linux-kernel - Re: [kernel-hardening] [PATCH 4/6] Protectable Memory

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Date:   Mon, 12 Feb 2018 16:40:40 -0800
From:   Laura Abbott <labbott@...hat.com>
To:     Kees Cook <keescook@...omium.org>,
        Igor Stoppa <igor.stoppa@...wei.com>
Cc:     Boris Lukashev <blukashev@...pervictus.com>,
        Christopher Lameter <cl@...ux.com>,
        Matthew Wilcox <willy@...radead.org>,
        Jann Horn <jannh@...gle.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [kernel-hardening] [PATCH 4/6] Protectable Memory

On 02/12/2018 03:27 PM, Kees Cook wrote:
> On Sun, Feb 4, 2018 at 7:05 AM, Igor Stoppa <igor.stoppa@...wei.com> wrote:
>> On 04/02/18 00:29, Boris Lukashev wrote:
>>> On Sat, Feb 3, 2018 at 3:32 PM, Igor Stoppa <igor.stoppa@...wei.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.

Skipping over physmap leaves a pretty big area of exposure that could
be difficult to solve later. I appreciate this might block basic
functionality but I don't think we should just gloss over it without
at least some idea of what we would do.

Thanks,
Laura