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Message-ID: <CAGXu5j+ivd0Ys++6hqCjkipx8RFKTAmWf+KbtxEwT3SECD5C6A@mail.gmail.com>
Date: Wed, 21 Feb 2018 14:24:42 -0800
From: Kees Cook <keescook@...omium.org>
To: Igor Stoppa <igor.stoppa@...wei.com>
Cc: Matthew Wilcox <willy@...radead.org>, Randy Dunlap <rdunlap@...radead.org>, 
	Jonathan Corbet <corbet@....net>, Michal Hocko <mhocko@...nel.org>, Laura Abbott <labbott@...hat.com>, 
	Jerome Glisse <jglisse@...hat.com>, Christoph Hellwig <hch@...radead.org>, Christoph Lameter <cl@...ux.com>, 
	linux-security-module <linux-security-module@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>, 
	LKML <linux-kernel@...r.kernel.org>, 
	Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH 5/6] Pmalloc: self-test

On Tue, Feb 20, 2018 at 8:40 AM, Igor Stoppa <igor.stoppa@...wei.com> wrote:
>
> On 13/02/18 01:43, Kees Cook wrote:
>> On Mon, Feb 12, 2018 at 8:53 AM, Igor Stoppa <igor.stoppa@...wei.com> wrote:
>
> [...]
>
>>> +obj-$(CONFIG_PROTECTABLE_MEMORY_SELFTEST) += pmalloc-selftest.o
>>
>> Nit: self-test modules are traditionally named "test_$thing.o"
>> (outside of the tools/ directory).
>
> ok
>
> [...]
>
>> I wonder if lkdtm should grow a test too, to validate the RO-ness of
>> the allocations at the right time in API usage?
>
> sorry for being dense ... are you proposing that I do something to
> lkdtm_rodata.c ? An example would probably help me understand.

It would likely live in lkdtm_perms.c (or maybe lkdtm_heap.c). Namely,
use the pmalloc API and then attempt to write to a read-only variable
in the pmalloc region (to prove that the permission adjustment
actually happened). Likely a good example is
lkdtm_WRITE_RO_AFTER_INIT().

-Kees

-- 
Kees Cook
Pixel Security

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