linux-kernel - Re: [PATCH v2 11/11] mm: SLUB hardened usercopy support

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Date:	Thu, 14 Jul 2016 21:29:25 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Balbir Singh <bsingharora@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Rik van Riel <riel@...hat.com>,
	Casey Schaufler <casey@...aufler-ca.com>,
	PaX Team <pageexec@...email.hu>,
	Brad Spengler <spender@...ecurity.net>,
	Russell King <linux@...linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	"x86@...nel.org" <x86@...nel.org>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...e.de>,
	Mathias Krause <minipli@...glemail.com>,
	Jan Kara <jack@...e.cz>, Vitaly Wool <vitalywool@...il.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Laura Abbott <labbott@...oraproject.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, linux-ia64@...r.kernel.org,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	sparclinux <sparclinux@...r.kernel.org>,
	linux-arch <linux-arch@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v2 11/11] mm: SLUB hardened usercopy support

On Thu, Jul 14, 2016 at 7:05 PM, Balbir Singh <bsingharora@...il.com> wrote:
> On Wed, Jul 13, 2016 at 02:56:04PM -0700, Kees Cook wrote:
>> Under CONFIG_HARDENED_USERCOPY, this adds object size checking to the
>> SLUB allocator to catch any copies that may span objects. Includes a
>> redzone handling fix from Michael Ellerman.
>>
>> Based on code from PaX and grsecurity.
>>
>> Signed-off-by: Kees Cook <keescook@...omium.org>
>> ---
>>  init/Kconfig |  1 +
>>  mm/slub.c    | 36 ++++++++++++++++++++++++++++++++++++
>>  2 files changed, 37 insertions(+)
>>
>> diff --git a/init/Kconfig b/init/Kconfig
>> index 798c2020ee7c..1c4711819dfd 100644
>> --- a/init/Kconfig
>> +++ b/init/Kconfig
>> @@ -1765,6 +1765,7 @@ config SLAB
>>
>>  config SLUB
>>       bool "SLUB (Unqueued Allocator)"
>> +     select HAVE_HARDENED_USERCOPY_ALLOCATOR
>
> Should this patch come in earlier from a build perspective? I think
> patch 1 introduces and uses __check_heap_object.

__check_heap_object in patch 1 is protected by a check for
CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR.

It seemed better to be to do arch enablement first, and then add the
per-allocator heap object size check since it was a distinct piece.
I'm happy to rearrange things, though, if there's a good reason.

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security