From patchwork Wed Feb 23 22:04:54 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 12757531 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B2E1BC433F5 for ; Wed, 23 Feb 2022 22:05:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243111AbiBWWFp (ORCPT ); Wed, 23 Feb 2022 17:05:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42032 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234750AbiBWWFo (ORCPT ); Wed, 23 Feb 2022 17:05:44 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2F8114DF53; Wed, 23 Feb 2022 14:05:16 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id F0A64B81EB2; Wed, 23 Feb 2022 22:05:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 42EFEC340E7; Wed, 23 Feb 2022 22:05:11 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="p3Fz+yby" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1645653908; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=5pBvrnim267Drxy2tBvWhv9EQxny44tgDJv9yglZOzw=; b=p3Fz+ybysAbMGdmdB0sXZ+aF5mGEdageCUkh7PocknvKbNnTB5XjnKEJVZu7hQtIXjUCRV +iVQK8XXcFoQulzKc8N8w6u3b5+p0WWAQadYInqvn1YWF84YakUvyrd09f56rG73+9IfzQ qfOkaGtHcrR+Y1Y1rmLdap7kDWjWwR4= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id c269c5a0 (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Wed, 23 Feb 2022 22:05:08 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-hyperv@vger.kernel.org, kvm@vger.kernel.org, linux-crypto@vger.kernel.org, qemu-devel@nongnu.org, linux-kernel@vger.kernel.org Cc: "Jason A. Donenfeld" , adrian@parity.io, dwmw@amazon.co.uk, graf@amazon.com, colmmacc@amazon.com, raduweis@amazon.com, imammedo@redhat.com, ehabkost@redhat.com, ben@skyportsystems.com, mst@redhat.com, kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, linux@dominikbrodowski.net, ardb@kernel.org, jannh@google.com, gregkh@linuxfoundation.org, tytso@mit.edu Subject: [PATCH v2 0/2] VM fork detection for RNG Date: Wed, 23 Feb 2022 23:04:54 +0100 Message-Id: <20220223220456.666193-1-Jason@zx2c4.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org This small series picks up work from Amazon that seems to have stalled out last year around this time: listening for the vmgenid ACPI notification, and using it to "do something." Last year, folks proposed a complicated userspace mmap chardev, which was frought with difficulty and evidently abandoned. This year, instead, I have something much simpler in mind: simply using those ACPI notifications to tell the RNG to reinitialize safely, so we don't repeat random numbers in cloned, forked, or rolled-back VM instances. This series consists of two patches. The first one adds the right hooks into the actual RNG, and the second is a driver for the ACPI notification. I had posted an RFC v1 earlier today, thinking I really needed to request comments, lacking much experience with ACPI drivers. But having spent all day reworking this driver, and then testing and debugging it in a variety of circumstances, I feel fairly confident that it works well, so this is now the real thing. Please review! Here's a little screencast showing it in action: https://data.zx2c4.com/vmgenid-appears-to-work.gif As a side note, this series intentionally does _not_ focus on notification of these events to userspace or to other kernel consumers. Since these VM fork detection events first need to hit the RNG, we can later talk about what sorts of notifications or mmap'd counters the RNG should be making accessible to elsewhere. But that's a different sort of project and ties into a lot of more complicated concerns beyond this more basic patchset. So hopefully we can keep the discussion rather focused here to this ACPI business. Changes v1->v2: - [Ard] Correct value of MODULE_LICENSE(). - [Ard] Use ordinary memory accesses instead of memcpy_fromio. - [Ard] Make module a tristate and set MODULE_DEVICE_TABLE(). - [Ard] Free buffer after using. - Use { } instead of { "", 0 }. - Clean up interface into RNG. - Minimize ACPI driver a bit. In addition to the usual suspects, I'm CCing the original team from Amazon who proposed this last year and the QEMU developers who added it there, as well as the kernel Hyper-V maintainers, since this is technically a Microsoft-proposed thing, though QEMU now implements it. Cc: adrian@parity.io Cc: dwmw@amazon.co.uk Cc: graf@amazon.com Cc: colmmacc@amazon.com Cc: raduweis@amazon.com Cc: imammedo@redhat.com Cc: ehabkost@redhat.com Cc: ben@skyportsystems.com Cc: mst@redhat.com Cc: kys@microsoft.com Cc: haiyangz@microsoft.com Cc: sthemmin@microsoft.com Cc: wei.liu@kernel.org Cc: decui@microsoft.com Cc: linux@dominikbrodowski.net Cc: ardb@kernel.org Cc: jannh@google.com Cc: gregkh@linuxfoundation.org Cc: tytso@mit.edu Jason A. Donenfeld (2): random: add mechanism for VM forks to reinitialize crng virt: vmgenid: introduce driver for reinitializing RNG on VM fork drivers/char/random.c | 53 ++++++++++++++++++ drivers/virt/Kconfig | 9 ++++ drivers/virt/Makefile | 1 + drivers/virt/vmgenid.c | 120 +++++++++++++++++++++++++++++++++++++++++ include/linux/random.h | 1 + 5 files changed, 184 insertions(+) create mode 100644 drivers/virt/vmgenid.c