{"id":"CVE-2026-89758","summary":"mm/mempolicy: skip non-present PMDs when queueing folios","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/mempolicy: skip non-present PMDs when queueing folios\n\nPatch series \"mm: handle device-private PMDs in walk callbacks\", v3.\n\nSince commit 368076f52ebe (\"mm/huge_memory: add device-private THP support\nto PMD operations\") a PMD may hold a device-private swap entry whenever an\nHMM-based GPU driver migrates an anonymous THP folio to device memory via\nmigrate_vma_pages().\n\npmd_trans_huge_lock() succeeds for such PMDs (pmd_is_huge() returns true\nfor any non-present, non-none huge PMD), so several MM walk callbacks that\nused to assume present THP or migration entry are now reachable with a\ndevice-private PMD.  The results range from a VM_BUG_ON() firing on debug\nkernels, to an oops on a bogus vmemmap dereference, to silently isolating\nan unrelated live folio from LRU in the aliasing case.\n\n\nThis patch (of 3):\n\nqueue_folios_pmd() is called under pmd_trans_huge_lock(), whose\npmd_is_huge() check returns true for any non-present, non-none PMD\nsoftleaf.  Passing such a PMD to pmd_folio() treats the softleaf encoding\nas a hardware PFN and can return a bogus folio pointer.\n\nMirror queue_folios_pte_range(): handle non-present entries before looking\nup a folio.  Keep migration entries counted as failures, but skip other\nnon-present PMDs such as device-private entries.\n\nPotential trigger: an HMM-based GPU driver migrates an anonymous THP folio\nto device memory via migrate_vma_pages(), leaving a device-private PMD. \nUserspace then calls mbind(), migrate_pages() or set_mempolicy_home_node()\non that range.","modified":"2026-09-14T03:46:32.890846388Z","published":"2026-09-11T19:47:00.562Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89758.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/2858b4027f491e6fdb8ee2d8923798b619bf2791"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3d927093b2add7ced588a926c3dc5d7a83f18596"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89758.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89758"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"368076f52ebeecd33e10a9f80905d7508b6b6149"},{"fixed":"3d927093b2add7ced588a926c3dc5d7a83f18596"},{"fixed":"2858b4027f491e6fdb8ee2d8923798b619bf2791"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89758.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89758.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}