[v8,00/15] Restricted DMA

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.

v7:
Fix debugfs, PageHighMem and comment style in rmem_swiotlb_device_init
https://lore.kernel.org/patchwork/cover/1431031/

v6:
Address the comments in v5
https://lore.kernel.org/patchwork/cover/1423201/

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/

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       |  36 ++-
 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, 362 insertions(+), 100 deletions(-)

I just finished reviewing v7, sorry.  Let me find some time to see what
difference this version makes.

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 <will@kernel.org>

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

On Sat, Jun 5, 2021 at 1:48 AM Will Deacon <will@kernel.org> wrote:
>
> 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 <will@kernel.org>
>
> 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.

Thanks for testing.

Christoph also added some comments in v7, so I'll prepare v9.

>
> Cheers,
>
> Will

v9 here: https://lore.kernel.org/patchwork/cover/1445081/

On Mon, Jun 7, 2021 at 11:28 AM Claire Chang <tientzu@chromium.org> wrote:
>
> On Sat, Jun 5, 2021 at 1:48 AM Will Deacon <will@kernel.org> wrote:
> >
> > 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 <will@kernel.org>
> >
> > 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.
>
> Thanks for testing.
>
> Christoph also added some comments in v7, so I'll prepare v9.
>
> >
> > Cheers,
> >
> > Will