CVE-2026-89961

/// Technical description

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

powerpc/mm: fix wrong addr_pfn tracking in compound vmemmap population

vmemmap_populate_compound_pages() uses addr_pfn to determine the PFN

offset within a compound page and to decide whether the current vmemmap

slot should be populated as a head page mapping or should reuse a tail

page mapping.

However, addr_pfn is advanced manually in parallel with addr. The loop

itself progresses in vmemmap address space, so each PAGE_SIZE step in addr

covers PAGE_SIZE / sizeof(struct page) struct page slots. Since addr_pfn

is compared against nr_pages in data-PFN units, it should advance by the

same number of PFNs. The existing manual increments do not match that and

therefore do not reliably track the PFN corresponding to the current addr.

As a result, pfn_offset can be computed from the wrong PFN and the code

can make the head/tail decision for the wrong compound-page position.

Fix this by deriving addr_pfn directly from

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References