Re: [PATCH] x86/mm: Do not allow non-MAP_FIXED mapping across DEFAULT_MAP_WINDOW border

[Thomas Gleixner]

On Tue, 7 Nov 2017, Kirill A. Shutemov wrote:

> In case of 5-level paging, we don't put any mapping above 47-bit, unless
> userspace explicitly asked for it.
> 
> Userspace can ask for allocation from full address space by specifying
> hint address above 47-bit.
> 
> Nicholas noticed that current implementation violates this interface:
> we can get vma partly in high addresses if we ask for a mapping at very
> end of 47-bit address space.
> 
> Let's make sure that, when consider hint address for non-MAP_FIXED
> mapping, start and end of resulting vma are on the same side of 47-bit
> border.

What happens for mappings with MAP_FIXED which cross the border?

Thanks,

	tglx