugin

On Mon, May 30, 2016 at 4:30 PM, Emese Revfy <re.emese@...il.com> wrote:
> I would like to introduce the latent_entropy gcc plugin. This plugin mitigates
> the problem of the kernel having too little entropy during and after boot
> for generating crypto keys.
>
> This plugin mixes random values into the latent_entropy global variable
> in functions marked by the __latent_entropy attribute.
> The value of this global variable is added to the kernel entropy pool
> to increase the entropy.
>
> It is a CII project supported by the Linux Foundation.
>
> The latent_entropy plugin was ported from grsecurity/PaX originally written by
> the PaX Team. You can find more about the plugin here:
> https://grsecurity.net/pipermail/grsecurity/2012-July/001093.html
>
> The plugin supports all gcc version from 4.5 to 6.0.
>
> I do some changes above the PaX version. The important one is mixing
> the stack pointer into the global variable too.
> You can find more about the changes here:
> https://github.com/ephox-gcc-plugins/latent_entropy
>
> This patch set is based on the "Introduce GCC plugin infrastructure" patch set (v9 next-20160520).
>
> Emese Revfy (3):
>  Add the latent_entropy gcc plugin
>  Mark functions with the latent_entropy attribute
>  Add the extra_latent_entropy kernel parameter
>
>
> Changes from v1:
>   * Remove unnecessary ifdefs
>     (Suggested-by: Kees Cook <keescook@...omium.org>)
>   * Separate the two definitions of add_latent_entropy()
>     (Suggested-by: Kees Cook <keescook@...omium.org>)
>   * Removed unnecessary global variable (latent_entropy_plugin.c)
>   * About the latent_entropy gcc attribute (latent_entropy_plugin.c)
>   * Measure the boot time performance impact of the latent_entropy plugin (arch/Kconfig)

By the way, as you work on v3, can you also be sure to put your
patches through scripts/checkpatch.pl? There are a lot of >80
character lines, and other nits. I'd like to minimize the warnings.

Thanks!

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security