From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04A26C4361B for ; Wed, 16 Dec 2020 14:22:58 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6341B233CE for ; Wed, 16 Dec 2020 14:22:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6341B233CE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:56716 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kpXhg-0002M8-7l for qemu-devel@archiver.kernel.org; Wed, 16 Dec 2020 09:22:56 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:46064) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kpXYt-0002cE-6G for qemu-devel@nongnu.org; Wed, 16 Dec 2020 09:13:51 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:47707) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kpXYr-00073L-5r for qemu-devel@nongnu.org; Wed, 16 Dec 2020 09:13:50 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608128028; 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=/XAG/YfDjXK/daG/b2DTAGpgN1OfdDwi06iLxdoBASU=; b=im+Piypt1PlEF5PMyFwBOb0dliYLIjJHWxJwGx5q3APe3+/FBH7B8unigjExyEl08KXqEP M9vZR/iAlXjwEU7g69SpYx+C4E72TiPbs3C3/SbPS8GNEbvRelgUmBOSD2dkhMcyMSQJXX z/LZs+Y94X5yqxr8m7mPWF8E3BEEZkk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-325-u8YTsZ1OPx-JFsue6E5txA-1; Wed, 16 Dec 2020 09:13:46 -0500 X-MC-Unique: u8YTsZ1OPx-JFsue6E5txA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C80AF100C60A; Wed, 16 Dec 2020 14:13:44 +0000 (UTC) Received: from t480s.redhat.com (ovpn-115-49.ams2.redhat.com [10.36.115.49]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1985160C15; Wed, 16 Dec 2020 14:13:41 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Subject: [PATCH v3 06/10] vfio: Support for RamDiscardMgr in the vIOMMU case Date: Wed, 16 Dec 2020 15:11:56 +0100 Message-Id: <20201216141200.118742-7-david@redhat.com> In-Reply-To: <20201216141200.118742-1-david@redhat.com> References: <20201216141200.118742-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="US-ASCII" Received-SPF: pass client-ip=216.205.24.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Pankaj Gupta , Wei Yang , David Hildenbrand , "Michael S. Tsirkin" , "Dr . David Alan Gilbert" , Peter Xu , Marek Kedzierski , Auger Eric , Alex Williamson , teawater , Jonathan Cameron , Paolo Bonzini , Igor Mammedov Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" vIOMMU support works already with RamDiscardMgr as long as guests only map populated memory. Both, populated and discarded memory is mapped into &address_space_memory, where vfio_get_xlat_addr() will find that memory, to create the vfio mapping. Sane guests will never map discarded memory (e.g., unplugged memory blocks in virtio-mem) into an IOMMU - or keep it mapped into an IOMMU while memory is getting discarded. However, there are two cases where a malicious guests could trigger pinning of more memory than intended. One case is easy to handle: the guest trying to map discarded memory into an IOMMU. The other case is harder to handle: the guest keeping memory mapped in the IOMMU while it is getting discarded. We would have to walk over all mappings when discarding memory and identify if any mapping would be a violation. Let's keep it simple for now and print a warning, indicating that setting RLIMIT_MEMLOCK can mitigate such attacks. We have to take care of incoming migration: at the point the IOMMUs get restored and start creating mappings in vfio, RamDiscardMgr implementations might not be back up and running yet. Let's rely on the runstate. An alternative would be using vmstate priorities - but current handling is cleaner and more obvious. Cc: Paolo Bonzini Cc: "Michael S. Tsirkin" Cc: Alex Williamson Cc: Dr. David Alan Gilbert Cc: Igor Mammedov Cc: Pankaj Gupta Cc: Peter Xu Cc: Auger Eric Cc: Wei Yang Cc: teawater Cc: Marek Kedzierski Signed-off-by: David Hildenbrand --- hw/vfio/common.c | 35 +++++++++++++++++++++++++++++++++++ hw/virtio/virtio-mem.c | 1 + include/migration/vmstate.h | 1 + 3 files changed, 37 insertions(+) diff --git a/hw/vfio/common.c b/hw/vfio/common.c index b1582be1e8..57c83a2f14 100644 --- a/hw/vfio/common.c +++ b/hw/vfio/common.c @@ -36,6 +36,7 @@ #include "qemu/range.h" #include "sysemu/kvm.h" #include "sysemu/reset.h" +#include "sysemu/runstate.h" #include "trace.h" #include "qapi/error.h" #include "migration/migration.h" @@ -595,6 +596,40 @@ static bool vfio_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr, error_report("iommu map to non memory area %"HWADDR_PRIx"", xlat); return false; + } else if (memory_region_has_ram_discard_mgr(mr)) { + RamDiscardMgr *rdm = memory_region_get_ram_discard_mgr(mr); + RamDiscardMgrClass *rdmc = RAM_DISCARD_MGR_GET_CLASS(rdm); + + /* + * Malicious VMs can map memory into the IOMMU, which is expected + * to remain discarded. vfio will pin all pages, populating memory. + * Disallow that. vmstate priorities make sure any RamDiscardMgr were + * already restored before IOMMUs are restored. + */ + if (!rdmc->is_populated(rdm, mr, xlat, len)) { + error_report("iommu map to discarded memory (e.g., unplugged via" + " virtio-mem): %"HWADDR_PRIx"", + iotlb->translated_addr); + return false; + } + + /* + * Malicious VMs might trigger discarding of IOMMU-mapped memory. The + * pages will remain pinned inside vfio until unmapped, resulting in a + * higher memory consumption than expected. If memory would get + * populated again later, there would be an inconsistency between pages + * pinned by vfio and pages seen by QEMU. This is the case until + * unmapped from the IOMMU (e.g., during device reset). + * + * With malicious guests, we really only care about pinning more memory + * than expected. RLIMIT_MEMLOCK set for the user/process can never be + * exceeded and can be used to mitigate this problem. + */ + warn_report_once("Using vfio with vIOMMUs and coordinated discarding of" + " RAM (e.g., virtio-mem) works, however, malicious" + " guests can trigger pinning of more memory than" + " intended via an IOMMU. It's possible to mitigate " + " by setting/adjusting RLIMIT_MEMLOCK."); } /* diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c index 6200813bb8..f419a758f3 100644 --- a/hw/virtio/virtio-mem.c +++ b/hw/virtio/virtio-mem.c @@ -871,6 +871,7 @@ static const VMStateDescription vmstate_virtio_mem_device = { .name = "virtio-mem-device", .minimum_version_id = 1, .version_id = 1, + .priority = MIG_PRI_VIRTIO_MEM, .post_load = virtio_mem_post_load, .fields = (VMStateField[]) { VMSTATE_WITH_TMP(VirtIOMEM, VirtIOMEMMigSanityChecks, diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h index 4d71dc8fba..5b0e930144 100644 --- a/include/migration/vmstate.h +++ b/include/migration/vmstate.h @@ -153,6 +153,7 @@ typedef enum { MIG_PRI_DEFAULT = 0, MIG_PRI_IOMMU, /* Must happen before PCI devices */ MIG_PRI_PCI_BUS, /* Must happen before IOMMU */ + MIG_PRI_VIRTIO_MEM, /* Must happen before IOMMU */ MIG_PRI_GICV3_ITS, /* Must happen before PCI devices */ MIG_PRI_GICV3, /* Must happen before the ITS */ MIG_PRI_MAX, -- 2.29.2