CVE-2026-97533 (GCVE-0-2026-97533)

Vulnerability from cvelistv5 – Published: 2026-09-25 10:21 – Updated: 2026-09-25 10:21
VLAI
Title
x86/mm/pat: Acquire init_mm read lock on attribute changes to avoid UAF
Summary
In the Linux kernel, the following vulnerability has been resolved: x86/mm/pat: Acquire init_mm read lock on attribute changes to avoid UAF A previous commit protected against races between ptdump and CPA collapse, however one still exists between attribute changes and collapse as reported by Denis V. Lunev (linked). When an attribute change arises, a lockless page table walker obtains a PTE entry, which is later written to via set_pte_atomic(): ... -> change_page_attr_set_clr() -> __change_page_attr_set_clr() -> __change_page_attr() -> _lookup_address_cpa() -> lookup_address_in_pgd_attr() -> [ lockless page table walker ] -> set_pte_atomic() There is nothing preventing a concurrent CPA collapse which can free the PTE that was retrieved here, resulting in a use-after-free. With the mmap write lock taken on init_mm over CPA collapse, resolve this race by acquiring an mmap read lock on init_mm over __change_page_attr_set_clr(). This locks across the whole operation over which the walk and the PTE entry write occurs, solving the race. It is safe to do this here, as no spinlocks are held upon entry to __change_page_attr_set_clr(). However, the lock must not be held over an allocation, as allocation can trigger reclaim and shrinkers may call into CPA recursively, making deadlocks possible (init_mm -> ... -> fs_reclaim -> init_mm). A page table is allocated when a huge page needs to be split: -> change_page_attr_set_clr() -> __change_page_attr_set_clr() -> __change_page_attr() -> split_large_page() [ pagetable_alloc() ] -> __split_large_page() Avoid deadlocks by dropping the mmap lock across pagetable_alloc() in split_large_page() and track whether this is needed by adding a new 'init_mm_read_locked' flag to struct cpa_data. This is safe as __split_large_page() (called with locks re-established) revalidates that the page table entry is the same as it was prior to the locks being dropped and __change_page_attr() repeats the entire page table walk whenever a split occurs, so concurrent split and collapse are accounted for. Concurrent ptdump is also safe as the lock is only dropped over page table allocation during which time the page table has not yet been modified. The CPA_COLLAPSE flag is only set by set_memory_rox(), which exclusively operates upon vmalloc ranges, and on x86 only within the module mapping space. This is important, because some callers directly invoke __change_page_attr_set_clr(), bypassing this lock. However, none of these operate within the module mapping space. * cpa_process_alias() - a recursive helper called by __change_page_attr_set_clr(). * __set_memory_enc_pgtable() - operates on the direct mapping and (via __vmbus_establish_gpadl()) the vmalloc mapping space. * __set_pages_[n]p() - called by set_direct_map_[invalid, default, valid]_noflush(), __kernel_map_pages() - operates on the direct map. * kernel_[un]map_pages_in_pgd() - operates on EFI ranges. This work is based upon Denis V. Lunev's excellent analysis of the bug with gratitude. [ dhansen: move to imperative voice in changelog ]
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 41d88484c71cd4f659348da41b7b5b3dbd3be1f6 , < e21a9ea81426a85fdb0cdcfcc99d5d9c16b402ab (git)
Affected: 41d88484c71cd4f659348da41b7b5b3dbd3be1f6 , < cc73b2043d106b467accd38e9b1fc09e0607c056 (git)
Affected: 41d88484c71cd4f659348da41b7b5b3dbd3be1f6 , < d5d8b8662e6e5a565b47a0388640e88402f23274 (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-rc4 , ≤ * (original_commit_for_fix)
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{
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      "affected": [
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/mm/pat/set_memory.c"
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              "status": "unaffected",
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              "versionType": "semver"
