linux-kernel - Re: [PATCH v2 0/2] mm,fork,security: introduce MADV

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Date:   Tue, 8 Aug 2017 18:48:17 +0200
From:   Colm MacCárthaigh <colm@...costs.net>
To:     Rik van Riel <riel@...hat.com>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Florian Weimer <fweimer@...hat.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, Kees Cook <keescook@...omium.org>,
        luto@...capital.net, Will Drewry <wad@...omium.org>,
        mingo@...nel.org, kirill@...temov.name, dave.hansen@...el.com
Subject: Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK

On Tue, Aug 8, 2017 at 5:46 PM, Rik van Riel <riel@...hat.com> wrote:

>> If the use case is fairly specific, then perhaps it makes sense to
>> make MADV_WIPEONFORK not applicable (EINVAL) for mappings where the
>> result is 'questionable'.
>
> That would be a question for Florian and Colm.
>
> If they are OK with MADV_WIPEONFORK only working on
> anonymous VMAs (no file mapping), that certainly could
> be implemented.

Anonymous would be sufficient for all of the Crypto-cases that I've
come across. But I can imagine someone wanting to initialize all
application state from a saved file, or share it between processes.

The comparable minherit call sidesteps all of this by simply
documenting that it results in a new anonymous page after fork, and so
the previous state doesn't matter.

Maybe the problem here is the poor name (my fault). WIPEONFORK
suggests an action being taken ... like a user might think that it
literally zeroes a file, for example.  At the risk of bike shedding:
maybe ZEROESONFORK would resolve that small ambiguity?

-- 
Colm