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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 2017-08-07 16:20 +0200
Message-ID <ubR2X-W5-51@gated-at.bofh.it> (permalink)
References <ubupJ-3f0-29@gated-at.bofh.it> <ubQgx-ju-1@gated-at.bofh.it> <ubQzU-s0-19@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On 08/07/2017 03:46 PM, Michal Hocko wrote:
> How do they know that they need to regenerate if they do not get SEGV?
> Are they going to assume that a read of zeros is a "must init again"? Isn't
> that too fragile?

Why would it be fragile?  Some level of synchronization is needed to set
things up, of course, but I think it's possible to write a lock-free
algorithm to maintain the state even without strong guarantees of memory
ordering from fork.

In the DRBG uniqueness case, you don't care if you reinitialize because
it's the first use, or because a fork just happened.

In the API-mandated fork check, a detection false positive before a fork
is not acceptable (because it would prevent legitimate API use), but I
think you can deal with this case if you publish a pointer to a
pre-initialized, non-zero mapping.

Thanks,
Florian

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Thread

[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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