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

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On Thu 10-08-17 15:23:05, Colm MacCárthaigh wrote:
> On Thu, Aug 10, 2017 at 3:05 PM, Michal Hocko <mhocko@kernel.org> wrote:
> >> Too late for that. VM_DONTFORK is already implemented
> >> through MADV_DONTFORK & MADV_DOFORK, in a way that is
> >> very similar to the MADV_WIPEONFORK from these patches.
> >
> > Yeah, those two seem to be breaking the "madvise as an advise" semantic as
> > well but that doesn't mean we should follow that pattern any further.
> 
> I would imagine that many of the crypto applications using
> MADV_WIPEONFORK will also be using MADV_DONTDUMP. In cases where it's
> for protecting secret keys, I'd like to use both in my code, for
> example. Though that doesn't really help decide this.
> 
> There is also at least one case for being able to turn WIPEONFORK
> on/off with an existing page; a process that uses privilege separation
> often goes through the following flow:
> 
> 1. [ Access privileged keys as a power user and initialize memory ]
> 2. [ Fork a child process that actually does the work ]
> 3. [ Child drops privileges and uses the memory to do work ]
> 4. [ Parent hangs around to re-spawn a child if it crashes ]
> 
> In that mode it would be convenient to be able to mark the memory as
> WIPEONFORK in the child, but not the parent.

I am not sure I understand. The child will have an own VMA so chaging
the attribute will not affect parent. Or did I misunderstand your
example?

-- 
Michal Hocko
SUSE Labs

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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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