Re: [PATCH v14 00/12] Restricted DMA

[Claire Chang]

On Wed, Jun 23, 2021 at 4:38 PM Konrad Rzeszutek Wilk
<konrad.wilk@xxxxxxxxxx> wrote:
>
> 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!

They look fine. Thank you!