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dma-mapping: truncate dma masks to what dma_addr_t can hold
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The dma masks in struct device are always 64-bits wide.  But for builds
using a 32-bit dma_addr_t we need to ensure we don't store an
unsupportable value.  Before Linux 5.0 this was handled at least by
the ARM dma mapping code by never allowing to set a larger dma_mask,
but these days we allow the driver to just set the largest supported
value and never fall back to a smaller one.  Ensure this always works
by truncating the value.

Fixes: 9eb9e96 ("Documentation/DMA-API-HOWTO: update dma_mask sections")
Signed-off-by: Christoph Hellwig <hch@lst.de>
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Christoph Hellwig committed Jun 25, 2019
1 parent 591fcf3 commit 4a54d16
Showing 1 changed file with 12 additions and 0 deletions.
12 changes: 12 additions & 0 deletions kernel/dma/mapping.c
Original file line number Diff line number Diff line change
Expand Up @@ -317,6 +317,12 @@ void arch_dma_set_mask(struct device *dev, u64 mask);

int dma_set_mask(struct device *dev, u64 mask)
{
/*
* Truncate the mask to the actually supported dma_addr_t width to
* avoid generating unsupportable addresses.
*/
mask = (dma_addr_t)mask;

if (!dev->dma_mask || !dma_supported(dev, mask))
return -EIO;

Expand All @@ -330,6 +336,12 @@ EXPORT_SYMBOL(dma_set_mask);
#ifndef CONFIG_ARCH_HAS_DMA_SET_COHERENT_MASK
int dma_set_coherent_mask(struct device *dev, u64 mask)
{
/*
* Truncate the mask to the actually supported dma_addr_t width to
* avoid generating unsupportable addresses.
*/
mask = (dma_addr_t)mask;

if (!dma_supported(dev, mask))
return -EIO;

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