mbox series

[v15,00/12] Restricted DMA

Message ID 20210624155526.2775863-1-tientzu@chromium.org (mailing list archive)
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Series Restricted DMA | expand

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Claire Chang June 24, 2021, 3:55 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

v15:
- Apply Will's diff (https://lore.kernel.org/patchwork/patch/1448957/#1647521)
  to fix the crash reported by Qian.
- Add Stefano's Acked-by tag for patch 01/12 from v14

v14:
- Move set_memory_decrypted before swiotlb_init_io_tlb_mem (patch 01/12, 10,12)
- Add Stefano's Acked-by tag from v13
https://lore.kernel.org/patchwork/cover/1448954/

v13:
- Fix xen-swiotlb issues
  - memset in patch 01/12
  - is_swiotlb_force_bounce in patch 06/12
- Fix the dts example typo in reserved-memory.txt
- Add Stefano and Will's Tested-by tag from v12
https://lore.kernel.org/patchwork/cover/1448001/

v12:
Split is_dev_swiotlb_force into is_swiotlb_force_bounce (patch 06/12) and
is_swiotlb_for_alloc (patch 09/12)
https://lore.kernel.org/patchwork/cover/1447254/

v11:
- Rebase against swiotlb devel/for-linus-5.14
- s/mempry/memory/g
- exchange the order of patch 09/12 and 10/12
https://lore.kernel.org/patchwork/cover/1447216/

v10:
Address the comments in v9 to
  - fix the dev->dma_io_tlb_mem assignment
  - propagate swiotlb_force setting into io_tlb_default_mem->force
  - move set_memory_decrypted out of swiotlb_init_io_tlb_mem
  - move debugfs_dir declaration into the main CONFIG_DEBUG_FS block
  - add swiotlb_ prefix to find_slots and release_slots
  - merge the 3 alloc/free related patches
  - move the CONFIG_DMA_RESTRICTED_POOL later
https://lore.kernel.org/patchwork/cover/1446882/

v9:
Address the comments in v7 to
  - set swiotlb active pool to dev->dma_io_tlb_mem
  - get rid of get_io_tlb_mem
  - dig out the device struct for is_swiotlb_active
  - move debugfs_create_dir out of swiotlb_create_debugfs
  - do set_memory_decrypted conditionally in swiotlb_init_io_tlb_mem
  - use IS_ENABLED in kernel/dma/direct.c
  - fix redefinition of 'of_dma_set_restricted_buffer'
https://lore.kernel.org/patchwork/cover/1445081/

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.
https://lore.kernel.org/patchwork/cover/1437112/

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 (12):
  swiotlb: Refactor swiotlb init functions
  swiotlb: Refactor swiotlb_create_debugfs
  swiotlb: Set dev->dma_io_tlb_mem to the swiotlb pool used
  swiotlb: Update is_swiotlb_buffer to add a struct device argument
  swiotlb: Update is_swiotlb_active to add a struct device argument
  swiotlb: Use is_swiotlb_force_bounce for swiotlb data bouncing
  swiotlb: Move alloc_size to swiotlb_find_slots
  swiotlb: Refactor swiotlb_tbl_unmap_single
  swiotlb: Add restricted DMA alloc/free support
  swiotlb: Add restricted DMA pool initialization
  dt-bindings: of: Add restricted DMA pool
  of: Add plumbing for restricted DMA pool

 .../reserved-memory/reserved-memory.txt       |  36 ++-
 drivers/base/core.c                           |   4 +
 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                          |  33 +++
 drivers/of/device.c                           |   3 +
 drivers/of/of_private.h                       |   6 +
 drivers/pci/xen-pcifront.c                    |   2 +-
 drivers/xen/swiotlb-xen.c                     |   4 +-
 include/linux/device.h                        |   4 +
 include/linux/swiotlb.h                       |  53 +++-
 kernel/dma/Kconfig                            |  14 +
 kernel/dma/direct.c                           |  59 ++--
 kernel/dma/direct.h                           |   8 +-
 kernel/dma/swiotlb.c                          | 251 +++++++++++++-----
 16 files changed, 390 insertions(+), 103 deletions(-)

Comments

Konrad Rzeszutek Wilk June 24, 2021, 7:19 p.m. UTC | #1 
On Thu, Jun 24, 2021 at 11:55:14PM +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
> 
> v15:
> - Apply Will's diff (https://lore.kernel.org/patchwork/patch/1448957/#1647521)
>   to fix the crash reported by Qian.
> - Add Stefano's Acked-by tag for patch 01/12 from v14

That all should be now be on

https://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb.git/
devel/for-linus-5.14 (and linux-next)
Claire Chang June 25, 2021, 12:41 a.m. UTC | #2 
On Fri, Jun 25, 2021 at 3:20 AM Konrad Rzeszutek Wilk
<konrad.wilk@oracle.com> wrote:
>
> On Thu, Jun 24, 2021 at 11:55:14PM +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
> >
> > v15:
> > - Apply Will's diff (https://lore.kernel.org/patchwork/patch/1448957/#1647521)
> >   to fix the crash reported by Qian.
> > - Add Stefano's Acked-by tag for patch 01/12 from v14
>
> That all should be now be on
>
> https://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb.git/
> devel/for-linus-5.14 (and linux-next)
>

devel/for-linus-5.14 looks good. Thanks!
Will Deacon June 25, 2021, 12:30 p.m. UTC | #3 
On Thu, Jun 24, 2021 at 03:19:48PM -0400, Konrad Rzeszutek Wilk wrote:
> On Thu, Jun 24, 2021 at 11:55:14PM +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
> > 
> > v15:
> > - Apply Will's diff (https://lore.kernel.org/patchwork/patch/1448957/#1647521)
> >   to fix the crash reported by Qian.
> > - Add Stefano's Acked-by tag for patch 01/12 from v14
> 
> That all should be now be on
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb.git/
> devel/for-linus-5.14 (and linux-next)

Thanks Konrad!

Will