On Mon, 13 Nov 2017, Kirill A. Shutemov wrote: > On Mon, Nov 13, 2017 at 04:43:26PM +0100, Thomas Gleixner wrote: > > 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? > > It will succeed with 5-level paging. And why is this allowed? > It should be safe as with 4-level paging such request would fail and it's > reasonable to expect that userspace is not relying on the failure to > function properly. Huch? The first rule when looking at user space is that is broken or hostile. Reasonable and user space are mutually exclusive. Thanks, tglx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
