Re: [kernel-hardening] self introduction

[Jann Horn <jann@thejh.net>]

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On Sun, Oct 09, 2016 at 09:09:42PM +0200, Colin Vidal wrote:
> Hi David,
> 
> > If you're interested, the HARDENED_ATOMIC team is looking for people
> > to help porting the feature to other architectures.  ARM is a
> > reasonable candidate for someone new to the project.  I have begun
> > this effort myself, but if you'd like to collaborate I'd be
> > grateful.
> 
> Sounds good!
> 
> > It essentially involves porting the original arch-specific features
> > from PAX_REFCOUNT into Elena Reshetova's official HARDENED_ATOMIC
> > tree, which can be found at
> > https://github.com/esreshetova/linux-stable
> 
> The link seems broken (https://github.com/esreshetova too). I found
> https://github.com/dwindsor/hardened-atomic but it is empty. Did I
> miss something/Github filter?

Typo in the link, I think?
https://github.com/ereshetova/linux-stable


> > Please contact me if you have any questions; I'd be glad to help!
> 
> I actually have question. :-) As far as I understand, PAX_REFCOUNT [1]
> is mainly a x86-only

No, PAX_REFCOUNT also supports a bunch of other architectures. As far as
I can tell from a quick look: ARM, MIPS, PowerPC and SPARC.

> port from PaX project

It is part of the PaX patch.

> in order to avoid overflow
> on atomic_t variable (and avoid use-after-free exploits)

Yes - overflow (beyond INT_MAX) and underflow (beyond INT_MIN).

. I am a
> little bit confused about the Elena patch-set HARDENED_ATOMIC [2]. It
> is a more mature/recent version of the port, isn't it ?

HARDENED_ATOMIC is a patch based on PAX_REFCOUNT that is developed with
the intent to merge it into the upstream kernel.

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