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SubjectRe: [PATCHv2 1/2] x86/mm: Do not allow non-MAP_FIXED mapping across DEFAULT_MAP_WINDOW border
On Tue, 14 Nov 2017, Kirill A. Shutemov wrote:

> On Tue, Nov 14, 2017 at 05:01:50PM +0100, Thomas Gleixner wrote:
> > @@ -198,11 +199,14 @@ arch_get_unmapped_area_topdown(struct fi
> > /* requesting a specific address */
> > if (addr) {
> > addr = PAGE_ALIGN(addr);
> > + if (!mmap_address_hint_valid(addr, len))
> > + goto get_unmapped_area;
> > +
>
> Here and in hugetlb_get_unmapped_area(), we should align the addr after
> the check, not before. Otherwise the alignment itself can bring us over
> the borderline as we align up.

Hmm, then I wonder whether the next check against vm_start_gap() which
checks against the aligned address is correct:

addr = PAGE_ALIGN(addr);
vma = find_vma(mm, addr);

if (end - len >= addr &&
(!vma || addr + len <= vm_start_gap(vma)))
return addr;

Thanks,

tglx

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