Re: [patch 3/3] x86, mm: get ASLR work for hugetlb mappings

[Ingo Molnar]

* akpm@xxxxxxxxxxxxxxxxxxxx <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:

> From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> Subject: x86, mm: get ASLR work for hugetlb mappings
> 
> Matthew noticed that hugetlb doesn't participate in ASLR on x86-64.  The
> reason is genereic hugetlb_get_unmapped_area() which is used on x86-64. 
> It doesn't support randomization and use bottom-up unmapped area lookup,
> instead of usual top-down on x86-64.
> 
> x86 has arch-specific hugetlb_get_unmapped_area(), but it's used only on
> x86-32.
> 
> Let's use arch-specific hugetlb_get_unmapped_area() on x86-64 too.  It
> fixes the issue and make hugetlb use top-down unmapped area lookup.

So the title and the changelog has typos (I counted three), which 
makes me wonder how well this was tested.

To show/document the testing effort a before/after /proc/PID/maps 
output showing hugetlb vma addresses would be nice, showing that ASLR 
didn't work before and that it works adequately after the patch.

A word about the range and granularity of randomization in the typical 
case would be nice as well.

Thanks,

	Ingo
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