dma-mapping: truncate dma masks to what dma_addr_t can hold (4a54d16f) · Commits · 戴 / test

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: ("Documentation/DMA-API-HOWTO: update dma_mask sections") Signed-off-by:

Christoph Hellwig <hch@lst.de>

kernel/dma/mapping.c

+12 −0

Original line number	Diff line number	Diff line
		@@ -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;

		@@ -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;

Admin message