CVE-2026-64149

Summary

In 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.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/181e67bc11c5ec5b87c6c512c2078752b23ca8d4
• https://git.kernel.org/stable/c/004a777879ff629f6e0ca3d09ad09fa3452bcc4d
• https://git.kernel.org/stable/c/af0c3f05866237f7592219bfe05387bc3bfc99b5

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