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dma-mapping fix for Linux 5.17

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- fix a swiotlb info leak (Halil Pasic)
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Merge tag 'dma-mapping-5.17-1' of git://git.infradead.org/users/hch/dma-mapping

Pull dma-mapping fix from Christoph Hellwig:

 - fix a swiotlb info leak (Halil Pasic)

* tag 'dma-mapping-5.17-1' of git://git.infradead.org/users/hch/dma-mapping:
  swiotlb: fix info leak with DMA_FROM_DEVICE
This commit is contained in:
Linus Torvalds 2022-02-27 12:42:37 -08:00
commit 98f3e84f8d
3 changed files with 18 additions and 1 deletions
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8
Documentation/core-api/dma-attributes.rst
View file

@ -130,3 +130,11 @@ accesses to DMA buffers in both privileged "supervisor" and unprivileged
subsystem that the buffer is fully accessible at the elevated privilege
level (and ideally inaccessible or at least read-only at the
lesser-privileged levels).
DMA_ATTR_OVERWRITE
------------------
This is a hint to the DMA-mapping subsystem that the device is expected to
overwrite the entire mapped size, thus the caller does not require any of the
previous buffer contents to be preserved. This allows bounce-buffering
implementations to optimise DMA_FROM_DEVICE transfers.

8
include/linux/dma-mapping.h
View file

@ -61,6 +61,14 @@
*/
#define DMA_ATTR_PRIVILEGED (1UL << 9)
/*
* This is a hint to the DMA-mapping subsystem that the device is expected
* to overwrite the entire mapped size, thus the caller does not require any
* of the previous buffer contents to be preserved. This allows
* bounce-buffering implementations to optimise DMA_FROM_DEVICE transfers.
*/
#define DMA_ATTR_OVERWRITE (1UL << 10)
/*
* A dma_addr_t can hold any valid DMA or bus address for the platform. It can
* be given to a device to use as a DMA source or target. It is specific to a

3
kernel/dma/swiotlb.c
View file

@ -628,7 +628,8 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
mem->slots[index + i].orig_addr = slot_addr(orig_addr, i);
tlb_addr = slot_addr(mem->start, index) + offset;
if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
(dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL))
(!(attrs & DMA_ATTR_OVERWRITE) || dir == DMA_TO_DEVICE ||
dir == DMA_BIDIRECTIONAL))
swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_TO_DEVICE);
return tlb_addr;
}