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FKIE_CVE-2026-93066

Vulnerability from fkie_nvd - Published: 2026-09-17 17:18 - Updated: 2026-09-17 17:18
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: x86/mm/pat: Take cpa_lock around large-page collapse Loading and unloading modules concurrently on several CPUs on a KASAN build, with a short delay injected at the CPA page-table lookup to widen the window, faults within minutes: BUG: KASAN: use-after-free in __change_page_attr+0x7cc/0x7e0 Write of size 8 at addr ffff888181139718 by task modprobe ... The buggy address belongs to the physical page: pfn:0x181139 ... page_type: f2(table) cpa_collapse_large_pages() rebuilds a leaf PMD from its 4K PTEs and frees the old PTE-table pages, while __change_page_attr() fetches a PTE pointer from a lockless lookup_address_in_pgd_attr() and writes it with set_pte_atomic() only later. When module text is served from a shared large ROX mapping the two run on the same PMD: CPU A (module load) CPU B (module finalize) ------------------- ----------------------- execmem_make_temp_rw set_memory_nx __change_page_attr split 2M -> 4K table P kpte = &P[i] (lockless) execmem_restore_rox set_memory_rox (CPA_COLLAPSE) cpa_collapse_large_pages rebuild leaf PMD flush_tlb_all pagetable_free(P) set_pte_atomic(kpte, ...) -> writes into freed P P is a page-table page (page_type: table), reused at once, so the write corrupts whatever got the page next: a bad-pte or bad-page splat, or a fatal fault once P has been turned into read-only text. The flush_tlb_all() before the free does not close this: its IPI only serializes against page-table walkers that run with interrupts off (e.g. GUP-fast); the walk in __change_page_attr() runs with interrupts on, so nothing stops it from holding a stale pointer into P. Serialize the collapse - the PMD rebuild, TLB flush and PTE-table free - under cpa_lock, the same lock __change_page_attr() now takes unconditionally since commit ("x86/mm/pat: stop gating cpa_lock on debug_pagealloc_enabled()"), so a concurrent walker can no longer hold a pointer into a table the collapse is about to free.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/1aac65f3e651334259ecb2a5f5ddb81c01f02599
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/591b6fac9df3f43522e8ff6eed8662f8b6f1a124
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/fb97d1d6c20692e15247fa5c8b894b2325e38aee
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/mm/pat/set_memory.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "591b6fac9df3f43522e8ff6eed8662f8b6f1a124",
              "status": "affected",
              "version": "41d88484c71cd4f659348da41b7b5b3dbd3be1f6",
              "versionType": "git"
            },
            {
              "lessThan": "fb97d1d6c20692e15247fa5c8b894b2325e38aee",
              "status": "affected",
              "version": "41d88484c71cd4f659348da41b7b5b3dbd3be1f6",
              "versionType": "git"
            },
            {
              "lessThan": "1aac65f3e651334259ecb2a5f5ddb81c01f02599",
              "status": "affected",
              "version": "41d88484c71cd4f659348da41b7b5b3dbd3be1f6",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/mm/pat/set_memory.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.15"
            },
            {
              "lessThan": "6.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.52",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86/mm/pat: Take cpa_lock around large-page collapse\n\nLoading and unloading modules concurrently on several CPUs on a KASAN\nbuild, with a short delay injected at the CPA page-table lookup to\nwiden the window, faults within minutes:\n\n  BUG: KASAN: use-after-free in __change_page_attr+0x7cc/0x7e0\n  Write of size 8 at addr ffff888181139718 by task modprobe\n  ...\n  The buggy address belongs to the physical page:\n   pfn:0x181139 ... page_type: f2(table)\n\ncpa_collapse_large_pages() rebuilds a leaf PMD from its 4K PTEs and\nfrees the old PTE-table pages, while __change_page_attr() fetches a\nPTE pointer from a lockless lookup_address_in_pgd_attr() and writes\nit with set_pte_atomic() only later. When module text is served from\na shared large ROX mapping the two run on the same PMD:\n\n  CPU A (module load)              CPU B (module finalize)\n  -------------------              -----------------------\n  execmem_make_temp_rw\n   set_memory_nx\n    __change_page_attr\n     split 2M -\u003e 4K table P\n     kpte = \u0026P[i]  (lockless)\n                                   execmem_restore_rox\n                                    set_memory_rox (CPA_COLLAPSE)\n                                     cpa_collapse_large_pages\n                                      rebuild leaf PMD\n                                      flush_tlb_all\n                                      pagetable_free(P)\n     set_pte_atomic(kpte, ...)\n       -\u003e writes into freed P\n\nP is a page-table page (page_type: table), reused at once, so the\nwrite corrupts whatever got the page next: a bad-pte or bad-page\nsplat, or a fatal fault once P has been turned into read-only text.\n\nThe flush_tlb_all() before the free does not close this: its IPI only\nserializes against page-table walkers that run with interrupts off\n(e.g. GUP-fast); the walk in __change_page_attr() runs with interrupts\non, so nothing stops it from holding a stale pointer into P.\n\nSerialize the collapse - the PMD rebuild, TLB flush and PTE-table\nfree - under cpa_lock, the same lock __change_page_attr() now takes\nunconditionally since commit (\"x86/mm/pat: stop gating cpa_lock on\ndebug_pagealloc_enabled()\"), so a concurrent walker can no longer\nhold a pointer into a table the collapse is about to free."
    }
  ],
  "id": "CVE-2026-93066",
  "lastModified": "2026-09-17T17:18:00.380",
  "metrics": {},
  "published": "2026-09-17T17:18:00.380",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/1aac65f3e651334259ecb2a5f5ddb81c01f02599"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/591b6fac9df3f43522e8ff6eed8662f8b6f1a124"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/fb97d1d6c20692e15247fa5c8b894b2325e38aee"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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