Re: [RFC PATCH] Randomization of address chosen by mmap.

[Matthew Wilcox]

On Wed, Feb 28, 2018 at 08:13:00PM +0300, Ilya Smith wrote:
> > It would be worth spelling out the "not recommended" bit some more
> > too: this fragments the mmap space, which has some serious issues on
> > smaller address spaces if you get into a situation where you cannot
> > allocate a hole large enough between the other allocations.
> > 
> 
> Iâm agree, that's the point.

Would it be worth randomising the address returned just ever so slightly?
ie instead of allocating exactly the next address, put in a guard hole
of (configurable, by default maybe) 1-15 pages?  Is that enough extra
entropy to foil an interesting number of attacks, or do we need the full
randomise-the-address-space approach in order to be useful?