Received: by 2002:a05:6a10:8c0a:0:0:0:0 with SMTP id go10csp264070pxb; Wed, 24 Feb 2021 01:11:51 -0800 (PST) X-Google-Smtp-Source: ABdhPJyd7zrHzwsGO7oIbiQVSgWRwfcy3Uok1OMn0Un9pMp2H+AIAO1uHA/WlkbIRSrM+6wj68tw X-Received: by 2002:a17:906:51cf:: with SMTP id v15mr807599ejk.544.1614157911714; Wed, 24 Feb 2021 01:11:51 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1614157911; cv=none; d=google.com; s=arc-20160816; b=hQpX8vu77fyVWqSUxsHIXIZaEQcBdg3y+7fT7M1YqGrE9tWjHaEVBE8dXIKTfoKRv+ HVH21DlAJya+nBv7ySDcNLzD5wJYiVqKF97nRta0rt1KQD3UaXkaRjyVA1SWNBmnVSP1 Dc/3400VIJgk5CYFgtn2fI98U4pnx2HuF3Bz5GiGtMBZZ7EceGfS9N1aFEfnV8zpJsm8 teF3cYwqlAQ6tXQtbyThCHreVZt1zODfyK32uVXcr1li+Qhw+bXdluwqZLnPCN1nDRw9 hGh9Lp1P5gBgIY0+P852oVcBhlkG8VRwn1GqAbnWM/WfItI6Gv7Hze/LWYXpWF0psL5z kLDg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:in-reply-to:content-transfer-encoding :content-disposition:mime-version:references:message-id:subject:cc :to:from:date:dkim-signature; bh=QqFm1NSygbJXw0rWa68aFsGxKE3C5g6IlhiIzb/mOPY=; b=TdjbXOsKaI8WOoOcTYJqKpi2+KV1zIZq0e5xvkwUpYlFO/WCyAW1+sh/p7SlFKyYQT qrROX7RuNTiHMn7/zFKaihF486inHDbc4DLw24u7SUVsxk+nlHx6ugtOYJFszZjAk48n 6MGbsIcAot9w8Svld1DuD52A+OrNajKwsDMLB0hn1Kz3sGugfXa2pfo+TYOhp5hzOQ0/ Ktf8OkVHVjrQaVJGk8l93FgTf7Iu7XQNL+FwV2mTtlLeo8FVVPrnDS6nQkul7dJpQttV 4U8fu2oO1oHuLYHnTDImJgwsfsSx7JvRj09zEvjHH1paleKN0FFK5xnJf217rYxBr8hl d/xw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b="P9im5AN/"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id zm17si1017662ejb.174.2021.02.24.01.11.28; Wed, 24 Feb 2021 01:11:51 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b="P9im5AN/"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234451AbhBXJJG (ORCPT + 99 others); Wed, 24 Feb 2021 04:09:06 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:31645 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234267AbhBXJGr (ORCPT ); Wed, 24 Feb 2021 04:06:47 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614157516; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QqFm1NSygbJXw0rWa68aFsGxKE3C5g6IlhiIzb/mOPY=; b=P9im5AN/uNSCrpyn3E7l/QvzEUCgB8w+0VQ6794A8pMtbixa0RoK/nVE1bfN9c7RnJj/H3 yFboQ9QXh3ihyIxAvhjv0m9xYU2f+RoNfeCC4yo62GyRGLdoThNWnf0rrhdvDcZQFIj5yN ka8DUTO2h3JynGOJTunEvo7Z2/GrMSw= Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-197-YJAhioV8NvS-MfADh6Xjsg-1; Wed, 24 Feb 2021 04:05:14 -0500 X-MC-Unique: YJAhioV8NvS-MfADh6Xjsg-1 Received: by mail-ed1-f71.google.com with SMTP id l6so542750edn.22 for ; Wed, 24 Feb 2021 01:05:13 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=QqFm1NSygbJXw0rWa68aFsGxKE3C5g6IlhiIzb/mOPY=; b=HdtPj1ATFPnFrMq585WEZeJgaPf8i0/z7K6CYU+fXql+mj2h6BVtteQEbfHO3sxO4x yMe1FcbK5FVYG00syY2owvZhyu38EWOmS2oQ+XA7cRtHnfgqBbqcoslOWA4RWsJC2WPF 6riF/lSa/TXSOieF8wMSgnPmp7XT7oPLbWOFWRCNk0b3zyxZwreCAIDQbHi9xbWw3WS0 mGX6QJ+mFXyPrS4zHOjWobLQ9YY+NfxJ94nH/IDyuOfVBccuer9NaQs2QfBOaMZo8FjP uCd9sqrJo0xuCSJ1NtwOKC2vAR2zLwq6QH0K3LY7JPvYP2ZkoBa4EvtUf5c8YJVMVdhA jGig== X-Gm-Message-State: AOAM530jZ06/nCdRFpEDhAyKzct9LH+x4xMDfj92CgrQASkodNggHrEe loXhk8IT1nRERJ3GZWuhGl2F1XphEKW+6moBBbeOsa+lnAK7FX+bawztqn3anrbWA8iziq3o8+5 Jx5kSji/UgCJCFAYPMLes5ShH X-Received: by 2002:a17:906:27cc:: with SMTP id k12mr30689080ejc.8.1614157512118; Wed, 24 Feb 2021 01:05:12 -0800 (PST) X-Received: by 2002:a17:906:27cc:: with SMTP id k12mr30689054ejc.8.1614157511871; Wed, 24 Feb 2021 01:05:11 -0800 (PST) Received: from redhat.com (bzq-79-180-2-31.red.bezeqint.net. [79.180.2.31]) by smtp.gmail.com with ESMTPSA id t8sm818884ejr.71.2021.02.24.01.05.