From: "Michael S. Tsirkin" <mst@redhat.com>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: "Laszlo Ersek" <lersek@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
"KVM list" <kvm@vger.kernel.org>,
"QEMU Developers" <qemu-devel@nongnu.org>,
linux-hyperv@vger.kernel.org,
"Linux Crypto Mailing List" <linux-crypto@vger.kernel.org>,
"Alexander Graf" <graf@amazon.com>,
"Michael Kelley (LINUX)" <mikelley@microsoft.com>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
adrian@parity.io, "Daniel P. Berrangé" <berrange@redhat.com>,
"Dominik Brodowski" <linux@dominikbrodowski.net>,
"Jann Horn" <jannh@google.com>,
"Rafael J. Wysocki" <rafael@kernel.org>,
"Brown, Len" <len.brown@intel.com>, "Pavel Machek" <pavel@ucw.cz>,
"Linux PM" <linux-pm@vger.kernel.org>,
"Colm MacCarthaigh" <colmmacc@amazon.com>,
"Theodore Ts'o" <tytso@mit.edu>, "Arnd Bergmann" <arnd@arndb.de>
Subject: Re: propagating vmgenid outward and upward
Date: Wed, 2 Mar 2022 12:27:24 -0500 [thread overview]
Message-ID: <20220302122640-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <Yh+cB5bWarl8CFN1@zx2c4.com>
On Wed, Mar 02, 2022 at 05:32:07PM +0100, Jason A. Donenfeld wrote:
> Hi Michael,
>
> On Wed, Mar 02, 2022 at 11:22:46AM -0500, Michael S. Tsirkin wrote:
> > > Because that 16 byte read of vmgenid is not atomic. Let's say you read
> > > the first 8 bytes, and then the VM is forked.
> >
> > But at this point when VM was forked plaintext key and nonce are all in
> > buffer, and you previously indicated a fork at this point is harmless.
> > You wrote "If it changes _after_ that point of check ... it doesn't
> > matter:"
>
> Ahhh, fair point. I think you're right.
>
> Alright, so all we're talking about here is an ordinary 16-byte read,
> and 16 bytes of storage per keypair, and a 16-byte comparison.
>
> Still seems much worse than just having a single word...
>
> Jason
And it is, I saw a 30% higher overhead, it is however 30% of a very
low number ;)
--
MST
WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: "Brown, Len" <len.brown@intel.com>,
linux-hyperv@vger.kernel.org,
"Colm MacCarthaigh" <colmmacc@amazon.com>,
"Daniel P. Berrangé" <berrange@redhat.com>,
adrian@parity.io, "KVM list" <kvm@vger.kernel.org>,
"Jann Horn" <jannh@google.com>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Linux PM" <linux-pm@vger.kernel.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"Dominik Brodowski" <linux@dominikbrodowski.net>,
"QEMU Developers" <qemu-devel@nongnu.org>,
"Alexander Graf" <graf@amazon.com>,
"Linux Crypto Mailing List" <linux-crypto@vger.kernel.org>,
"Pavel Machek" <pavel@ucw.cz>, "Theodore Ts'o" <tytso@mit.edu>,
"Michael Kelley (LINUX)" <mikelley@microsoft.com>,
"Laszlo Ersek" <lersek@redhat.com>,
"Arnd Bergmann" <arnd@arndb.de>
Subject: Re: propagating vmgenid outward and upward
Date: Wed, 2 Mar 2022 12:27:24 -0500 [thread overview]
Message-ID: <20220302122640-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <Yh+cB5bWarl8CFN1@zx2c4.com>
On Wed, Mar 02, 2022 at 05:32:07PM +0100, Jason A. Donenfeld wrote:
> Hi Michael,
>
> On Wed, Mar 02, 2022 at 11:22:46AM -0500, Michael S. Tsirkin wrote:
> > > Because that 16 byte read of vmgenid is not atomic. Let's say you read
> > > the first 8 bytes, and then the VM is forked.
> >
> > But at this point when VM was forked plaintext key and nonce are all in
> > buffer, and you previously indicated a fork at this point is harmless.
> > You wrote "If it changes _after_ that point of check ... it doesn't
> > matter:"
>
> Ahhh, fair point. I think you're right.
