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

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Message-ID: <20170811142457.GP30811@dhcp22.suse.cz>
Date:   Fri, 11 Aug 2017 16:24:57 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Florian Weimer <fweimer@...hat.com>
Cc:     Colm MacCárthaigh <colm@...costs.net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Rik van Riel <riel@...hat.com>,
        Will Drewry <wad@...omium.org>, akpm@...ux-foundation.org,
        dave.hansen@...el.com, kirill@...temov.name,
        linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, luto@...capital.net, mingo@...nel.org
Subject: Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK

On Fri 11-08-17 16:11:44, Florian Weimer wrote:
> On 08/11/2017 04:06 PM, Michal Hocko wrote:
> 
> > I am sorry to look too insisting here (I have still hard time to reconcile
> > myself with the madvise (ab)use) but if we in fact want minherit like
> > interface why don't we simply add minherit and make the code which wants
> > to use that interface easier to port? Is the only reason that hooking
> > into madvise is less code? If yes is that a sufficient reason to justify
> > the (ab)use of madvise? If there is a general consensus on that part I
> > will shut up and won't object anymore. Arguably MADV_DONTFORK would fit
> > into minherit API better as well.
> 
> It does, OpenBSD calls it MAP_INHERIT_NONE.
> 
> Could you implement MAP_INHERIT_COPY and MAP_INHERIT_SHARE as well?  Or
> is changing from MAP_SHARED to MAP_PRIVATE and back impossible?

I haven't explored those two very much. Their semantic seems rather
awkward, especially map_inherit_share one. I guess MAP_INHERIT_COPY
would be doable. Do we have to support all modes or a missing support
would disqualify the syscall completely?
-- 
Michal Hocko
SUSE Labs