dma-mapping: move dma_map_resource() sanity check into debug code

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Summary

CVECVE-2026-64149
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:56 UTC
Updated2026-07-19 16:17:56 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: dma-mapping: move dma_map_resource() sanity check into debug code dma_map_resource() uses pfn_valid() to ensure the range is not RAM. However, pfn_valid() only checks for availability of the memory map for a PFN but it does not ensure that the PFN is actually backed by RAM. On ARM64 with SPARSEMEM (128MB section granularity), MMIO addresses that share a section with RAM will falsely trigger the WARN_ON_ONCE and cause dma_map_resource() to return DMA_MAPPING_ERROR. This causes a WARNING on Raspberry Pi 4 during spi_bcm2835 probe because the SPI FIFO register (0xfe204004) falls in the same sparsemem section as the end of RAM (0xf8000000-0xfbffffff), both in section 31 (0xf8000000-0xffffffff). Move the sanity check from dma_map_resource() into debug_dma_map_phys() and replace the unreliable pfn_valid() with pfn_valid() && !PageReserved(), which correctly identifies actual usable RAM without false positives for MMIO regions that happen to have struct pages. Since dma_map_resource() is dma_map_phys(DMA_ATTR_MMIO), the check applies equally to both APIs. Any non-reserved page represents kernel memory to a sufficient degree that using DMA_ATTR_MMIO on it is almost certainly wrong and risks breaking coherency on non-coherent platforms. ZONE_DEVICE pages used for PCI P2P DMA (MEMORY_DEVICE_PCI_P2PDMA) have PageReserved set, so they will not trigger a false positive. The check no longer blocks the mapping and uses err_printk() to integrate with dma-debug filtering.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected f7326196a781622b33bfbdabb00f5e72b5fb5679 181e67bc11c5ec5b87c6c512c2078752b23ca8d4 git Not specified
CNA Linux Linux affected f7326196a781622b33bfbdabb00f5e72b5fb5679 004a777879ff629f6e0ca3d09ad09fa3452bcc4d git Not specified
CNA Linux Linux affected f7326196a781622b33bfbdabb00f5e72b5fb5679 af0c3f05866237f7592219bfe05387bc3bfc99b5 git Not specified
CNA Linux Linux affected 6.18 Not specified
CNA Linux Linux unaffected 6.18 semver Not specified
CNA Linux Linux unaffected 6.18.34 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.11 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/004a777879ff629f6e0ca3d09ad09fa3452bcc4d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/181e67bc11c5ec5b87c6c512c2078752b23ca8d4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/af0c3f05866237f7592219bfe05387bc3bfc99b5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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