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Date: Thu, 7 Jul 2016 13:25:21 -0400
From: Kees Cook <keescook@...omium.org>
To: Baruch Siach <baruch@...s.co.il>
Cc: LKML <linux-kernel@...r.kernel.org>, Jan Kara <jack@...e.cz>, 
	"kernel-hardening@...ts.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>, linux-arch <linux-arch@...r.kernel.org>, 
	Michael Ellerman <mpe@...erman.id.au>, "x86@...nel.org" <x86@...nel.org>, 
	Russell King <linux@...linux.org.uk>, 
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, 
	Benjamin Herrenschmidt <benh@...nel.crashing.org>, PaX Team <pageexec@...email.hu>, 
	Borislav Petkov <bp@...e.de>, Mathias Krause <minipli@...glemail.com>, Fenghua Yu <fenghua.yu@...el.com>, 
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	David Rientjes <rientjes@...gle.com>, Tony Luck <tony.luck@...el.com>, 
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	Dmitry Vyukov <dvyukov@...gle.com>, Laura Abbott <labbott@...oraproject.org>, 
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	Andrew Morton <akpm@...ux-foundation.org>, 
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 1/9] mm: Hardened usercopy

On Thu, Jul 7, 2016 at 1:37 AM, Baruch Siach <baruch@...s.co.il> wrote:
> Hi Kees,
>
> On Wed, Jul 06, 2016 at 03:25:20PM -0700, Kees Cook wrote:
>> +#ifdef CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR
>
> Should be CONFIG_HARDENED_USERCOPY to match the slab/slub implementation
> condition.
>
>> +const char *__check_heap_object(const void *ptr, unsigned long n,
>> +                             struct page *page);
>> +#else
>> +static inline const char *__check_heap_object(const void *ptr,
>> +                                           unsigned long n,
>> +                                           struct page *page)
>> +{
>> +     return NULL;
>> +}
>> +#endif

Hmm, I think what I have is correct: if the allocator supports the
heap object checking, it defines __check_heap_object as existing via
CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR. If usercopy checking is done
at all is controlled by CONFIG_HARDENED_USERCOPY.

I.e. you can have the other usercopy checks even if your allocator
doesn't support object size checking.

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security

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