linux-kernel - Re: [PATCH v15 00/12] Restricted DMA

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Date:   Thu, 24 Jun 2021 15:19:48 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Claire Chang <tientzu@...omium.org>
Cc:     Rob Herring <robh+dt@...nel.org>, mpe@...erman.id.au,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        boris.ostrovsky@...cle.com, jgross@...e.com,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        benh@...nel.crashing.org, paulus@...ba.org,
        "list@....net:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        sstabellini@...nel.org, Robin Murphy <robin.murphy@....com>,
        grant.likely@....com, xypron.glpk@....de,
        Thierry Reding <treding@...dia.com>, mingo@...nel.org,
        bauerman@...ux.ibm.com, peterz@...radead.org,
        Greg KH <gregkh@...uxfoundation.org>,
        Saravana Kannan <saravanak@...gle.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        heikki.krogerus@...ux.intel.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        linux-devicetree <devicetree@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        linuxppc-dev@...ts.ozlabs.org, xen-devel@...ts.xenproject.org,
        Nicolas Boichat <drinkcat@...omium.org>,
        Jim Quinlan <james.quinlan@...adcom.com>, tfiga@...omium.org,
        bskeggs@...hat.com, bhelgaas@...gle.com, chris@...is-wilson.co.uk,
        daniel@...ll.ch, airlied@...ux.ie, dri-devel@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, jani.nikula@...ux.intel.com,
        jxgao@...gle.com, joonas.lahtinen@...ux.intel.com,
        linux-pci@...r.kernel.org, maarten.lankhorst@...ux.intel.com,
        matthew.auld@...el.com, rodrigo.vivi@...el.com,
        thomas.hellstrom@...ux.intel.com, thomas.lendacky@....com,
        quic_qiancai@...cinc.com
Subject: Re: [PATCH v15 00/12] Restricted DMA

On Thu, Jun 24, 2021 at 11:55:14PM +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
> 
> v15:
> - Apply Will's diff (https://lore.kernel.org/patchwork/patch/1448957/#1647521)
>   to fix the crash reported by Qian.
> - Add Stefano's Acked-by tag for patch 01/12 from v14

That all should be now be on

https://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb.git/
devel/for-linus-5.14 (and linux-next)