Re: [RFC, PATCHv2 29/29] mm, x86: introduce RLIMIT_VADDR

[Linus Torvalds]

On Wed, Jan 11, 2017 at 11:20 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>
> Taking a step back, I think it would be fantastic if we could find a
> way to make this work without any inheritable settings at all.
> Perhaps we could have a per-mm value that is initialized to 2^47-1 on
> execve() and can be raised by ELF note or by prctl()?

I definitely think this is the right model. No inheritable settings,
no suid issues, no worries. Make people who want the large address
space (and there aren't going to be a lot of them) just mark their
binaries at compile time.

And as to the stack location: I think it should just be the same
regardless - up in "high" virtual memory in the 47-bit model. Because
as you say, if you actually end up having 57 bits of address space,
that still gives you basically the whole VM for data mappings -
they'll just be up above the stack.

                Linus