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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 5BCBAC43381 for ; Mon, 1 Apr 2019 20:16:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 31C4F20896 for ; Mon, 1 Apr 2019 20:16:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726867AbfDAUQ5 (ORCPT ); Mon, 1 Apr 2019 16:16:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52924 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726284AbfDAUQ5 (ORCPT ); Mon, 1 Apr 2019 16:16:57 -0400 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 mx1.redhat.com (Postfix) with ESMTPS id 6BC20307D933; Mon, 1 Apr 2019 20:16:57 +0000 (UTC) Received: from gimli.home (ovpn-116-99.phx2.redhat.com [10.3.116.99]) by smtp.corp.redhat.com (Postfix) with ESMTP id AF2DC104C53F; Mon, 1 Apr 2019 20:16:52 +0000 (UTC) Subject: [PATCH] vfio/type1: Limit DMA mappings per container From: Alex Williamson To: alex.williamson@redhat.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, eric.auger@redhat.com, cohuck@redhat.com Date: Mon, 01 Apr 2019 14:16:52 -0600 Message-ID: <155414977872.12780.13728555131525362206.stgit@gimli.home> User-Agent: StGit/0.19-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.48]); Mon, 01 Apr 2019 20:16:57 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Archived-At: List-Archive: List-Post: Memory backed DMA mappings are accounted against a user's locked memory limit, including multiple mappings of the same memory. This accounting bounds the number of such mappings that a user can create. However, DMA mappings that are not backed by memory, such as DMA mappings of device MMIO via mmaps, do not make use of page pinning and therefore do not count against the user's locked memory limit. These mappings still consume memory, but the memory is not well associated to the process for the purpose of oom killing a task. To add bounding on this use case, we introduce a limit to the total number of concurrent DMA mappings that a user is allowed to create. This limit is exposed as a tunable module option where the default value of 64K is expected to be well in excess of any reasonable use case (a large virtual machine configuration would typically only make use of tens of concurrent mappings). This fixes CVE-2019-3882. Signed-off-by: Alex Williamson --- drivers/vfio/vfio_iommu_type1.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index 73652e21efec..7fc8fd7d4dc7 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -58,12 +58,18 @@ module_param_named(disable_hugepages, MODULE_PARM_DESC(disable_hugepages, "Disable VFIO IOMMU support for IOMMU hugepages."); +static int dma_entry_limit __read_mostly = U16_MAX; +module_param_named(dma_entry_limit, dma_entry_limit, int, 0644); +MODULE_PARM_DESC(dma_entry_limit, + "Maximum number of user DMA mappings per container (65535)."); + struct vfio_iommu { struct list_head domain_list; struct vfio_domain *external_domain; /* domain for external user */ struct mutex lock; struct rb_root dma_list; struct blocking_notifier_head notifier; + atomic_t dma_avail; bool v2; bool nesting; }; @@ -836,6 +842,7 @@ static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma) vfio_unlink_dma(iommu, dma); put_task_struct(dma->task); kfree(dma); + atomic_inc(&iommu->dma_avail); } static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu) @@ -1081,8 +1088,14 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu, goto out_unlock; } + if (!atomic_add_unless(&iommu->dma_avail, -1, 0)) { + ret = -ENOSPC; + goto out_unlock; + } + dma = kzalloc(sizeof(*dma), GFP_KERNEL); if (!dma) { + atomic_inc(&iommu->dma_avail); ret = -ENOMEM; goto out_unlock; } @@ -1583,6 +1596,7 @@ static void *vfio_iommu_type1_open(unsigned long arg) INIT_LIST_HEAD(&iommu->domain_list); iommu->dma_list = RB_ROOT; + atomic_set(&iommu->dma_avail, dma_entry_limit); mutex_init(&iommu->lock); BLOCKING_INIT_NOTIFIER_HEAD(&iommu->notifier);