[PATCH] D42897: MSan : Adding mmap W|X flag usage optional detection

[Kamil Rytarowski via Phabricator via llvm-commits]

krytarowski added a comment.

In https://reviews.llvm.org/D42897#997426, @devnexen wrote:

> In https://reviews.llvm.org/D42897#997425, @krytarowski wrote:
>
> > I think this is a wrong layer for detecting W|X mapping.
> >
> > This is for FreeBSD in mind, correct?
>
>
> It has nothing to do with operating systems, it s general topic (e.,g. W|X mapping can possibly lead to JIT ROP's like attacks).


This is hardened by existing kernels.

NetBSD has PaX MPROTECT enabled by default.
OpenBSD has W^X.
grsecurity/Linux has something similar.

As far as I can tell Apple pushes for W^X on evbarm64.

We have enough portability pain in LLVM with sys::Memory that is a wrapper for mmap(2). We want to delete it and replace with a less low-lever interface.

Going this route in MSan will be even worse pain. I recommend to harden your kernel directly as mmap(2) isn't so portable. FreeBSD planned to introduce a new replacement for this interface with an option for at least ASLR.

The mmap_prot_write_exec.cc program will break as is on NetBSD.


Repository:
  rCRT Compiler Runtime

https://reviews.llvm.org/D42897