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              "version": "7.2.7",
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                  "vulnerable": true
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              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86/mm/pat: Acquire init_mm read lock on attribute changes to avoid UAF\n\nA previous commit protected against races between ptdump and CPA collapse,\nhowever one still exists between attribute changes and collapse as reported\nby Denis V. Lunev (linked).\n\nWhen an attribute change arises, a lockless page table walker obtains a PTE\nentry, which is later written to via set_pte_atomic():\n\n  ...\n  -\u003e change_page_attr_set_clr()\n  -\u003e __change_page_attr_set_clr()\n  -\u003e __change_page_attr()\n\t-\u003e _lookup_address_cpa()\n\t-\u003e lookup_address_in_pgd_attr()\n\t-\u003e [ lockless page table walker ]\n  -\u003e set_pte_atomic()\n\nThere is nothing preventing a concurrent CPA collapse which can free the\nPTE that was retrieved here, resulting in a use-after-free.\n\nWith the mmap write lock taken on init_mm over CPA collapse, resolve this\nrace by acquiring an mmap read lock on init_mm over\n__change_page_attr_set_clr().\n\nThis locks across the whole operation over which the walk and the PTE\nentry write occurs, solving the race.\n\nIt is safe to do this here, as no spinlocks are held upon entry to\n__change_page_attr_set_clr().\n\nHowever, the lock must not be held over an allocation, as allocation can\ntrigger reclaim and shrinkers may call into CPA recursively, making\ndeadlocks possible (init_mm -\u003e ... -\u003e fs_reclaim -\u003e init_mm).\n\nA page table is allocated when a huge page needs to be split:\n\n  -\u003e change_page_attr_set_clr()\n  -\u003e __change_page_attr_set_clr()\n  -\u003e __change_page_attr()\n  -\u003e split_large_page()\n  [ pagetable_alloc() ]\n  -\u003e __split_large_page()\n\nAvoid deadlocks by dropping the mmap lock across pagetable_alloc() in\nsplit_large_page() and track whether this is needed by adding a new\n\u0027init_mm_read_locked\u0027 flag to struct cpa_data.\n\nThis is safe as __split_large_page() (called with locks re-established)\nrevalidates that the page table entry is the same as it was prior to the\nlocks being dropped and __change_page_attr() repeats the entire page table\nwalk whenever a split occurs, so concurrent split and collapse are\naccounted for.\n\nConcurrent ptdump is also safe as the lock is only dropped over page table\nallocation during which time the page table has not yet been modified.\n\nThe CPA_COLLAPSE flag is only set by set_memory_rox(), which exclusively\noperates upon vmalloc ranges, and on x86 only within the module mapping\nspace.\n\nThis is important, because some callers directly invoke\n__change_page_attr_set_clr(), bypassing this lock. However, none of these\noperate within the module mapping space.\n\n  * cpa_process_alias() - a recursive helper called by\n    __change_page_attr_set_clr().\n  * __set_memory_enc_pgtable() - operates on the direct mapping and (via\n    __vmbus_establish_gpadl()) the vmalloc mapping space.\n  * __set_pages_[n]p() - called by set_direct_map_[invalid, default,\n    valid]_noflush(), __kernel_map_pages() - operates on the direct map.\n  * kernel_[un]map_pages_in_pgd() - operates on EFI ranges.\n\nThis work is based upon Denis V. Lunev\u0027s excellent analysis of the bug\nwith gratitude.\n\n[ dhansen: move to imperative voice in changelog ]"
        }
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        "dateUpdated": "2026-09-25T10:21:33.188Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/cc73b2043d106b467accd38e9b1fc09e0607c056"
        },
        {
          "url": "https://git.kernel.org/stable/c/d5d8b8662e6e5a565b47a0388640e88402f23274"
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      ],
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    "cveId": "CVE-2026-97533",
    "datePublished": "2026-09-25T10:21:33.188Z",
    "dateReserved": "2026-09-24T16:01:01.153Z",
    "dateUpdated": "2026-09-25T10:21:33.188Z",
