From patchwork Sun Nov 28 02:50:42 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Baolu Lu X-Patchwork-Id: 12642601 X-Patchwork-Delegate: bhelgaas@google.com 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 620CAC433F5 for ; Sun, 28 Nov 2021 02:54:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349935AbhK1C5P (ORCPT ); Sat, 27 Nov 2021 21:57:15 -0500 Received: from mga12.intel.com ([192.55.52.136]:14879 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239793AbhK1CzO (ORCPT ); Sat, 27 Nov 2021 21:55:14 -0500 X-IronPort-AV: E=McAfee;i="6200,9189,10181"; a="215825055" X-IronPort-AV: E=Sophos;i="5.87,270,1631602800"; d="scan'208";a="215825055" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Nov 2021 18:51:59 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.87,270,1631602800"; d="scan'208";a="652489040" Received: from allen-box.sh.intel.com ([10.239.159.118]) by fmsmga001.fm.intel.com with ESMTP; 27 Nov 2021 18:51:52 -0800 From: Lu Baolu To: Greg Kroah-Hartman , Joerg Roedel , Alex Williamson , Bjorn Helgaas , Jason Gunthorpe , Christoph Hellwig , Kevin Tian , Ashok Raj Cc: Will Deacon , Robin Murphy , Dan Williams , rafael@kernel.org, Diana Craciun , Cornelia Huck , Eric Auger , Liu Yi L , Jacob jun Pan , Chaitanya Kulkarni , Stuart Yoder , Laurentiu Tudor , Thierry Reding , David Airlie , Daniel Vetter , Jonathan Hunter , Li Yang , iommu@lists.linux-foundation.org, linux-pci@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Lu Baolu Subject: [PATCH v2 08/17] PCI: portdrv: Suppress kernel DMA ownership auto-claiming Date: Sun, 28 Nov 2021 10:50:42 +0800 Message-Id: <20211128025051.355578-9-baolu.lu@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211128025051.355578-1-baolu.lu@linux.intel.com> References: <20211128025051.355578-1-baolu.lu@linux.intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org IOMMU grouping on PCI necessitates that if we lack isolation on a bridge then all of the downstream devices will be part of the same IOMMU group as the bridge. The existing vfio framework allows the portdrv driver to be bound to the bridge while its downstream devices are assigned to user space. The pci_dma_configure() marks the iommu_group as containing only devices with kernel drivers that manage DMA. Avoid this default behavior for the portdrv driver in order for compatibility with the current vfio policy. The commit 5f096b14d421b ("vfio: Whitelist PCI bridges") extended above policy to all kernel drivers of bridge class. This is not always safe. For example, The shpchp_core driver relies on the PCI MMIO access for the controller functionality. With its downstream devices assigned to the userspace, the MMIO might be changed through user initiated P2P accesses without any notification. This might break the kernel driver integrity and lead to some unpredictable consequences. For any bridge driver, in order to avoiding default kernel DMA ownership claiming, we should consider: 1) Does the bridge driver use DMA? Calling pci_set_master() or a dma_map_* API is a sure indicate the driver is doing DMA 2) If the bridge driver uses MMIO, is it tolerant to hostile userspace also touching the same MMIO registers via P2P DMA attacks? Conservatively if the driver maps an MMIO region at all, we can say that it fails the test. Suggested-by: Jason Gunthorpe Suggested-by: Kevin Tian Signed-off-by: Lu Baolu --- drivers/pci/pcie/portdrv_pci.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c index 35eca6277a96..c66a83f2c987 100644 --- a/drivers/pci/pcie/portdrv_pci.c +++ b/drivers/pci/pcie/portdrv_pci.c @@ -202,6 +202,8 @@ static struct pci_driver pcie_portdriver = { .err_handler = &pcie_portdrv_err_handler, + .suppress_auto_claim_dma_owner = true, + .driver.pm = PCIE_PORTDRV_PM_OPS, };