CVE-2026-97943 (GCVE-0-2026-97943)

Vulnerability from cvelistv5 – Published: 2026-09-25 10:22 – Updated: 2026-10-19 09:11
VLAI
Title
x86/mm/pat: Acquire init_mm write lock on collapse to avoid UAF
Summary
In the Linux kernel, the following vulnerability has been resolved: x86/mm/pat: Acquire init_mm write lock on collapse to avoid UAF x86 implements page attribute modification using its Change Page Attributes (CPA) mechanism. This tracks properties of ranges such as cache mode through x86 page attributes, and as part of that logic manipulates kernel page tables. Since commit: 41d88484c71c ("x86/mm/pat: restore large ROX pages after fragmentation") ranges of kernel page table entries can be collapsed into huge page table entries as part of this logic. As part of this collapse, it frees the page tables which the collapsed entries previously pointed to, and it does so without any relevant locks being held to preclude concurrent kernel page table walkers. The only way this code can be reached is if CPA_COLLAPSE is specified, and this is only set in set_memory_rox() via: set_memory_rox() -> change_page_attr_set_clr() -> cpa_flush() -> cpa_collapse_large_pages() Notable users of this are execmem and BPF when manipulating executable mappings. However, this is problematic for ptdump as it walks ranges it does not own and thus runs the risk of a use-after-free on page tables freed underneath it. In addition, concurrent CPA collapse operations are possible which can also cause races. Resolve the issue by acquiring the mmap write lock on init_mm across the whole operation. It is safe to acquire a sleeping lock as all the callers invoke set_memory_rox() from process context and in any case, change_page_attr_set_clr() calls vm_unmap_alias() which ultimately takes a mutex, disallowing atomic context here.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6641 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 41d88484c71cd4f659348da41b7b5b3dbd3be1f6 , < 35820cf8dd521f5a651e221483015b0586794516 (git)
Affected: 41d88484c71cd4f659348da41b7b5b3dbd3be1f6 , < 93b98882198b15bd482da1fe8e84b05c7c3b3d83 (git)
Affected: 41d88484c71cd4f659348da41b7b5b3dbd3be1f6 , < a1c7570cedd03372812a5b693732880867babbca (git)
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Linux Linux Affected: 6.15
Unaffected: 0 , < 6.15 (semver)
Unaffected: 6.18.53 , ≤ 6.18.* (semver)
Unaffected: 7.2.7 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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{
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86/mm/pat: Acquire init_mm write lock on collapse to avoid UAF\n\nx86 implements page attribute modification using its Change Page\nAttributes (CPA) mechanism.\n\nThis tracks properties of ranges such as cache mode through x86 page\nattributes, and as part of that logic manipulates kernel page tables.\n\nSince commit:\n\n  41d88484c71c (\"x86/mm/pat: restore large ROX pages after fragmentation\")\n\nranges of kernel page table entries can be collapsed into\nhuge page table entries as part of this logic.\n\nAs part of this collapse, it frees the page tables which the collapsed\nentries previously pointed to, and it does so without any relevant locks\nbeing held to preclude concurrent kernel page table walkers.\n\nThe only way this code can be reached is if CPA_COLLAPSE is specified, and\nthis is only set in set_memory_rox() via:\n\nset_memory_rox()\n-\u003e change_page_attr_set_clr()\n-\u003e cpa_flush()\n-\u003e cpa_collapse_large_pages()\n\nNotable users of this are execmem and BPF when manipulating executable\nmappings.\n\nHowever, this is problematic for ptdump as it walks ranges it does not own\nand thus runs the risk of a use-after-free on page tables freed underneath\nit.\n\nIn addition, concurrent CPA collapse operations are possible which can also\ncause races.\n\nResolve the issue by acquiring the mmap write lock on init_mm across the\nwhole operation.\n\nIt is safe to acquire a sleeping lock as all the callers invoke\nset_memory_rox() from process context and in any case,\nchange_page_attr_set_clr() calls vm_unmap_alias() which ultimately takes a\nmutex, disallowing atomic context here."
        }
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        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/a1c7570cedd03372812a5b693732880867babbca"
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    "cveId": "CVE-2026-97943",
    "datePublished": "2026-09-25T10:22:54.787Z",
    "dateReserved": "2026-09-25T10:18:58.204Z",
    "dateUpdated": "2026-10-19T09:11:09.731Z",
    "state": "PUBLISHED"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86/mm/pat: Acquire init_mm write lock on collapse to avoid UAF\n\nx86 implements page attribute modification using its Change Page\nAttributes (CPA) mechanism.\n\nThis tracks properties of ranges such as cache mode through x86 page\nattributes, and as part of that logic manipulates kernel page tables.\n\nSince commit:\n\n  41d88484c71c (\"x86/mm/pat: restore large ROX pages after fragmentation\")\n\nranges of kernel page table entries can be collapsed into\nhuge page table entries as part of this logic.\n\nAs part of this collapse, it frees the page tables which the collapsed\nentries previously pointed to, and it does so without any relevant locks\nbeing held to preclude concurrent kernel page table walkers.\n\nThe only way this code can be reached is if CPA_COLLAPSE is specified, and\nthis is only set in set_memory_rox() via:\n\nset_memory_rox()\n-\u003e change_page_attr_set_clr()\n-\u003e cpa_flush()\n-\u003e cpa_collapse_large_pages()\n\nNotable users of this are execmem and BPF when manipulating executable\nmappings.\n\nHowever, this is problematic for ptdump as it walks ranges it does not own\nand thus runs the risk of a use-after-free on page tables freed underneath\nit.\n\nIn addition, concurrent CPA collapse operations are possible which can also\ncause races.\n\nResolve the issue by acquiring the mmap write lock on init_mm across the\nwhole operation.\n\nIt is safe to acquire a sleeping lock as all the callers invoke\nset_memory_rox() from process context and in any case,\nchange_page_attr_set_clr() calls vm_unmap_alias() which ultimately takes a\nmutex, disallowing atomic context here."
          }
        ],
        "id": "CVE-2026-97943",
        "lastModified": "2026-10-19T10:17:45.520",
        "metrics": {},
        "published": "2026-09-25T11:17:21.750",
        "references": [
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      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97943.json",
      "version": "3"
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}



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