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CVE-2026-64149

Estado: AnalizadaMedia (5.5)—

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).

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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.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndma-mapping: move dma_map_resource() sanity check into debug code\n\ndma_map_resource() uses pfn_valid() to ensure the range is not RAM.\nHowever, pfn_valid() only checks for availability of the memory map for\na PFN but it does not ensure that the PFN is actually backed by RAM. On\nARM64 with SPARSEMEM (128MB section granularity), MMIO addresses that\nshare a section with RAM will falsely trigger the WARN_ON_ONCE and cause\ndma_map_resource() to return DMA_MAPPING_ERROR.\n\nThis causes a WARNING on Raspberry Pi 4 during spi_bcm2835 probe because\nthe SPI FIFO register (0xfe204004) falls in the same sparsemem section\nas the end of RAM (0xf8000000-0xfbffffff), both in section 31\n(0xf8000000-0xffffffff).\n\nMove the sanity check from dma_map_resource() into debug_dma_map_phys()\nand replace the unreliable pfn_valid() with pfn_valid() &&\n!PageReserved(), which correctly identifies actual usable RAM without\nfalse positives for MMIO regions that happen to have struct pages.\n\nSince dma_map_resource() is dma_map_phys(DMA_ATTR_MMIO), the check\napplies equally to both APIs. Any non-reserved page represents kernel\nmemory to a sufficient degree that using DMA_ATTR_MMIO on it is almost\ncertainly wrong and risks breaking coherency on non-coherent platforms.\nZONE_DEVICE pages used for PCI P2P DMA (MEMORY_DEVICE_PCI_P2PDMA) have\nPageReserved set, so they will not trigger a false positive.\n\nThe check no longer blocks the mapping and uses err_printk() to\nintegrate with dma-debug filtering."
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