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Re: [RFC v1 00/14] Bus1 Kernel Message Bus

From Linus Torvalds <torvalds@linux-foundation.org>
Newsgroups linux.kernel
Subject Re: [RFC v1 00/14] Bus1 Kernel Message Bus
Date 2016-10-26 21:50 +0200
Message-ID <swCn0-8eE-29@gated-at.bofh.it> (permalink)
References <swC3D-87o-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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So the thing that tends to worry me about these is resource management.

If I understood the documentation correctly, this has per-user
resource management, which guarantees that at least the system won't
run out of memory. Good. The act of sending a message transfers the
resource to the receiver end. Fine.

However, the usual problem ends up being that a bad user can basically
DoS a system agent, especially since for obvious performance reasons
the send/receive has to be asynchronous.

So the usual DoS model is that some user just sends a lot of messages
to a system agent, filling up the system agent resource quota, and
basically killing the system. No, it didn't run out of memory, but the
system agent may not be able to do anything more, since it is now out
of resources.

Keeping the resource management with the sender doesn't solve the
problem, it just reverses it: now the attack will be to send a lot of
queries to the system agent, but then just refuse to listen to the
replies - again causing the system agent to run out of resources.

Usually the way this is resolved this is by forcing a
"request-and-reply" resource management model, where the person who
sends out a request is not only the one who is accounted for the
request, but also accounted for the reply buffer. That way the system
agent never runs out of resources, because it's always the requesting
party that has its resources accounted, never the system agent.

You may well have solved this, but can you describe what the solution
is without forcing people to read the code and try to analyze it?

