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

[Michael Ellerman]

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?

cheers