Re: [PATCH v6 00/15] Restricted DMA

[Claire Chang <tientzu@chromium.org>]

v7: https://lore.kernel.org/patchwork/cover/1431031/

On Mon, May 10, 2021 at 5:50 PM Claire Chang <tientzu@chromium.org> wrote:
>
> From: Claire Chang <tientzu@google.com>
>
> 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
>
> v6:
> Address the comments in v5
>
> v5:
> Rebase on latest linux-next
> https://lore.kernel.org/patchwork/cover/1416899/
>
> v4:
> - Fix spinlock bad magic
> - Use rmem->name for debugfs entry
> - Address the comments in v3
> https://lore.kernel.org/patchwork/cover/1378113/
>
> v3:
> Using only one reserved memory region for both streaming DMA and memory
> allocation.
> https://lore.kernel.org/patchwork/cover/1360992/
>
> v2:
> Building on top of swiotlb.
> https://lore.kernel.org/patchwork/cover/1280705/
>
> v1:
> Using dma_map_ops.
> https://lore.kernel.org/patchwork/cover/1271660/
> *** BLURB HERE ***
>
> Claire Chang (15):
>   swiotlb: Refactor swiotlb init functions
>   swiotlb: Refactor swiotlb_create_debugfs
>   swiotlb: Add DMA_RESTRICTED_POOL
>   swiotlb: Add restricted DMA pool initialization
>   swiotlb: Add a new get_io_tlb_mem getter
>   swiotlb: Update is_swiotlb_buffer to add a struct device argument
>   swiotlb: Update is_swiotlb_active to add a struct device argument
>   swiotlb: Bounce data from/to restricted DMA pool if available
>   swiotlb: Move alloc_size to find_slots
>   swiotlb: Refactor swiotlb_tbl_unmap_single
>   dma-direct: Add a new wrapper __dma_direct_free_pages()
>   swiotlb: Add restricted DMA alloc/free support.
>   dma-direct: Allocate memory from restricted DMA pool if available
>   dt-bindings: of: Add restricted DMA pool
>   of: Add plumbing for restricted DMA pool
>
>  .../reserved-memory/reserved-memory.txt       |  27 ++
>  drivers/gpu/drm/i915/gem/i915_gem_internal.c  |   2 +-
>  drivers/gpu/drm/nouveau/nouveau_ttm.c         |   2 +-
>  drivers/iommu/dma-iommu.c                     |  12 +-
>  drivers/of/address.c                          |  25 ++
>  drivers/of/device.c                           |   3 +
>  drivers/of/of_private.h                       |   5 +
>  drivers/pci/xen-pcifront.c                    |   2 +-
>  drivers/xen/swiotlb-xen.c                     |   2 +-
>  include/linux/device.h                        |   4 +
>  include/linux/swiotlb.h                       |  41 ++-
>  kernel/dma/Kconfig                            |  14 +
>  kernel/dma/direct.c                           |  63 +++--
>  kernel/dma/direct.h                           |   9 +-
>  kernel/dma/swiotlb.c                          | 242 +++++++++++++-----
>  15 files changed, 356 insertions(+), 97 deletions(-)
>
> --
> 2.31.1.607.g51e8a6a459-goog
>