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Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK

From Florian Weimer <fweimer@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK
Date 2017-08-11 17:30 +0200
Message-ID <udk2R-5cA-1@gated-at.bofh.it> (permalink)
References (6 earlier) <ucZ86-5c-15@gated-at.bofh.it> <ud3Y5-3tF-5@gated-at.bofh.it> <udiNr-4xf-9@gated-at.bofh.it> <udiX7-4AP-17@gated-at.bofh.it> <udj6P-4Eb-51@gated-at.bofh.it>
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On 08/11/2017 04:24 PM, Michal Hocko wrote:
> 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?

I think it would be a bit awkward if we implemented MAP_INHERIT_ZERO and
it would not turn a shared mapping into a private mapping in the child,
or would not work on shared mappings at all, or deviate in any way from
the OpenBSD implementation.

MAP_INHERIT_SHARE for a MAP_PRIVATE mapping which has been modified is a
bit bizarre, and I don't know how OpenBSD implements any of this.  It
could well be that the exact behavior implemented in OpenBSD is a poor
fit for the Linux VM implementation.

Florian

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[PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK riel@redhat.com - 2017-08-06 16:10 +0200
  Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Michal Hocko <mhocko@kernel.org> - 2017-08-07 15:30 +0200
    Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Michal Hocko <mhocko@kernel.org> - 2017-08-07 15:50 +0200
      Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Florian Weimer <fweimer@redhat.com> - 2017-08-07 16:20 +0200
        Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Michal Hocko <mhocko@kernel.org> - 2017-08-10 15:10 +0200
      Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Rik van Riel <riel@redhat.com> - 2017-08-07 17:10 +0200
        Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-08-09 12:10 +0200
          Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Rik van Riel <riel@redhat.com> - 2017-08-09 14:40 +0200
          Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Florian Weimer <fweimer@redhat.com> - 2017-08-09 14:50 +0200
        Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Michal Hocko <mhocko@kernel.org> - 2017-08-10 15:10 +0200
          Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Colm MacCárthaigh <colm@allcosts.net> - 2017-08-10 15:30 +0200
            Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Michal Hocko <mhocko@kernel.org> - 2017-08-10 17:40 +0200
              Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Michal Hocko <mhocko@kernel.org> - 2017-08-10 19:10 +0200
                Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Colm MacCárthaigh <colm@allcosts.net> - 2017-08-11 00:20 +0200
                Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Michal Hocko <mhocko@kernel.org> - 2017-08-11 16:10 +0200
                Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Florian Weimer <fweimer@redhat.com> - 2017-08-11 16:20 +0200
                Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Michal Hocko <mhocko@kernel.org> - 2017-08-11 16:30 +0200
                Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Florian Weimer <fweimer@redhat.com> - 2017-08-11 17:30 +0200
                Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Michal Hocko <mhocko@kernel.org> - 2017-08-11 17:40 +0200
      Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Colm MacCárthaigh <colm@allcosts.net> - 2017-08-07 18:10 +0200
      Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Michal Hocko <mhocko@kernel.org> - 2017-08-10 15:30 +0200
        Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Michal Hocko <mhocko@kernel.org> - 2017-08-10 16:20 +0200
  Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Mike Kravetz <mike.kravetz@oracle.com> - 2017-08-07 20:30 +0200
    Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Florian Weimer <fweimer@redhat.com> - 2017-08-08 12:00 +0200
      Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Rik van Riel <riel@redhat.com> - 2017-08-08 15:20 +0200
        Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Mike Kravetz <mike.kravetz@oracle.com> - 2017-08-08 17:30 +0200
          Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Florian Weimer <fweimer@redhat.com> - 2017-08-08 17:30 +0200
          Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Rik van Riel <riel@redhat.com> - 2017-08-08 17:50 +0200
            Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Colm MacCárthaigh <colm@allcosts.net> - 2017-08-08 18:50 +0200
            Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Matthew Wilcox <willy@infradead.org> - 2017-08-08 19:00 +0200
              Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Rik van Riel <riel@redhat.com> - 2017-08-08 20:50 +0200
                Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK Michal Hocko <mhocko@kernel.org> - 2017-08-10 17:40 +0200

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