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Re: [PATCH 3/3] random: add interrupt callback to VMBus IRQ handler

From Stephan Mueller <smueller@chronox.de>
Newsgroups linux.kernel
Subject Re: [PATCH 3/3] random: add interrupt callback to VMBus IRQ handler
Date 2016-05-02 11:20 +0200
Message-ID <ruibf-JT-1@gated-at.bofh.it> (permalink)
References <rufwK-6Ok-3@gated-at.bofh.it> <rufwL-6Ok-19@gated-at.bofh.it> <rui1A-FW-3@gated-at.bofh.it>
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Am Montag, 2. Mai 2016, 05:00:47 schrieb Jeffrey Walton:

Hi Jeffrey,

> On Mon, May 2, 2016 at 2:26 AM, Theodore Ts'o <tytso@mit.edu> wrote:
> > From: Stephan Mueller <smueller@chronox.de>
> > 
> > The Hyper-V Linux Integration Services use the VMBus implementation for
> > communication with the Hypervisor. VMBus registers its own interrupt
> > handler that completely bypasses the common Linux interrupt handling.
> > This implies that the interrupt entropy collector is not triggered.
> > ...
> 
> Stephan correctly identified the problem of virtualized environments
> in his paper, but there does not appear to be any real defenses in
> place for VM rollback attacks.

The issue the patch addresses is only that on Hyper-V with para-virt drivers, 
the /dev/random implementation does not receive interrupts.

The issue of rollback (if you refer to activating an earlier saved image of 
the guest) is a real issue the guest cannot do anything about it that is 
effective (i.e. the guest can do without the help of the VMM). Note, rollback 
is just a special case of a much broader issue of the duplication of the RNG 
state by the VMM (be it snapshots, move of a guest to another VMM, 
suspend/resume, ...). However, the patch to enable interrupts does not seem to 
be related to that issue as interrupts are not re-issued in case of rollbacks, 
are they?

