{"id":"CVE-2026-80893","title":"mm/hugetlb: fix swap entry corruption when clearing uffd-wp at fork()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/hugetlb: fix swap entry corruption when clearing uffd-wp at fork()\n\ncopy_hugetlb_page_range() clears the uffd-wp bit of migration and hwpoison\nentries with huge_pte_…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= bc70fbf269fdff410b0b6d75c3770b9f59117b90 < f1b1311c0352873137768bac5a126e491271a747","Linux >= bc70fbf269fdff410b0b6d75c3770b9f59117b90 < 69cb5825d9988c7944bc9f1dc08cb233655405a7","Linux >= bc70fbf269fdff410b0b6d75c3770b9f59117b90 < 8b0de7005b148738d79d6c45594d566489948a68","Linux >= bc70fbf269fdff410b0b6d75c3770b9f59117b90 < 2b9a07002c2f296aa6a9c591213933d3492e3089","Linux >= bc70fbf269fdff410b0b6d75c3770b9f59117b90 < 2fa11c60c9c06bafc19cf4d9efdaa36a38079e87","Linux >= bc70fbf269fdff410b0b6d75c3770b9f59117b90 < 83abe2fd5b3aeb3123b5408a5a91709c5538fb23","Linux 5.19"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-06T17:04:44.937840Z"},"published":"2026-09-04","updated":"2026-11-06","sourceUpdated":"2026-11-06T17:05:56.363Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-80893","references":[{"url":"https://git.kernel.org/stable/c/f1b1311c0352873137768bac5a126e491271a747"},{"url":"https://git.kernel.org/stable/c/69cb5825d9988c7944bc9f1dc08cb233655405a7"},{"url":"https://git.kernel.org/stable/c/8b0de7005b148738d79d6c45594d566489948a68"},{"url":"https://git.kernel.org/stable/c/2b9a07002c2f296aa6a9c591213933d3492e3089"},{"url":"https://git.kernel.org/stable/c/2fa11c60c9c06bafc19cf4d9efdaa36a38079e87"},{"url":"https://git.kernel.org/stable/c/83abe2fd5b3aeb3123b5408a5a91709c5538fb23"}],"tags":["cve.org"],"epss":0.00173,"epssPercentile":0.06691,"ingestedAt":"2026-11-06T18:00:12.526Z","slug":"CVE-2026-80893","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nmm/hugetlb: fix swap entry corruption when clearing uffd-wp at fork()\n\ncopy_hugetlb_page_range() clears the uffd-wp bit of migration and hwpoison\nentries with huge_pte_clear_uffd_wp(), which operates on the present-PTE\nbit position.  Swap entries keep the uffd-wp state elsewhere -- the\nmigration branch reads and sets it with pte_swp_uffd_wp() and\npte_swp_mkuffd_wp() -- and the present-PTE position falls into the swap\npayload.  On x86-64 it lands in the inverted swap offset, where a\nnaturally-aligned hugetlb PFN always has the affected bit set, so the\nclear advances the encoded PFN by two pages.\n\nNo userfaultfd needs to be involved: the clear is guarded only by the\nchild VMA not being uffd-wp registered, so a plain fork() with an\nin-flight hugetlb migration entry (or a poisoned hugetlb page) corrupts\nthe entry copied into the child.  Instrumenting the clear and forking\nafter MADV_HWPOISON on a 2MB anon hugetlb page shows:\n\n  offset before=120e00\n  offset after =120e02\n\nThe fallout is mostly latent: rmap walks match migration entries by folio\nrange and remove_migration_pte() rebuilds the PTE from the folio, so a\nwithin-folio PFN skew heals once migration completes.  But any path that\nre-encodes the corrupted offset -- e.g.  hugetlb_change_protection()\nrewriting a writable migration entry via\nmake_readable_migration_entry(swp_offset(entry)) -- propagates it.\n\nMigration entries legitimately carry uffd-wp, so clear it with\npte_swp_clear_uffd_wp(), matching copy_nonpresent_pte() and\nmove_huge_pte().\n\nA hwpoison entry, on the other hand, never carries the uffd-wp bit: it is\ninstalled fresh by make_hwpoison_entry() (try_to_unmap_one() does not\npreserve uffd-wp on the hwpoison path) and hugetlb_change_protection()\nleaves hwpoison entries untouched.  There was nothing to clear there, only\nthe corruption, so drop the clear entirely.\n\n## Affected\n\n- `Linux >= bc70fbf269fdff410b0b6d75c3770b9f59117b90 < f1b1311c0352873137768bac5a126e491271a747`\n- `Linux >= bc70fbf269fdff410b0b6d75c3770b9f59117b90 < 69cb5825d9988c7944bc9f1dc08cb233655405a7`\n- `Linux >= bc70fbf269fdff410b0b6d75c3770b9f59117b90 < 8b0de7005b148738d79d6c45594d566489948a68`\n- `Linux >= bc70fbf269fdff410b0b6d75c3770b9f59117b90 < 2b9a07002c2f296aa6a9c591213933d3492e3089`\n- `Linux >= bc70fbf269fdff410b0b6d75c3770b9f59117b90 < 2fa11c60c9c06bafc19cf4d9efdaa36a38079e87`\n- `Linux >= bc70fbf269fdff410b0b6d75c3770b9f59117b90 < 83abe2fd5b3aeb3123b5408a5a91709c5538fb23`\n- `Linux 5.19`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}