               Linus

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[RFC v1 00/14] Bus1 Kernel Message Bus David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 21:30 +0200
  [RFC v1 02/14] bus1: provide stub cdev /dev/bus1 David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 21:30 +0200
    Re: [RFC v1 02/14] bus1: provide stub cdev /dev/bus1 Andy Lutomirski <luto@amacapital.net> - 2016-10-27 01:30 +0200
      Re: [RFC v1 02/14] bus1: provide stub cdev /dev/bus1 Tom Gundersen <teg@jklm.no> - 2016-10-27 02:00 +0200
        Re: [RFC v1 02/14] bus1: provide stub cdev /dev/bus1 Arnd Bergmann <arnd@arndb.de> - 2016-10-27 11:20 +0200
          Re: [RFC v1 02/14] bus1: provide stub cdev /dev/bus1 Tom Gundersen <teg@jklm.no> - 2016-10-27 17:30 +0200
            Re: [RFC v1 02/14] bus1: provide stub cdev /dev/bus1 Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-27 18:40 +0200
              Re: [RFC v1 02/14] bus1: provide stub cdev /dev/bus1 Tom Gundersen <teg@jklm.no> - 2016-10-27 18:50 +0200
            Re: [RFC v1 02/14] bus1: provide stub cdev /dev/bus1 Arnd Bergmann <arnd@arndb.de> - 2016-10-30 00:20 +0200
  [RFC v1 09/14] bus1: provide transaction context for multicasts David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 21:30 +0200
    Re: [RFC v1 09/14] bus1: provide transaction context for multicasts Peter Zijlstra <peterz@infradead.org> - 2016-10-28 16:40 +0200
  [RFC v1 07/14] bus1: tracking user contexts David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 21:30 +0200
  [RFC v1 03/14] bus1: util - active reference utility library David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 21:30 +0200
  [RFC v1 05/14] bus1: util - pool utility library David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 21:30 +0200
    Re: [RFC v1 05/14] bus1: util - pool utility library Peter Zijlstra <peterz@infradead.org> - 2016-10-27 16:00 +0200
      Re: [RFC v1 05/14] bus1: util - pool utility library Peter Zijlstra <peterz@infradead.org> - 2016-10-27 17:10 +0200
    Re: [RFC v1 05/14] bus1: util - pool utility library Peter Zijlstra <peterz@infradead.org> - 2016-10-27 16:00 +0200
    Re: [RFC v1 05/14] bus1: util - pool utility library Peter Zijlstra <peterz@infradead.org> - 2016-10-27 17:20 +0200
  [RFC v1 04/14] bus1: util - fixed list utility library David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 21:30 +0200
    Re: [RFC v1 04/14] bus1: util - fixed list utility library Peter Zijlstra <peterz@infradead.org> - 2016-10-27 16:30 +0200
      Re: [RFC v1 04/14] bus1: util - fixed list utility library David Herrmann <dh.herrmann@gmail.com> - 2016-10-27 16:50 +0200
  [RFC v1 13/14] bus1: limit and protect resources David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 21:30 +0200
  [RFC v1 08/14] bus1: implement peer management context David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 21:30 +0200
    Re: [RFC v1 08/14] bus1: implement peer management context Richard Weinberger <richard.weinberger@gmail.com> - 2016-10-28 14:10 +0200
      Re: [RFC v1 08/14] bus1: implement peer management context Tom Gundersen <teg@jklm.no> - 2016-10-28 15:20 +0200
        Re: [RFC v1 08/14] bus1: implement peer management context Richard Weinberger <richard@nod.at> - 2016-10-28 15:30 +0200
    Re: [RFC v1 08/14] bus1: implement peer management context Richard Weinberger <richard.weinberger@gmail.com> - 2016-10-28 15:10 +0200
      Re: [RFC v1 08/14] bus1: implement peer management context Tom Gundersen <teg@jklm.no> - 2016-10-28 15:30 +0200
        Re: [RFC v1 08/14] bus1: implement peer management context Richard Weinberger <richard@nod.at> - 2016-10-28 16:00 +0200
  [RFC v1 14/14] bus1: basic user-space kselftests David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 21:30 +0200
  [RFC v1 12/14] bus1: hook up file-operations David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 21:30 +0200
  [RFC v1 01/14] bus1: add bus1(7) man-page David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 21:30 +0200
    Re: [RFC v1 01/14] bus1: add bus1(7) man-page "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-10-29 22:30 +0200
  [RFC v1 11/14] bus1: implement message transmission David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 21:30 +0200
  [RFC v1 06/14] bus1: util - queue utility library David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 21:30 +0200
    Re: [RFC v1 06/14] bus1: util - queue utility library Peter Zijlstra <peterz@infradead.org> - 2016-10-27 17:30 +0200
    Re: [RFC v1 06/14] bus1: util - queue utility library Peter Zijlstra <peterz@infradead.org> - 2016-10-27 18:50 +0200
      Re: [RFC v1 06/14] bus1: util - queue utility library Tom Gundersen <teg@jklm.no> - 2016-10-28 13:40 +0200
        Re: [RFC v1 06/14] bus1: util - queue utility library Peter Zijlstra <peterz@infradead.org> - 2016-10-28 15:40 +0200
          Re: [RFC v1 06/14] bus1: util - queue utility library Tom Gundersen <teg@jklm.no> - 2016-10-28 15:50 +0200
            Re: [RFC v1 06/14] bus1: util - queue utility library Peter Zijlstra <peterz@infradead.org> - 2016-10-28 16:00 +0200
              Re: [RFC v1 06/14] bus1: util - queue utility library Tom Gundersen <teg@jklm.no> - 2016-10-28 16:40 +0200
                Re: [RFC v1 06/14] bus1: util - queue utility library Peter Zijlstra <peterz@infradead.org> - 2016-10-28 18:50 +0200
  Re: [RFC v1 00/14] Bus1 Kernel Message Bus Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-26 21:50 +0200
    Re: [RFC v1 00/14] Bus1 Kernel Message Bus David Herrmann <dh.herrmann@gmail.com> - 2016-10-26 22:40 +0200
      Re: [RFC v1 00/14] Bus1 Kernel Message Bus "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-10-29 22:30 +0200
        Re: [RFC v1 00/14] Bus1 Kernel Message Bus Josh Triplett <josh@joshtriplett.org> - 2016-10-29 23:10 +0200
        Re: [RFC v1 00/14] Bus1 Kernel Message Bus David Herrmann <dh.herrmann@gmail.com> - 2016-11-02 15:50 +0100
  Re: [RFC v1 04/14] bus1: util - fixed list utility library Arnd Bergmann <arnd@arndb.de> - 2016-10-27 16:00 +0200
    Re: [RFC v1 04/14] bus1: util - fixed list utility library David Herrmann <dh.herrmann@gmail.com> - 2016-10-27 16:00 +0200
  Re: [RFC v1 00/14] Bus1 Kernel Message Bus Michael Kerrisk <mtk.manpages@gmail.com> - 2016-10-27 16:40 +0200
  Re: [RFC v1 00/14] Bus1 Kernel Message Bus Richard Weinberger <richard.weinberger@gmail.com> - 2016-10-28 15:20 +0200
    Re: [RFC v1 00/14] Bus1 Kernel Message Bus Tom Gundersen <teg@jklm.no> - 2016-10-28 15:40 +0200

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