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

Kees Cook
2016-07-15T04:29:31Z

On Thu, Jul 14, 2016 at 7:05 PM, Balbir Singh <bsingharora@gmail.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@chromium.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