linux-kernel - Re: [PATCH v3 1/2] random: add mechanism for VM forks to reinitialize crng

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Date:   Fri, 25 Feb 2022 12:44:47 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     linux-hyperv@...r.kernel.org, KVM list <kvm@...r.kernel.org>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        QEMU Developers <qemu-devel@...gnu.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        adrian@...ity.io, "Woodhouse, David" <dwmw@...zon.co.uk>,
        Alexander Graf <graf@...zon.com>,
        Colm MacCarthaigh <colmmacc@...zon.com>,
        "Weiss, Radu" <raduweis@...zon.com>,
        Daniel P. Berrangé <berrange@...hat.com>,
        Laszlo Ersek <lersek@...hat.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Eduardo Habkost <ehabkost@...hat.com>, ben@...portsystems.com,
        "Michael S. Tsirkin" <mst@...hat.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Eric Biggers <ebiggers@...nel.org>,
        Jann Horn <jannh@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Theodore Y. Ts'o" <tytso@....edu>,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH v3 1/2] random: add mechanism for VM forks to reinitialize crng

On Fri, 25 Feb 2022 at 12:44, Jason A. Donenfeld <Jason@...c4.com> wrote:
>
> On Fri, Feb 25, 2022 at 12:26 PM Ard Biesheuvel <ardb@...nel.org> wrote:
> >
> > On Thu, 24 Feb 2022 at 14:39, Jason A. Donenfeld <Jason@...c4.com> wrote:
> > >
> > > When a VM forks, we must immediately mix in additional information to
> > > the stream of random output so that two forks or a rollback don't
> > > produce the same stream of random numbers, which could have catastrophic
> > > cryptographic consequences. This commit adds a simple API, add_vmfork_
> > > randomness(), for that, by force reseeding the crng.
> > >
> > > This has the added benefit of also draining the entropy pool and setting
> > > its timer back, so that any old entropy that was there prior -- which
> > > could have already been used by a different fork, or generally gone
> > > stale -- does not contribute to the accounting of the next 256 bits.
> > >
> > > Cc: Dominik Brodowski <linux@...inikbrodowski.net>
> > > Cc: Theodore Ts'o <tytso@....edu>
> > > Cc: Jann Horn <jannh@...gle.com>
> > > Cc: Eric Biggers <ebiggers@...gle.com>
> > > Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
> >
> > Acked-by: Ard Biesheuvel <ardb@...nel.org>
>
> Okay if I treat this as a Reviewed-by instead?

Sure no problem.

Reviewed-by: Ard Biesheuvel <ardb@...nel.org>