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Date: Fri, 3 Feb 2017 16:43:51 -0800
From: Kees Cook <keescook@...omium.org>
To: Bhupesh Sharma <bhsharma@...hat.com>
Cc: "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>, 
	"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Daniel Cashman <dcashman@...gle.com>, 
	Michael Ellerman <mpe@...erman.id.au>, Bhupesh SHARMA <bhupesh.linux@...il.com>, 
	Alexander Graf <agraf@...e.com>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, 
	Paul Mackerras <paulus@...ba.org>, Anatolij Gustschin <agust@...x.de>, 
	Alistair Popple <alistair@...ple.id.au>, Matt Porter <mporter@...nel.crashing.org>, 
	Vitaly Bordug <vitb@...nel.crashing.org>, Scott Wood <oss@...error.net>, 
	Kumar Gala <galak@...nel.crashing.org>, Daniel Cashman <dcashman@...roid.com>
Subject: Re: [PATCH v2 1/1] powerpc: mm: support ARCH_MMAP_RND_BITS

On Thu, Feb 2, 2017 at 9:11 PM, Bhupesh Sharma <bhsharma@...hat.com> wrote:
> powerpc: arch_mmap_rnd() uses hard-coded values, (23-PAGE_SHIFT) for
> 32-bit and (30-PAGE_SHIFT) for 64-bit, to generate the random offset
> for the mmap base address.
>
> This value represents a compromise between increased
> ASLR effectiveness and avoiding address-space fragmentation.
> Replace it with a Kconfig option, which is sensibly bounded, so that
> platform developers may choose where to place this compromise.
> Keep default values as new minimums.
>
> This patch makes sure that now powerpc mmap arch_mmap_rnd() approach
> is similar to other ARCHs like x86, arm64 and arm.
>
> Cc: Alexander Graf <agraf@...e.com>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Anatolij Gustschin <agust@...x.de>
> Cc: Alistair Popple <alistair@...ple.id.au>
> Cc: Matt Porter <mporter@...nel.crashing.org>
> Cc: Vitaly Bordug <vitb@...nel.crashing.org>
> Cc: Scott Wood <oss@...error.net>
> Cc: Kumar Gala <galak@...nel.crashing.org>
> Cc: Daniel Cashman <dcashman@...roid.com>
> Signed-off-by: Bhupesh Sharma <bhsharma@...hat.com>
> Reviewed-by: Kees Cook <keescook at chromium.org>

This " at " should be "@", but otherwise, yay v2! :)

-Kees

-- 
Kees Cook
Pixel Security

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