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Feb 2021 01:05:10 -0800 (PST) Date: Wed, 24 Feb 2021 04:05:05 -0500 From: "Michael S. Tsirkin" To: Adrian Catangiu Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, kvm@vger.kernel.org, linux-s390@vger.kernel.org, gregkh@linuxfoundation.org, graf@amazon.com, rdunlap@infradead.org, arnd@arndb.de, ebiederm@xmission.com, rppt@kernel.org, 0x7f454c46@gmail.com, borntraeger@de.ibm.com, Jason@zx2c4.com, jannh@google.com, w@1wt.eu, colmmacc@amazon.com, luto@kernel.org, tytso@mit.edu, ebiggers@kernel.org, dwmw@amazon.co.uk, bonzini@gnu.org, sblbir@amazon.com, raduweis@amazon.com, corbet@lwn.net, mhocko@kernel.org, rafael@kernel.org, pavel@ucw.cz, mpe@ellerman.id.au, areber@redhat.com, ovzxemul@gmail.com, avagin@gmail.com, ptikhomirov@virtuozzo.com, gil@azul.com, asmehra@redhat.com, dgunigun@redhat.com, vijaysun@ca.ibm.com, oridgar@gmail.com, ghammer@redhat.com Subject: Re: [PATCH v7 0/2] System Generation ID driver and VMGENID backend Message-ID: <20210224040034-mutt-send-email-mst@kernel.org> References: <1614156452-17311-1-git-send-email-acatan@amazon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1614156452-17311-1-git-send-email-acatan@amazon.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 24, 2021 at 10:47:30AM +0200, Adrian Catangiu wrote: > This feature is aimed at virtualized or containerized environments > where VM or container snapshotting duplicates memory state, which is a > challenge for applications that want to generate unique data such as > request IDs, UUIDs, and cryptographic nonces. > > The patch set introduces a mechanism that provides a userspace > interface for applications and libraries to be made aware of uniqueness > breaking events such as VM or container snapshotting, and allow them to > react and adapt to such events. > > Solving the uniqueness problem strongly enough for cryptographic > purposes requires a mechanism which can deterministically reseed > userspace PRNGs with new entropy at restore time. This mechanism must > also support the high-throughput and low-latency use-cases that led > programmers to pick a userspace PRNG in the first place; be usable by > both application code and libraries; allow transparent retrofitting > behind existing popular PRNG interfaces without changing application > code; it must be efficient, especially on snapshot restore; and be > simple enough for wide adoption. > > The first patch in the set implements a device driver which exposes a > the /dev/sysgenid char device to userspace. Its associated filesystem > operations operations can be used to build a system level safe workflow > that guest software can follow to protect itself from negative system > snapshot effects. > > The second patch in the set adds a VmGenId driver which makes use of > the ACPI vmgenid device to drive SysGenId and to reseed kernel entropy > following VM snapshots. > > **Please note**, SysGenID alone does not guarantee complete snapshot > safety to applications using it. A certain workflow needs to be > followed at the system level, in order to make the system > snapshot-resilient. Please see the "Snapshot Safety Prerequisites" > section in the included SysGenID documentation. > > --- > > v6 -> v7: > - remove sysgenid uevent How about we drop mmap too? There's simply no way I can see to make it safe, and no implementation is worse than a racy one imho. Yea there's some decumentation explaining how it is not supposed to be used but it will *seem* to work for people and we will be stuck trying to maintain it. Let's see if userspace using this