Re: [PATCH] ASLRv3: randomize_va_space=3 preventing offset2lib attack

[Cyrill Gorcunov <gorcunov@gmail.com>]

On Fri, Dec 19, 2014 at 02:11:37PM -0800, Andy Lutomirski wrote:
...
> >
> > Therefore, I can fix the current implementation (maintaining the
> > randomize_va_space=2) by moving the PIE executable from the mmap base
> > area to another one for x86*, ARM* and MIPS (as s390 and PowerPC do).
> > But we shall agree that this increment in the page table is not a
> > issue. Otherwise, the randomize_va_space=3 shall be considered.
> 
> Wrt the vdso itself, though, there is an extra consideration: CRIU.  I
> *think* that the CRIU vdso proxying scheme will work even if the vdso
> changes sizes and is adjacent to other mappings.  Cyrill and/or Pavel,
> am I right?

At least that was the idea. I've been testing old vdso from rhel5 proxified
to 3.x series where vvar segment is present, worked well.

> I'm not fundamentally opposed to mapping the vdso just like any other
> shared library.  I still think that we should have an extra-strong
> randomization mode in which all the libraries are randomized wrt each
> other, though.  For many applications, the extra page table cost will
> be negligible.