Bug 2525454 (CVE-2026-80685)

Summary: CVE-2026-80685 kernel: mm/util: don't read __page_2 for order-1 folios in snapshot_page()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: low    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's memory management subsystem. The `snapshot_page()` function attempts to read memory that may not exist when handling certain memory structures (order-1 folios) during specific memory operations, such as dynamic logical partitioning (DLPAR) memory removal. This out-of-bounds read can lead to a kernel fault (oops), resulting in a system crash and a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-08-28 07:45:47 UTC 
In the Linux kernel, the following vulnerability has been resolved:

mm/util: don't read __page_2 for order-1 folios in snapshot_page()

snapshot_page() currently reads __page_2 after checking nr_pages > 1, but
it should only do so when nr_pages > 2.

If an order-1 folio is allocated at the end of a vmemmap section,
__page_2 will not exist and reading it will cause a fault.

During DLPAR memory remove on a 22 TB ppc64le LPAR, snapshot_page() oopsed
on the page isolation path while reading an order-1 folio's __page_2 from
an adjacent absent section (unmapped vmemmap).

Fix this to avoid reading memmap that doesn't exist (e.g., a vmemmap
hole).
Comment 1 gkamathe 2026-09-01 11:44:24 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026082802-CVE-2026-80685-a81f@gregkh/T