Ciao
Stephan

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Thread

[RFC PATCH 0/3] random: replace urandom pool with a CRNG Theodore Ts'o <tytso@mit.edu> - 2016-05-02 08:30 +0200
  [PATCH 1/3] random: replace non-blocking pool with a Chacha20-based CRNG Theodore Ts'o <tytso@mit.edu> - 2016-05-02 08:30 +0200
    Re: [PATCH 1/3] random: replace non-blocking pool with a Chacha20-based CRNG Stephan Mueller <smueller@chronox.de> - 2016-05-03 11:00 +0200
      Re: [PATCH 1/3] random: replace non-blocking pool with a  Chacha20-based CRNG Jeffrey Walton <noloader@gmail.com> - 2016-05-04 19:00 +0200
      Re: [PATCH 1/3] random: replace non-blocking pool with a  Chacha20-based CRNG tytso@mit.edu - 2016-05-04 19:40 +0200
        Re: [PATCH 1/3] random: replace non-blocking pool with a Chacha20-based CRNG "H. Peter Anvin" <hpa@zytor.com> - 2016-05-04 20:00 +0200
    Re: [PATCH 1/3] random: replace non-blocking pool with a Chacha20-based CRNG Stephan Mueller <smueller@chronox.de> - 2016-05-03 11:40 +0200
      Re: [PATCH 1/3] random: replace non-blocking pool with a Chacha20-based CRNG Stephan Mueller <smueller@chronox.de> - 2016-05-04 08:30 +0200
    Re: [PATCH 1/3] random: replace non-blocking pool with a  Chacha20-based CRNG Jeffrey Walton <noloader@gmail.com> - 2016-05-04 16:50 +0200
      Re: [PATCH 1/3] random: replace non-blocking pool with a  Chacha20-based CRNG tytso@mit.edu - 2016-05-04 19:50 +0200
        Re: [PATCH 1/3] random: replace non-blocking pool with a  Chacha20-based CRNG Jeffrey Walton <noloader@gmail.com> - 2016-05-04 20:30 +0200
          Re: [PATCH 1/3] random: replace non-blocking pool with a Chacha20-based CRNG "H. Peter Anvin" <hpa@zytor.com> - 2016-05-04 20:40 +0200
            Re: [PATCH 1/3] random: replace non-blocking pool with a  Chacha20-based CRNG tytso@thunk.org - 2016-05-04 21:10 +0200
              Re: [PATCH 1/3] random: replace non-blocking pool with a  Chacha20-based CRNG "H. Peter Anvin" <hpa@zytor.com> - 2016-05-04 23:00 +0200
              Re: [PATCH 1/3] random: replace non-blocking pool with a  Chacha20-based CRNG John Denker <jsd@av8n.com> - 2016-05-04 23:50 +0200
                Re: better patch for linux/bitops.h John Denker <jsd@av8n.com> - 2016-05-05 00:00 +0200
                Re: better patch for linux/bitops.h Jeffrey Walton <noloader@gmail.com> - 2016-05-05 03:40 +0200
                Re: better patch for linux/bitops.h "H. Peter Anvin" <hpa@zytor.com> - 2016-05-05 04:50 +0200
                Re: better patch for linux/bitops.h Jeffrey Walton <noloader@gmail.com> - 2016-05-05 05:00 +0200
                Re: better patch for linux/bitops.h "H. Peter Anvin" <hpa@zytor.com> - 2016-05-05 05:10 +0200
                Re: better patch for linux/bitops.h Jeffrey Walton <noloader@gmail.com> - 2016-05-05 05:40 +0200
                Re: better patch for linux/bitops.h Theodore Ts'o <tytso@mit.edu> - 2016-05-05 06:00 +0200
                Re: better patch for linux/bitops.h Jeffrey Walton <noloader@gmail.com> - 2016-05-05 06:10 +0200
                Re: better patch for linux/bitops.h "H. Peter Anvin" <hpa@zytor.com> - 2016-05-05 08:40 +0200
                Re: UB in general ... and linux/bitops.h in particular John Denker <jsd@av8n.com> - 2016-05-05 18:20 +0200
                Re: UB in general ... and linux/bitops.h in particular Andi Kleen <andi@firstfloor.org> - 2016-05-05 19:40 +0200
                Re: UB in general ... and linux/bitops.h in particular Jeffrey Walton <noloader@gmail.com> - 2016-05-06 04:30 +0200
                Re: better patch for linux/bitops.h Sandy Harris <sandyinchina@gmail.com> - 2016-05-05 23:40 +0200
                Re: better patch for linux/bitops.h tytso@mit.edu - 2016-05-06 00:20 +0200
                Re: better patch for linux/bitops.h "H. Peter Anvin" <hpa@zytor.com> - 2016-05-06 00:30 +0200
                Re: better patch for linux/bitops.h "H. Peter Anvin" <hpa@zytor.com> - 2016-05-06 00:40 +0200
                Re: better patch for linux/bitops.h "H. Peter Anvin" <hpa@zytor.com> - 2016-05-06 02:20 +0200
                Re: [PATCH 1/3] random: replace non-blocking pool with a Chacha20-based CRNG "H. Peter Anvin" <hpa@zytor.com> - 2016-05-05 00:00 +0200
                Re: linux/bitops.h John Denker <jsd@av8n.com> - 2016-05-05 00:10 +0200
                Re: linux/bitops.h Andi Kleen <andi@firstfloor.org> - 2016-05-05 01:10 +0200
                Re: linux/bitops.h John Denker <jsd@av8n.com> - 2016-05-05 02:20 +0200
                Re: linux/bitops.h "H. Peter Anvin" <hpa@zytor.com> - 2016-05-05 03:30 +0200
                Re: linux/bitops.h Jeffrey Walton <noloader@gmail.com> - 2016-05-05 03:30 +0200
                Re: linux/bitops.h "H. Peter Anvin" <hpa@zytor.com> - 2016-05-05 02:40 +0200
                Re: linux/bitops.h Linus Torvalds <torvalds@linux-foundation.org> - 2016-05-05 02:50 +0200
                Re: linux/bitops.h Sasha Levin <sasha.levin@oracle.com> - 2016-05-06 22:10 +0200
                Re: linux/bitops.h Sasha Levin <sasha.levin@oracle.com> - 2016-05-06 22:10 +0200
                Re: linux/bitops.h "H. Peter Anvin" <hpa@zytor.com> - 2016-05-06 22:30 +0200
                Re: linux/bitops.h "H. Peter Anvin" <hpa@zytor.com> - 2016-05-06 22:40 +0200
  [PATCH 2/3] random: make /dev/urandom scalable for silly userspace programs Theodore Ts'o <tytso@mit.edu> - 2016-05-02 08:30 +0200
    Re: [PATCH 2/3] random: make /dev/urandom scalable for silly userspace programs Stephan Mueller <smueller@chronox.de> - 2016-05-02 09:10 +0200
      Re: [PATCH 2/3] random: make /dev/urandom scalable for silly  userspace programs Theodore Ts'o <tytso@mit.edu> - 2016-05-02 15:00 +0200
        Re: [PATCH 2/3] random: make /dev/urandom scalable for silly  userspace programs Theodore Ts'o <tytso@mit.edu> - 2016-05-02 15:50 +0200
          Re: [PATCH 2/3] random: make /dev/urandom scalable for silly userspace programs Stephan Mueller <smueller@chronox.de> - 2016-05-02 16:00 +0200
  [PATCH 3/3] random: add interrupt callback to VMBus IRQ handler Theodore Ts'o <tytso@mit.edu> - 2016-05-02 08:30 +0200
    Re: [PATCH 3/3] random: add interrupt callback to VMBus IRQ handler Jeffrey Walton <noloader@gmail.com> - 2016-05-02 11:10 +0200
      Re: [PATCH 3/3] random: add interrupt callback to VMBus IRQ handler Stephan Mueller <smueller@chronox.de> - 2016-05-02 11:20 +0200
        Re: [PATCH 3/3] random: add interrupt callback to VMBus IRQ handler Theodore Ts'o <tytso@mit.edu> - 2016-05-02 15:00 +0200

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