linux-kernel - Re: [PATCH v14 00/12] Restricted DMA

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Message-ID: <YNLy7z0Zq1AXKLng@char.us.oracle.com>
Date:   Wed, 23 Jun 2021 04:38:07 -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>,
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        benh@...nel.crashing.org, paulus@...ba.org,
        "list@....net:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
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Subject: Re: [PATCH v14 00/12] Restricted DMA

On Sat, Jun 19, 2021 at 11:40:31AM +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

Heya Claire,

I put all your patches on
https://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb.git/log/?h=devel/for-linus-5.14

Please double-check that they all look ok.

Thank you!