[PATCH] arm64/mm: Remove hack in mmap randomize layout

Will Deacon will.deacon at arm.com
Tue Nov 18 03:41:20 PST 2014

On Mon, Nov 17, 2014 at 11:02:19PM +0000, Yann Droneaud wrote:
> Since commit 8a0a9bd4db63 ('random: make get_random_int() more
> random'), get_random_int() returns a random value for each call,
> so comment and hack introduced in mmap_rnd() as part of commit
> 1d18c47c735e ('arm64: MMU fault handling and page table management')
> are incorrects.
> Commit 1d18c47c735e seems to use the same hack introduced by
> commit a5adc91a4b44 ('powerpc: Ensure random space between stack
> and mmaps'), latter copied in commit 5a0efea09f42 ('sparc64: Sharpen
> address space randomization calculations.').
> But both architectures were cleaned up as part of commit
> fa8cbaaf5a68 ('powerpc+sparc64/mm: Remove hack in mmap randomize
> layout') as hack is no more needed since commit 8a0a9bd4db63.
> So the present patch removes the comment and the hack around
> get_random_int() on AArch64's mmap_rnd().
> Cc: Dan McGee <dpmcgee at gmail.com>
> Cc: David S. Miller <davem at davemloft.net>
> Cc: Anton Blanchard <anton at samba.org>
> Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> Fixes: 1d18c47c735e ('arm64: MMU fault handling and page table management')
> Signed-off-by: Yann Droneaud <ydroneaud at opteya.com>
> ---
>  arch/arm64/mm/mmap.c | 12 ++----------
>  1 file changed, 2 insertions(+), 10 deletions(-)

Thanks, this looks sensible:

  Acked-by: Will Deacon <will.deacon at arm.com>


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