Linux Kernel up to 7.2.3 mempolicy mm/mempolicy.c queue_folios_pmd memory corruption

Summaryinfo

A vulnerability described as very critical has been identified in Linux Kernel up to 7.2.3. The impacted element is the function queue_folios_pmd of the file mm/mempolicy.c of the component mempolicy. Such manipulation leads to memory corruption. This vulnerability is documented as CVE-2026-89758. The attack needs to be performed locally. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.3. It has been rated as very critical. Affected by this issue is the function queue_folios_pmd of the file mm/mempolicy.c of the component mempolicy. The manipulation with an unknown input leads to a memory corruption vulnerability. Using CWE to declare the problem leads to CWE-119. The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: mm/mempolicy: skip non-present PMDs when queueing folios Patch series "mm: handle device-private PMDs in walk callbacks", v3. Since commit 368076f52ebe ("mm/huge_memory: add device-private THP support to PMD operations") a PMD may hold a device-private swap entry whenever an HMM-based GPU driver migrates an anonymous THP folio to device memory via migrate_vma_pages(). pmd_trans_huge_lock() succeeds for such PMDs (pmd_is_huge() returns true for any non-present, non-none huge PMD), so several MM walk callbacks that used to assume present THP or migration entry are now reachable with a device-private PMD. The results range from a VM_BUG_ON() firing on debug kernels, to an oops on a bogus vmemmap dereference, to silently isolating an unrelated live folio from LRU in the aliasing case. This patch (of 3): queue_folios_pmd() is called under pmd_trans_huge_lock(), whose pmd_is_huge() check returns true for any non-present, non-none PMD softleaf. Passing such a PMD to pmd_folio() treats the softleaf encoding as a hardware PFN and can return a bogus folio pointer. Mirror queue_folios_pte_range(): handle non-present entries before looking up a folio. Keep migration entries counted as failures, but skip other non-present PMDs such as device-private entries. Potential trigger: an HMM-based GPU driver migrates an anonymous THP folio to device memory via migrate_vma_pages(), leaving a device-private PMD. Userspace then calls mbind(), migrate_pages() or set_mempolicy_home_node() on that range.

The advisory is shared for download at git.kernel.org. This vulnerability is handled as CVE-2026-89758 since 09/11/2026. The exploitation is known to be easy. The attack needs to be approached locally. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/11/2026).

Upgrading to version 7.2.4 or 7.3-rc1 eliminates this vulnerability. Applying the patch 3d927093b2add7ced588a926c3dc5d7a83f18596/2858b4027f491e6fdb8ee2d8923798b619bf2791 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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