    "state": "PUBLISHED"
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      "date": "2026-09-28",
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      "percentile": "0.10074"
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            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86/mm/pat: Acquire init_mm read lock on attribute changes to avoid UAF\n\nA previous commit protected against races between ptdump and CPA collapse,\nhowever one still exists between attribute changes and collapse as reported\nby Denis V. Lunev (linked).\n\nWhen an attribute change arises, a lockless page table walker obtains a PTE\nentry, which is later written to via set_pte_atomic():\n\n  ...\n  -\u003e change_page_attr_set_clr()\n  -\u003e __change_page_attr_set_clr()\n  -\u003e __change_page_attr()\n\t-\u003e _lookup_address_cpa()\n\t-\u003e lookup_address_in_pgd_attr()\n\t-\u003e [ lockless page table walker ]\n  -\u003e set_pte_atomic()\n\nThere is nothing preventing a concurrent CPA collapse which can free the\nPTE that was retrieved here, resulting in a use-after-free.\n\nWith the mmap write lock taken on init_mm over CPA collapse, resolve this\nrace by acquiring an mmap read lock on init_mm over\n__change_page_attr_set_clr().\n\nThis locks across the whole operation over which the walk and the PTE\nentry write occurs, solving the race.\n\nIt is safe to do this here, as no spinlocks are held upon entry to\n__change_page_attr_set_clr().\n\nHowever, the lock must not be held over an allocation, as allocation can\ntrigger reclaim and shrinkers may call into CPA recursively, making\ndeadlocks possible (init_mm -\u003e ... -\u003e fs_reclaim -\u003e init_mm).\n\nA page table is allocated when a huge page needs to be split:\n\n  -\u003e change_page_attr_set_clr()\n  -\u003e __change_page_attr_set_clr()\n  -\u003e __change_page_attr()\n  -\u003e split_large_page()\n  [ pagetable_alloc() ]\n  -\u003e __split_large_page()\n\nAvoid deadlocks by dropping the mmap lock across pagetable_alloc() in\nsplit_large_page() and track whether this is needed by adding a new\n\u0027init_mm_read_locked\u0027 flag to struct cpa_data.\n\nThis is safe as __split_large_page() (called with locks re-established)\nrevalidates that the page table entry is the same as it was prior to the\nlocks being dropped and __change_page_attr() repeats the entire page table\nwalk whenever a split occurs, so concurrent split and collapse are\naccounted for.\n\nConcurrent ptdump is also safe as the lock is only dropped over page table\nallocation during which time the page table has not yet been modified.\n\nThe CPA_COLLAPSE flag is only set by set_memory_rox(), which exclusively\noperates upon vmalloc ranges, and on x86 only within the module mapping\nspace.\n\nThis is important, because some callers directly invoke\n__change_page_attr_set_clr(), bypassing this lock. However, none of these\noperate within the module mapping space.\n\n  * cpa_process_alias() - a recursive helper called by\n    __change_page_attr_set_clr().\n  * __set_memory_enc_pgtable() - operates on the direct mapping and (via\n    __vmbus_establish_gpadl()) the vmalloc mapping space.\n  * __set_pages_[n]p() - called by set_direct_map_[invalid, default,\n    valid]_noflush(), __kernel_map_pages() - operates on the direct map.\n  * kernel_[un]map_pages_in_pgd() - operates on EFI ranges.\n\nThis work is based upon Denis V. Lunev\u0027s excellent analysis of the bug\nwith gratitude.\n\n[ dhansen: move to imperative voice in changelog ]"
          }
        ],
        "id": "CVE-2026-97533",
        "lastModified": "2026-09-25T11:17:03.520",
        "metrics": {},
        "published": "2026-09-25T11:17:03.520",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/cc73b2043d106b467accd38e9b1fc09e0607c056"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/d5d8b8662e6e5a565b47a0388640e88402f23274"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/e21a9ea81426a85fdb0cdcfcc99d5d9c16b402ab"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    }
  }
}



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