linux-kernel - Re: [PATCH 4/5] mm: split ET

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Message-ID: <1425513380.32154.13.camel@ellerman.id.au>
Date:	Thu, 05 Mar 2015 10:56:20 +1100
From:	Michael Ellerman <mpe@...erman.id.au>
To:	Kees Cook <keescook@...omium.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Russell King <linux@....linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
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	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
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Subject: Re: [PATCH 4/5] mm: split ET_DYN ASLR from mmap ASLR

On Wed, 2015-03-04 at 13:13 -0800, Kees Cook wrote:
> 
> I had a question in the powerpc-specific change that may have gone unnoticed:
> 
> Can mmap ASLR be safely enabled in the legacy mmap case here? Other archs
> use "mm->mmap_base = TASK_UNMAPPED_BASE + random_factor".
> 
> Separate from this series, do you happen to know if this improvement
> can be made, or if the legacy mmap on powerpc can't handle this?

Yeah I saw that. The short answer is I'm not sure.

I assume we have that distinction for some good reason, but whether we still
need it I don't know. I'll dig a bit and see if anyone can remember the details.

cheers


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