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=-17.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 CD4DCC4743E for ; Fri, 4 Jun 2021 17:48:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B08426141B for ; Fri, 4 Jun 2021 17:48:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229878AbhFDRuR (ORCPT ); Fri, 4 Jun 2021 13:50:17 -0400 Received: from mail.kernel.org ([198.145.29.99]:37356 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229791AbhFDRuQ (ORCPT ); Fri, 4 Jun 2021 13:50:16 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D1B72611CE; Fri, 4 Jun 2021 17:48:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1622828909; bh=itHLj7KgFnb/FecADbuq7I4biuZGdUj1du28UW6T8SI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Iqm0inp9VgNpzeAFuP421rSsgCv0Qhkv5QnQPUkLUJFiTIxp7TFY3QR4OyPttmT96 63UJ1NvLjEWUu6sIeGlZQM4Ted9nVFpDXdWeD/OOk+ONJBJL5Ar0gZ0w9EXx03CeNz 9hxeLBPU+4Vs1Iu13rVy6icMo7fyuPwvCQ+cWk5bEidGKBw04BNS3wfiw4K6ZGCyPX 6cUjTh3kCX/N4K95NY0l8Alu5nPdSl//4dOSMljRD2azPbGNPTGPvDRtwrHFnkFOCZ c64/aftHtK6fT63h1C50fed28UcM2UZbSHegeAkgG/khU8kRyqVyIs14SrPvQtO8GW fslW9h7sjgBEQ== Date: Fri, 4 Jun 2021 18:48:18 +0100 From: Will Deacon To: Claire Chang Cc: Rob Herring , mpe@ellerman.id.au, Joerg Roedel , Frank Rowand , Konrad Rzeszutek Wilk , boris.ostrovsky@oracle.com, jgross@suse.com, Christoph Hellwig , Marek Szyprowski , benh@kernel.crashing.org, paulus@samba.org, "list@263.net:IOMMU DRIVERS" , sstabellini@kernel.org, Robin Murphy , grant.likely@arm.com, xypron.glpk@gmx.de, Thierry Reding , mingo@kernel.org, bauerman@linux.ibm.com, peterz@infradead.org, Greg KH , Saravana Kannan , "Rafael J . Wysocki" , heikki.krogerus@linux.intel.com, Andy Shevchenko , Randy Dunlap , Dan Williams , Bartosz Golaszewski , linux-devicetree , lkml , linuxppc-dev@lists.ozlabs.org, xen-devel@lists.xenproject.org, Nicolas Boichat , Jim Quinlan , tfiga@chromium.org, bskeggs@redhat.com, bhelgaas@google.com, chris@chris-wilson.co.uk, daniel@ffwll.ch, airlied@linux.ie, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, jani.nikula@linux.intel.com, jxgao@google.com, joonas.lahtinen@linux.intel.com, linux-pci@vger.kernel.org, maarten.lankhorst@linux.intel.com, matthew.auld@intel.com, rodrigo.vivi@intel.com, thomas.hellstrom@linux.intel.com Subject: Re: [PATCH v8 00/15] Restricted DMA Message-ID: <20210604174818.GC3703@willie-the-truck> References: <20210527125845.1852284-1-tientzu@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210527125845.1852284-1-tientzu@chromium.org> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi Claire, On Thu, May 27, 2021 at 08:58:30PM +0800, Claire Chang wrote: > This series implements mitigations for lack of DMA access control on > systems without an IOMMU, which could result in the DMA accessing the > system memory at unexpected times and/or unexpected addresses, possibly > leading to data leakage or corruption. > > For example, we plan to use the PCI-e bus for Wi-Fi and that PCI-e bus is > not behind an IOMMU. As PCI-e, by design, gives the device full access to > system memory, a vulnerability in the Wi-Fi firmware could easily escalate > to a full system exploit (remote wifi exploits: [1a], [1b] that shows a > full chain of exploits; [2], [3]). > > To mitigate the security concerns, we introduce restricted DMA. Restricted > DMA utilizes the existing swiotlb to bounce streaming DMA in and out of a > specially allocated region and does memory allocation from the same region. > The feature on its own provides a basic level of protection against the DMA > overwriting buffer contents at unexpected times. However, to protect > against general data leakage and system memory corruption, the system needs > to provide a way to restrict the DMA to a predefined memory region (this is > usually done at firmware level, e.g. MPU in ATF on some ARM platforms [4]). > > [1a] https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms-wi-fi_4.html > [1b] https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms-wi-fi_11.html > [2] https://blade.tencent.com/en/advisories/qualpwn/ > [3] https://www.bleepingcomputer.com/news/security/vulnerabilities-found-in-highly-popular-firmware-for-wifi-chips/ > [4] https://github.com/ARM-software/arm-trusted-firmware/blob/master/plat/mediatek/mt8183/drivers/emi_mpu/emi_mpu.c#L132 > > v8: > - Fix reserved-memory.txt and add the reg property in example. > - Fix sizeof for of_property_count_elems_of_size in > drivers/of/address.c#of_dma_set_restricted_buffer. > - Apply Will's suggestion to try the OF node having DMA configuration in > drivers/of/address.c#of_dma_set_restricted_buffer. > - Fix typo in the comment of drivers/of/address.c#of_dma_set_restricted_buffer. > - Add error message for PageHighMem in > kernel/dma/swiotlb.c#rmem_swiotlb_device_init and move it to > rmem_swiotlb_setup. > - Fix the message string in rmem_swiotlb_setup. Thanks for the v8. It works for me out of the box on arm64 under KVM, so: Tested-by: Will Deacon Note that something seems to have gone wrong with the mail threading, so the last 5 patches ended up as a separate thread for me. Probably worth posting again with all the patches in one place, if you can. Cheers, Will