From patchwork Fri Dec 17 06:36:59 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Baolu Lu X-Patchwork-Id: 12683751 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 11A3FC4332F for ; Fri, 17 Dec 2021 06:38:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233341AbhLQGiL (ORCPT ); Fri, 17 Dec 2021 01:38:11 -0500 Received: from mga17.intel.com ([192.55.52.151]:27206 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233344AbhLQGiK (ORCPT ); Fri, 17 Dec 2021 01:38:10 -0500 X-IronPort-AV: E=McAfee;i="6200,9189,10200"; a="220373966" X-IronPort-AV: E=Sophos;i="5.88,213,1635231600"; d="scan'208";a="220373966" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Dec 2021 22:38:09 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,213,1635231600"; d="scan'208";a="519623208" Received: from allen-box.sh.intel.com ([10.239.159.118]) by orsmga008.jf.intel.com with ESMTP; 16 Dec 2021 22:37:57 -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 , Dmitry Osipenko , iommu@lists.linux-foundation.org, linux-pci@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Lu Baolu Subject: [PATCH v4 04/13] PCI: portdrv: Suppress kernel DMA ownership auto-claiming Date: Fri, 17 Dec 2021 14:36:59 +0800 Message-Id: <20211217063708.1740334-5-baolu.lu@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211217063708.1740334-1-baolu.lu@linux.intel.com> References: <20211217063708.1740334-1-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 | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c index 35eca6277a96..c48a8734f9c4 100644 --- a/drivers/pci/pcie/portdrv_pci.c +++ b/drivers/pci/pcie/portdrv_pci.c @@ -202,7 +202,10 @@ static struct pci_driver pcie_portdriver = { .err_handler = &pcie_portdrv_err_handler, - .driver.pm = PCIE_PORTDRV_PM_OPS, + .driver = { + .pm = PCIE_PORTDRV_PM_OPS, + .suppress_auto_claim_dma_owner = true, + }, }; static int __init dmi_pcie_pme_disable_msi(const struct dmi_system_id *d)