CVE-2025-21696 (GCVE-0-2025-21696)
Vulnerability from cvelistv5
Published
2025-02-12 13:27
Modified
2025-05-04 07:19
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: mm: clear uffd-wp PTE/PMD state on mremap() When mremap()ing a memory region previously registered with userfaultfd as write-protected but without UFFD_FEATURE_EVENT_REMAP, an inconsistency in flag clearing leads to a mismatch between the vma flags (which have uffd-wp cleared) and the pte/pmd flags (which do not have uffd-wp cleared). This mismatch causes a subsequent mprotect(PROT_WRITE) to trigger a warning in page_table_check_pte_flags() due to setting the pte to writable while uffd-wp is still set. Fix this by always explicitly clearing the uffd-wp pte/pmd flags on any such mremap() so that the values are consistent with the existing clearing of VM_UFFD_WP. Be careful to clear the logical flag regardless of its physical form; a PTE bit, a swap PTE bit, or a PTE marker. Cover PTE, huge PMD and hugetlb paths.
References
Impacted products
Vendor Product Version
Linux Linux Version: 63b2d4174c4ad1f40b48d7138e71bcb564c1fe03
Version: 63b2d4174c4ad1f40b48d7138e71bcb564c1fe03
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/linux/userfaultfd_k.h",
            "mm/huge_memory.c",
            "mm/hugetlb.c",
            "mm/mremap.c"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm: clear uffd-wp PTE/PMD state on mremap()\n\nWhen mremap()ing a memory region previously registered with userfaultfd as\nwrite-protected but without UFFD_FEATURE_EVENT_REMAP, an inconsistency in\nflag clearing leads to a mismatch between the vma flags (which have\nuffd-wp cleared) and the pte/pmd flags (which do not have uffd-wp\ncleared).  This mismatch causes a subsequent mprotect(PROT_WRITE) to\ntrigger a warning in page_table_check_pte_flags() due to setting the pte\nto writable while uffd-wp is still set.\n\nFix this by always explicitly clearing the uffd-wp pte/pmd flags on any\nsuch mremap() so that the values are consistent with the existing clearing\nof VM_UFFD_WP.  Be careful to clear the logical flag regardless of its\nphysical form; a PTE bit, a swap PTE bit, or a PTE marker.  Cover PTE,\nhuge PMD and hugetlb paths."
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      "providerMetadata": {
        "dateUpdated": "2025-05-04T07:19:13.697Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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      "title": "mm: clear uffd-wp PTE/PMD state on mremap()",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-21696",
    "datePublished": "2025-02-12T13:27:54.905Z",
    "dateReserved": "2024-12-29T08:45:45.743Z",
    "dateUpdated": "2025-05-04T07:19:13.697Z",
    "state": "PUBLISHED"
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  }
}


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