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From:   Kees Cook <keescook@chromium.org>
Date:   Wed, 21 Feb 2018 14:24:42 -0800
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Subject: Re: [PATCH 5/6] Pmalloc: self-test
To:     Igor Stoppa <igor.stoppa@huawei.com>
Cc:     Matthew Wilcox <willy@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Michal Hocko <mhocko@kernel.org>,
        Laura Abbott <labbott@redhat.com>,
        Jerome Glisse <jglisse@redhat.com>,
        Christoph Hellwig <hch@infradead.org>,
        Christoph Lameter <cl@linux.com>,
        linux-security-module <linux-security-module@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>
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On Tue, Feb 20, 2018 at 8:40 AM, Igor Stoppa <igor.stoppa@huawei.com> wrote:
>
> On 13/02/18 01:43, Kees Cook wrote:
>> On Mon, Feb 12, 2018 at 8:53 AM, Igor Stoppa <igor.stoppa@huawei.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