v11 https://lore.kernel.org/patchwork/cover/1447216/ On Tue, Jun 15, 2021 at 9:27 PM Claire Chang <tientzu@xxxxxxxxxxxx> 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 > > 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 > > 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_dev_swiotlb_force for swiotlb data bouncing > swiotlb: Move alloc_size to swiotlb_find_slots > swiotlb: Refactor swiotlb_tbl_unmap_single > swiotlb: Add restricted DMA pool initialization > swiotlb: Add restricted DMA alloc/free support > 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 | 2 +- > include/linux/device.h | 4 + > include/linux/swiotlb.h | 40 ++- > kernel/dma/Kconfig | 14 + > kernel/dma/direct.c | 60 +++-- > kernel/dma/direct.h | 8 +- > kernel/dma/swiotlb.c | 255 +++++++++++++----- > 16 files changed, 380 insertions(+), 103 deletions(-) > > -- > 2.32.0.272.g935e593368-goog >