>
> Alright, so all we're talking about here is an ordinary 16-byte read,
> and 16 bytes of storage per keypair, and a 16-byte comparison.
>
> Still seems much worse than just having a single word...
>
> Jason
And it is, I saw a 30% higher overhead, it is however 30% of a very
low number ;)
--
MST
next prev parent reply other threads:[~2022-03-02 17:28 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-01 15:42 propagating vmgenid outward and upward Jason A. Donenfeld
2022-03-01 16:15 ` Laszlo Ersek
2022-03-01 16:28 ` Jason A. Donenfeld
2022-03-01 16:28 ` Jason A. Donenfeld
2022-03-01 17:17 ` Michael S. Tsirkin
2022-03-01 17:17 ` Michael S. Tsirkin
2022-03-01 18:37 ` Jason A. Donenfeld
2022-03-01 18:37 ` Jason A. Donenfeld
2022-03-02 7:42 ` Michael S. Tsirkin
2022-03-02 7:42 ` Michael S. Tsirkin
2022-03-02 7:48 ` Michael S. Tsirkin
2022-03-02 7:48 ` Michael S. Tsirkin
2022-03-02 8:30 ` Michael S. Tsirkin
2022-03-02 8:30 ` Michael S. Tsirkin
2022-03-02 11:26 ` Jason A. Donenfeld
2022-03-02 11:26 ` Jason A. Donenfeld
2022-03-02 12:58 ` Michael S. Tsirkin
2022-03-02 12:58 ` Michael S. Tsirkin
2022-03-02 13:55 ` Jason A. Donenfeld
2022-03-02 13:55 ` Jason A. Donenfeld
2022-03-02 14:46 ` Michael S. Tsirkin
2022-03-02 14:46 ` Michael S. Tsirkin
2022-03-02 15:14 ` Jason A. Donenfeld
2022-03-02 15:14 ` Jason A. Donenfeld
2022-03-02 15:20 ` Michael S. Tsirkin
2022-03-02 15:20 ` Michael S. Tsirkin
2022-03-02 15:36 ` Jason A. Donenfeld
2022-03-02 15:36 ` Jason A. Donenfeld
2022-03-02 16:22 ` Michael S. Tsirkin
2022-03-02 16:22 ` Michael S. Tsirkin
2022-03-02 16:32 ` Jason A. Donenfeld
2022-03-02 16:32 ` Jason A. Donenfeld
2022-03-02 17:27 ` Michael S. Tsirkin [this message]
2022-03-02 17:27 ` Michael S. Tsirkin
2022-03-03 13:07 ` Michael S. Tsirkin
2022-03-03 13:07 ` Michael S. Tsirkin
2022-03-02 16:29 ` Michael S. Tsirkin
2022-03-02 16:29 ` Michael S. Tsirkin
2022-03-01 16:21 ` Michael S. Tsirkin
2022-03-01 16:21 ` Michael S. Tsirkin
2022-03-01 16:35 ` Jason A. Donenfeld
2022-03-01 16:35 ` Jason A. Donenfeld
2022-03-01 18:01 ` Greg KH
2022-03-01 18:01 ` Greg KH
2022-03-01 18:24 ` Jason A. Donenfeld
2022-03-01 18:24 ` Jason A. Donenfeld
2022-03-01 19:41 ` Greg KH
2022-03-01 19:41 ` Greg KH
2022-03-01 23:12 ` Jason A. Donenfeld
2022-03-01 23:12 ` Jason A. Donenfeld
2022-03-02 14:35 ` Jason A. Donenfeld
2022-03-09 10:10 ` Alexander Graf
2022-03-09 22:02 ` Jason A. Donenfeld
2022-03-09 22:02 ` Jason A. Donenfeld
2022-03-10 11:18 ` Alexander Graf
2022-03-20 22:53 ` Michael S. Tsirkin
2022-03-20 22:53 ` Michael S. Tsirkin
2022-04-19 15:12 ` Jason A. Donenfeld
2022-04-19 15:12 ` Jason A. Donenfeld
2022-04-19 16:43 ` Michael S. Tsirkin
2022-04-19 16:43 ` Michael S. Tsirkin
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