linux-kernel - Re: [PATCH] hardening: add PROT_FINAL prot flag to mmap/mprotect

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Date:	Tue, 2 Oct 2012 13:34:06 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Ard Biesheuvel <ard.biesheuvel@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hardening: add PROT_FINAL prot flag to mmap/mprotect

Hi,

On Mon, Aug 20, 2012 at 2:48 PM, Ard Biesheuvel
<ard.biesheuvel@...il.com> wrote:
>> This seems like a good idea to me. It would allow more than just the
>> loader to harden userspace allocations. It's a more direct version of
>> PaX's "MPROTECT" feature[1]. That feature hardens existing loaders,
>> but doesn't play nice with JITs (like Java), but this lets a loader
>> (or JIT) opt-in to the protection and have some direct control over it.
>
> If desired, additional restrictions can be imposed by using the
> security framework, e.g,, disallow non-final r-x mappings.

Interesting; what kind of interface did you have in mind?

>> It seems like there needs to be a sensible way to detect that this flag is
>> available, though.
>
> I am open for suggestions to address this. Our particular
> implementation of the loader (on an embedded system) tries to set it
> on the first mmap invocation, and stops trying if it fails. Not the
> most elegant approach, I know ...

Actually, that seems easiest.

Has there been any more progress on this patch over-all?

-Kees

-- 
Kees Cook
Chrome OS Security
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