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 02:42:33 -0500 [thread overview] Message-ID: <20220302024137-mutt-send-email-mst@kernel.org> (raw) In-Reply-To: <CAHmME9qieLUDVoPYZPo=N8NCL1T-RzQ4p7kCFv3PKFUkhWZPsw@mail.gmail.com> On Tue, Mar 01, 2022 at 07:37:06PM +0100, Jason A. Donenfeld wrote: > Hi Michael, > > On Tue, Mar 1, 2022 at 6:17 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > Hmm okay, so it's a performance optimization... some batching then? Do > > you really need to worry about every packet? Every 64 packets not > > enough? Packets are after all queued at NICs etc, and VM fork can > > happen after they leave wireguard ... > > Unfortunately, yes, this is an "every packet" sort of thing -- if the > race is to be avoided in a meaningful way. It's really extra bad: > ChaCha20 and AES-CTR work by xoring a secret stream of bytes with > plaintext to produce a ciphertext. If you use that same secret stream > and xor it with a second plaintext and transmit that too, an attacker > can combine the two different ciphertexts to learn things about the > original plaintext. So what about the point about packets queued then? You don't fish packets out of qdisc queues, do you? > But, anyway, it seems like the race is here to stay given what we have > _currently_ available with the virtual hardware. That's why I'm > focused on trying to get something going that's the least bad with > what we've currently got, which is racy by design. How vitally > important is it to have something that doesn't race in the far future? > I don't know, really. It seems plausible that that ACPI notifier > triggers so early that nothing else really even has a chance, so the > race concern is purely theoretical. But I haven't tried to measure > that so I'm not sure. > > Jason
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 02:42:33 -0500 [thread overview] Message-ID: <20220302024137-mutt-send-email-mst@kernel.org> (raw) In-Reply-To: <CAHmME9qieLUDVoPYZPo=N8NCL1T-RzQ4p7kCFv3PKFUkhWZPsw@mail.gmail.com> On Tue, Mar 01, 2022 at 07:37:06PM +0100, Jason A. Donenfeld wrote: > Hi Michael, > > On Tue, Mar 1, 2022 at 6:17 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > Hmm okay, so it's a performance optimization... some batching then? Do > > you really need to worry about every packet? Every 64 packets not > > enough? Packets are after all queued at NICs etc, and VM fork can > > happen after they leave wireguard ... > > Unfortunately, yes, this is an "every packet" sort of thing -- if the > race is to be avoided in a meaningful way. It's really extra bad: > ChaCha20 and AES-CTR work by xoring a secret stream of bytes with > plaintext to produce a ciphertext. If you use that same secret stream > and xor it with a second plaintext and transmit that too, an attacker > can combine the two different ciphertexts to learn things about the > original plaintext. So what about the point about packets queued then? You don't fish packets out of qdisc queues, do you? > But, anyway, it seems like the race is here to stay given what we have > _currently_ available with the virtual hardware. That's why I'm > focused on trying to get something going that's the least bad with > what we've currently got, which is racy by design. How vitally > important is it to have something that doesn't race in the far future? > I don't know, really. It seems plausible that that ACPI notifier > triggers so early that nothing else really even has a chance, so the > race concern is purely theoretical. But I haven't tried to measure > that so I'm not sure. > > Jason
next prev parent reply other threads:[~2022-03-02 7:42 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 [this message] 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 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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