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

published 2026-07-19 3 mo ago modified 2026-08-17 2 mo ago also EUVD-2026-45834

cvss: 5.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 5%
public exploits: 0; none known

In the Linux kernel, the following vulnerability has been resolved:

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.

Patch / fix

fixed in 1 distros 2 links 3

Linux Linux 6.18.34, 7.0.11, 7.1

debian ubuntu

linux Debian 14 7.0.12-1

debian advisories DEBIAN-CVE-2026-64149

linux Ubuntu 26.04 LTS 7.0.0-28.28
linux-aws Ubuntu 26.04 LTS 7.0.0-1009.9
linux-gcp Ubuntu 26.04 LTS 7.0.0-1008.8
linux-gke Ubuntu 26.04 LTS 7.0.0-1003.4
linux-ibm Ubuntu 26.04 LTS 7.0.0-1010.10
linux-azure Ubuntu 26.04 LTS 7.0.0-1010.10
linux-raspi Ubuntu 26.04 LTS 7.0.0-1015.15
linux-riscv Ubuntu 26.04 LTS 7.0.0-28.28.1

ubuntu advisories UBUNTU-CVE-2026-64149

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-64149 updated 2026-11-07 cvss 5.5

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

Red Hat Enterprise Linux 10 kernel
affected: no fix available “Fix deferred”
Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.16% chance of exploitation in the next 30 days, higher than 5% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
NVD	3.1	5.5	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

Linux Linux

Classification

Technology feeds

Linux kernel rss critical rss

References

Sources

CVE List CVE-2026-64149
NVD CVE-2026-64149

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary