From patchwork Thu Jan 21 11:05:36 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 1429745 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=eN6h491R; dkim-atps=neutral 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 ozlabs.org (Postfix) with ESMTPS id 4DM0D66HG3z9sTD for ; Thu, 21 Jan 2021 22:15:02 +1100 (AEDT) Received: from localhost ([::1]:56216 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l2XvY-0000Ux-Q8 for incoming@patchwork.ozlabs.org; Thu, 21 Jan 2021 06:15:00 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:47318) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l2XoA-00075d-N5 for qemu-devel@nongnu.org; Thu, 21 Jan 2021 06:07:22 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:33132) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l2Xo8-0006xr-Qb for qemu-devel@nongnu.org; Thu, 21 Jan 2021 06:07:22 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611227240; 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=om82tgrTyj4Etrzelc2u27W0a4C4YtCKKXce7HP1CtA=; b=eN6h491RdSgXRaBHGUnWJnPlc8lSV+jLF+dahHWeP9M5GEHWOZy7Vp917kayvCFRbou1Kt pqHOjODsvTHMYbmzkx89b1BIu4Yx3Uyidhzd5S5FCm5E62WEi+BJLfgC08Rp6OTHCwp5AY Ds6SO56WLsXauh9r31VR17zITdnKwxQ= 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-79-PmZoNs40OzaD3dlamatJwA-1; Thu, 21 Jan 2021 06:07:17 -0500 X-MC-Unique: PmZoNs40OzaD3dlamatJwA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3FC41800D55; Thu, 21 Jan 2021 11:07:16 +0000 (UTC) Received: from t480s.redhat.com (ovpn-115-70.ams2.redhat.com [10.36.115.70]) by smtp.corp.redhat.com (Postfix) with ESMTP id C386F100AE37; Thu, 21 Jan 2021 11:07:07 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Subject: [PATCH v5 07/11] vfio: Support for RamDiscardMgr in the vIOMMU case Date: Thu, 21 Jan 2021 12:05:36 +0100 Message-Id: <20210121110540.33704-8-david@redhat.com> In-Reply-To: <20210121110540.33704-1-david@redhat.com> References: <20210121110540.33704-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 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 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: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.167, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, 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+incoming=patchwork.ozlabs.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 add runstate priorities to enforce the order when restoring. 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 Acked-by: Alex Williamson Reviewed-by: Alex Williamson --- 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 166ec6ec62..15ecd05a4b 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" @@ -574,6 +575,40 @@ 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 075ee80096..3bf58ff043 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,