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From:   Kees Cook <keescook@chromium.org>
Date:   Mon, 12 Feb 2018 15:27:19 -0800
Message-ID: <CAGXu5j+LS1pgOOroi7Yxp2nh=DwtTnU3p-NZa6bQu_wkvvVkwg@mail.gmail.com>
Subject: Re: [kernel-hardening] [PATCH 4/6] Protectable Memory
To:     Igor Stoppa <igor.stoppa@huawei.com>
Cc:     Boris Lukashev <blukashev@sempervictus.com>,
        Christopher Lameter <cl@linux.com>,
        Matthew Wilcox <willy@infradead.org>,
        Jann Horn <jannh@google.com>,
        Jerome Glisse <jglisse@redhat.com>,
        Michal Hocko <mhocko@kernel.org>,
        Laura Abbott <labbott@redhat.com>,
        Christoph Hellwig <hch@infradead.org>,
        linux-security-module <linux-security-module@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        kernel list <linux-kernel@vger.kernel.org>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>
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On Sun, Feb 4, 2018 at 7:05 AM, Igor Stoppa <igor.stoppa@huawei.com> wrote:
> On 04/02/18 00:29, Boris Lukashev wrote:
>> On Sat, Feb 3, 2018 at 3:32 PM, Igor Stoppa <igor.stoppa@huawei.com> wrote:
>
> [...]
>
>>> What you are suggesting, if I have understood it correctly, is that,
>>> when the pool is protected, the addresses already given out, will become
>>> traps that get resolved through a lookup table that is built based on
>>> the content of each allocation.
>>>
>>> That seems to generate a lot of overhead, not to mention the fact that
>>> it might not play very well with the MMU.
>>
>> That is effectively what i'm suggesting - as a form of protection for
>> consumers against direct reads of data which may have been corrupted
>> by some irrelevant means. In the context of pmalloc, it would probably
>> be a separate type of ro+verified pool
> ok, that seems more like an extension though.
>
> ATM I am having problems gaining traction to get even the basic merged :-)
>
> I would consider this as a possibility for future work, unless it is
> said that it's necessary for pmalloc to be accepted ...

I would agree: let's get basic functionality in first. Both
verification and the physmap part can be done separately, IMO.

-Kees

-- 
Kees Cook
Pixel Security