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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1F54DC433F5 for ; Tue, 4 Jan 2022 05:23:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229577AbiADFXs (ORCPT ); Tue, 4 Jan 2022 00:23:48 -0500 Received: from mga06.intel.com ([134.134.136.31]:55289 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230071AbiADFXr (ORCPT ); Tue, 4 Jan 2022 00:23:47 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1641273827; x=1672809827; h=cc:subject:to:references:from:message-id:date: mime-version:in-reply-to:content-transfer-encoding; bh=uXKPyRWOnxNU5FJs1OVLLK8xkyzVa8K8E1f+yzjqR1k=; b=K7kmWI0+BmIMTL172ZO1Kzbt9oorCc1+11QIYhH8qb0AcyWp9aIqKafa ELlNynP5lec9UwxhOuSreWdAryLstqtKsOdLAGjzdjJrPxf0xFl2/ocHx pbVr4m5ttj7NK9YLIYQgMMMHeqImV+pGSQZcnID4B845AfhiDWdcUbcau EGdCD6v3Yg0UZAwIiRex+u8BynLyDxdHmZNsOkN3pQfyMqweR3lo2R//h ebtLGqSqeZ62eMyZ1wn//Di2+PdL2T/H5Qu9uoWYg0HUbfjtbui30X5hG LZwsk2tqCjwJ5r8u9deCdorO6cnnsbvOYI3XtRHyUg4y2/PNcyXmpF7QB w==; X-IronPort-AV: E=McAfee;i="6200,9189,10216"; a="302911991" X-IronPort-AV: E=Sophos;i="5.88,260,1635231600"; d="scan'208";a="302911991" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Jan 2022 21:23:46 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,260,1635231600"; d="scan'208";a="525866862" Received: from allen-box.sh.intel.com (HELO [10.239.159.118]) ([10.239.159.118]) by orsmga008.jf.intel.com with ESMTP; 03 Jan 2022 21:23:39 -0800 Cc: baolu.lu@linux.intel.com, 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 Subject: Re: [PATCH v4 00/13] Fix BUG_ON in vfio_iommu_group_notifier() To: Greg Kroah-Hartman , Joerg Roedel , Alex Williamson , Bjorn Helgaas , Jason Gunthorpe , Christoph Hellwig , Kevin Tian , Ashok Raj References: <20211217063708.1740334-1-baolu.lu@linux.intel.com> From: Lu Baolu Message-ID: Date: Tue, 4 Jan 2022 13:23:02 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20211217063708.1740334-1-baolu.lu@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On 12/17/21 2:36 PM, Lu Baolu wrote: > Hi folks, > > The iommu group is the minimal isolation boundary for DMA. Devices in > a group can access each other's MMIO registers via peer to peer DMA > and also need share the same I/O address space. > > Once the I/O address space is assigned to user control it is no longer > available to the dma_map* API, which effectively makes the DMA API > non-working. > > Second, userspace can use DMA initiated by a device that it controls > to access the MMIO spaces of other devices in the group. This allows > userspace to indirectly attack any kernel owned device and it's driver. > > Therefore groups must either be entirely under kernel control or > userspace control, never a mixture. Unfortunately some systems have > problems with the granularity of groups and there are a couple of > important exceptions: > > - pci_stub allows the admin to block driver binding on a device and > make it permanently shared with userspace. Since PCI stub does not > do DMA it is safe, however the admin must understand that using > pci_stub allows userspace to attack whatever device it was bound > it. > > - PCI bridges are sometimes included in groups. Typically PCI bridges > do not use DMA, and generally do not have MMIO regions. > > Generally any device that does not have any MMIO registers is a > possible candidate for an exception. > > Currently vfio adopts a workaround to detect violations of the above > restrictions by monitoring the driver core BOUND event, and hardwiring > the above exceptions. Since there is no way for vfio to reject driver > binding at this point, BUG_ON() is triggered if a violation is > captured (kernel driver BOUND event on a group which already has some > devices assigned to userspace). Aside from the bad user experience > this opens a way for root userspace to crash the kernel, even in high > integrity configurations, by manipulating the module binding and > triggering the BUG_ON. > > This series solves this problem by making the user/kernel ownership a > core concept at the IOMMU layer. The driver core enforces kernel > ownership while drivers are bound and violations now result in a error > codes during probe, not BUG_ON failures. > > Patch partitions: > [PATCH 1-4]: Detect DMA ownership conflicts during driver binding; > [PATCH 5-8]: Add security context management for assigned devices; > [PATCH 9-13]: Various cleanups. > > This is also part one of three initial series for IOMMUFD: > * Move IOMMU Group security into the iommu layer > - Generic IOMMUFD implementation > - VFIO ability to consume IOMMUFD > > Change log: > v1: initial post > - https://lore.kernel.org/linux-iommu/20211115020552.2378167-1-baolu.lu@linux.intel.com/ > > v2: > - https://lore.kernel.org/linux-iommu/20211128025051.355578-1-baolu.lu@linux.intel.com/ > > - Move kernel dma ownership auto-claiming from driver core to bus > callback. [Greg/Christoph/Robin/Jason] > https://lore.kernel.org/linux-iommu/20211115020552.2378167-1-baolu.lu@linux.intel.com/T/#m153706912b770682cb12e3c28f57e171aa1f9d0c > > - Code and interface refactoring for iommu_set/release_dma_owner() > interfaces. [Jason] > https://lore.kernel.org/linux-iommu/20211115020552.2378167-1-baolu.lu@linux.intel.com/T/#mea70ed8e4e3665aedf32a5a0a7db095bf680325e > > - [NEW]Add new iommu_attach/detach_device_shared() interfaces for > multiple devices group. [Robin/Jason] > https://lore.kernel.org/linux-iommu/20211115020552.2378167-1-baolu.lu@linux.intel.com/T/#mea70ed8e4e3665aedf32a5a0a7db095bf680325e > > - [NEW]Use iommu_attach/detach_device_shared() in drm/tegra drivers. > > - Refactoring and description refinement. > > v3: > - https://lore.kernel.org/linux-iommu/20211206015903.88687-1-baolu.lu@linux.intel.com/ > > - Rename bus_type::dma_unconfigure to bus_type::dma_cleanup. [Greg] > https://lore.kernel.org/linux-iommu/c3230ace-c878-39db-1663-2b752ff5384e@linux.intel.com/T/#m6711e041e47cb0cbe3964fad0a3466f5ae4b3b9b > > - Avoid _platform_dma_configure for platform_bus_type::dma_configure. > [Greg] > https://lore.kernel.org/linux-iommu/c3230ace-c878-39db-1663-2b752ff5384e@linux.intel.com/T/#m43fc46286611aa56a5c0eeaad99d539e5519f3f6 > > - Patch "0012-iommu-Add-iommu_at-de-tach_device_shared-for-mult.patch" > and "0018-drm-tegra-Use-the-iommu-dma_owner-mechanism.patch" have > been tested by Dmitry Osipenko . > > v4: > - Remove unnecessary tegra->domain chech in the tegra patch. (Jason) > - Remove DMA_OWNER_NONE. (Joerg) > - Change refcount to unsigned int. (Christoph) > - Move mutex lock into group set_dma_owner functions. (Christoph) > - Add kernel doc for iommu_attach/detach_domain_shared(). (Christoph) > - Move dma auto-claim into driver core. (Jason/Christoph) Thank you very much for the review comments. A new version has been posted. https://lore.kernel.org/linux-iommu/20220104015644.2294354-1-baolu.lu@linux.intel.com/ Best regards, baolu