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

[Kirill A. Shutemov]

Ingo Molnar wrote:
> 
> * 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.

What about this: