[kernel-hardening] [PATCH v2 1/1] powerpc: mm: support ARCH_MMAP_RND_BITS

Bhupesh Sharma bhsharma at redhat.com
Fri Feb 10 18:45:13 AEDT 2017

Hi Michael,

On Tue, Feb 7, 2017 at 7:57 AM, Michael Ellerman <mpe at ellerman.id.au> wrote:
> Bhupesh Sharma <bhsharma at redhat.com> writes:
>> powerpc: arch_mmap_rnd() uses hard-coded values, (23-PAGE_SHIFT) for
>> 32-bit and (30-PAGE_SHIFT) for 64-bit, to generate the random offset
>> for the mmap base address.
>> This value represents a compromise between increased
>> ASLR effectiveness and avoiding address-space fragmentation.
>> Replace it with a Kconfig option, which is sensibly bounded, so that
>> platform developers may choose where to place this compromise.
>> Keep default values as new minimums.
>> This patch makes sure that now powerpc mmap arch_mmap_rnd() approach
>> is similar to other ARCHs like x86, arm64 and arm.
>> Cc: Alexander Graf <agraf at suse.com>
>> Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
>> Cc: Paul Mackerras <paulus at samba.org>
>> Cc: Michael Ellerman <mpe at ellerman.id.au>
>> Cc: Anatolij Gustschin <agust at denx.de>
>> Cc: Alistair Popple <alistair at popple.id.au>
>> Cc: Matt Porter <mporter at kernel.crashing.org>
>> Cc: Vitaly Bordug <vitb at kernel.crashing.org>
>> Cc: Scott Wood <oss at buserror.net>
>> Cc: Kumar Gala <galak at kernel.crashing.org>
>> Cc: Daniel Cashman <dcashman at android.com>
>> Signed-off-by: Bhupesh Sharma <bhsharma at redhat.com>
>> Reviewed-by: Kees Cook <keescook at chromium.org>
>> ---
>> Changes since v1:
>> v1 can be seen here (https://lists.ozlabs.org/pipermail/linuxppc-dev/2017-February/153594.html)
>>     - No functional change in this patch.
>>     - Added R-B from Kees.
>>     - Dropped PATCH 2/2 from v1 as recommended by Kees Cook.
> Thanks for v2.
> But I replied to your v1 with some comments, did you see them?

I have replied to your comments on the original thread.
Please share your views and if possible share your test results on the
PPC setups you might have at your end.


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