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Date: Fri, 08 Jul 2016 15:34:19 +1000
From: Michael Ellerman <mpe@...erman.id.au>
To: Kees Cook <keescook@...omium.org>, Arnd Bergmann <arnd@...db.de>
Cc: Jan Kara <jack@...e.cz>, "kernel-hardening\@lists.openwall.com" <kernel-hardening@...ts.openwall.com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, Linux-MM <linux-mm@...ck.org>, sparclinux <sparclinux@...r.kernel.org>, linux-ia64@...r.kernel.org, Christoph Lameter <cl@...ux.com>, Andrea Arcangeli <aarcange@...hat.com>, "x86\@kernel.org" <x86@...nel.org>, Russell King <linux@...linux.org.uk>, Dmitry Vyukov <dvyukov@...gle.com>, David Rientjes <rientjes@...gle.com>, PaX Team <pageexec@...email.hu>, Mathias Krause <minipli@...glemail.com>, linux-arch <linux-arch@...r.kernel.org>, Rik van Riel <riel@...hat.com>, Brad Spengler <spender@...ecurity.net>, Andy Lutomirski <luto@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, "linux-arm-kernel\@lists.infradead.org" <linux-arm-kernel@...ts.infradead.org>, Laura Abbott <labbott@...oraproject.org>, Tony Luck <tony.luck@...el.com>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, LKML <linux-kernel@...r.ker
nel.org>, Fenghua Yu <fenghua.yu@...el.com>, Pekka Enberg <penberg@...nel.org>, Casey Schaufler <casey@...aufler-ca.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, "linuxppc-dev\@lists.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 1/9] mm: Hardened usercopy
Kees Cook <keescook@...omium.org> writes:
> On Thu, Jul 7, 2016 at 4:01 AM, Arnd Bergmann <arnd@...db.de> wrote:
>> On Wednesday, July 6, 2016 3:25:20 PM CEST Kees Cook wrote:
>>> +
>>> + /* Allow kernel rodata region (if not marked as Reserved). */
>>> + if (ptr >= (const void *)__start_rodata &&
>>> + end <= (const void *)__end_rodata)
>>> + return NULL;
>>
>> Should we explicitly forbid writing to rodata, or is it enough to
>> rely on page protection here?
>
> Hm, interesting. That's a very small check to add. My knee-jerk is to
> just leave it up to page protection. I'm on the fence. :)
There are platforms that don't have page protection, so it would be nice
if they could at least opt-in to checking for it here.
cheers
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