mbox series

[v8,00/15] Restricted DMA

Message ID 20210527125845.1852284-1-tientzu@chromium.org (mailing list archive)
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Series Restricted DMA | expand

Message

Claire Chang May 27, 2021, 12:58 p.m. UTC 
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(-)

Comments

Christoph Hellwig May 27, 2021, 1:32 p.m. UTC | #1 
I just finished reviewing v7, sorry.  Let me find some time to see what
difference this version makes.
Will Deacon June 4, 2021, 5:48 p.m. UTC | #2 
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
Claire Chang June 7, 2021, 3:28 a.m. UTC | #3 
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
Claire Chang June 11, 2021, 3:31 p.m. UTC | #4 
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