often enough to make the system call > v5 -> v6: > > - sysgenid: watcher tracking disabled by default > - sysgenid: add SYSGENID_SET_WATCHER_TRACKING ioctl to allow each > file descriptor to set whether they should be tracked as watchers > - rename SYSGENID_FORCE_GEN_UPDATE -> SYSGENID_TRIGGER_GEN_UPDATE > - rework all documentation to clearly capture all prerequisites for > achieving snapshot safety when using the provided mechanism > - sysgenid documentation: replace individual filesystem operations > examples with a higher level example showcasing system-level > snapshot-safe workflow > > v4 -> v5: > > - sysgenid: generation changes are also exported through uevents > - remove SYSGENID_GET_OUTDATED_WATCHERS ioctl > - document sysgenid ioctl major/minor numbers > > v3 -> v4: > > - split functionality in two separate kernel modules: > 1. drivers/misc/sysgenid.c which provides the generic userspace > interface and mechanisms > 2. drivers/virt/vmgenid.c as VMGENID acpi device driver that seeds > kernel entropy and acts as a driving backend for the generic > sysgenid > - rename /dev/vmgenid -> /dev/sysgenid > - rename uapi header file vmgenid.h -> sysgenid.h > - rename ioctls VMGENID_* -> SYSGENID_* > - add ‘min_gen’ parameter to SYSGENID_FORCE_GEN_UPDATE ioctl > - fix races in documentation examples > > v2 -> v3: > > - separate the core driver logic and interface, from the ACPI device. > The ACPI vmgenid device is now one possible backend > - fix issue when timeout=0 in VMGENID_WAIT_WATCHERS > - add locking to avoid races between fs ops handlers and hw irq > driven generation updates > - change VMGENID_WAIT_WATCHERS ioctl so if the current caller is > outdated or a generation change happens while waiting (thus making > current caller outdated), the ioctl returns -EINTR to signal the > user to handle event and retry. Fixes blocking on oneself > - add VMGENID_FORCE_GEN_UPDATE ioctl conditioned by > CAP_CHECKPOINT_RESTORE capability, through which software can force > generation bump > > v1 -> v2: > > - expose to userspace a monotonically increasing u32 Vm Gen Counter > instead of the hw VmGen UUID > - since the hw/hypervisor-provided 128-bit UUID is not public > anymore, add it to the kernel RNG as device randomness > - insert driver page containing Vm Gen Counter in the user vma in > the driver's mmap handler instead of using a fault handler > - turn driver into a misc device driver to auto-create /dev/vmgenid > - change ioctl arg to avoid leaking kernel structs to userspace > - update documentation > > Adrian Catangiu (2): > drivers/misc: sysgenid: add system generation id driver > drivers/virt: vmgenid: add vm generation id driver > > Documentation/misc-devices/sysgenid.rst | 229 +++++++++++++++ > Documentation/userspace-api/ioctl/ioctl-number.rst | 1 + > Documentation/virt/vmgenid.rst | 36 +++ > MAINTAINERS | 15 + > drivers/misc/Kconfig | 15 + > drivers/misc/Makefile | 1 + > drivers/misc/sysgenid.c | 322 +++++++++++++++++++++ > drivers/virt/Kconfig | 13 + > drivers/virt/Makefile | 1 + > drivers/virt/vmgenid.c | 153 ++++++++++ > include/uapi/linux/sysgenid.h | 18 ++ > 11 files changed, 804 insertions(+) > create mode 100644 Documentation/misc-devices/sysgenid.rst > create mode 100644 Documentation/virt/vmgenid.rst > create mode 100644 drivers/misc/sysgenid.c > create mode 100644 drivers/virt/vmgenid.c > create mode 100644 include/uapi/linux/sysgenid.h > > -- > 2.7.4 > > > > > Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. Registered in Romania. Registration number J22/2621/2005.