FKIE_CVE-2026-74599

Vulnerability from fkie_nvd - Published: 2026-08-22 16:16 - Updated: 2026-08-23 13:16
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: mm/ptdump: always stabilise against page table freeing using init_mm Previous commits have established the invariant that kernel page table freeing is performed while an mmap read lock on init_mm is held, which fixes races between ptdump and kernel page table freeing over init_mm. However, x86 and arm64 can perform a ptdump over an mm other than init_mm via ptdump_walk_pgd() and since kernel memory ranges are shared across non-kernel mm's, this means that the race still exists for these cases. Fix this by acquiring a nested mmap write lock for init_mm in ptdump_walk_pgd(). This is safe as we take this after mmap write locking the mm, and nothing acquires the init_mm lock first before locking an arbitrary mm, so no deadlock is possible. Also update walk_page_range_debug() to assert that init_mm is write locked, add a comment explaining why and remove some redundant code, and eliminate the unnecessary and confusing invocation of walk_kernel_page_table_range(). We can safely remove the non-NULL check for walk.mm, as the mmap lock asserts would NULL pointer deref if it was (and of course no callers do this). The first point at which ptdump can race kernel page table freeing is commit b6bdb7517c3d ("mm/vmalloc: add interfaces to free unmapped page table"), so we target this in the Fixes tag.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/27c32e5538344b13c1505a08861e04620c125d47
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3c0391b9a774cc0854f3152e484a9d4835b12b40
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/4adc4c9a9a43d61fe476dfe10811f3df2e7e4106
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/76df4edf7d61ecb711bc517ff4c20a5e85c4e9f7
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7f740664aec1f832953c2e6d9b8920cd6c8bcc0c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b9c6d048bdfaae78d7d921b454f7de7baefaa2f0
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/cbd9583bb6f70733d0022a66d3546a15c76ae744
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "mm/pagewalk.c",
            "mm/ptdump.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "3c0391b9a774cc0854f3152e484a9d4835b12b40",
              "status": "affected",
              "version": "b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e",
              "versionType": "git"
            },
            {
              "lessThan": "cbd9583bb6f70733d0022a66d3546a15c76ae744",
              "status": "affected",
              "version": "b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e",
              "versionType": "git"
            },
            {
              "lessThan": "76df4edf7d61ecb711bc517ff4c20a5e85c4e9f7",
              "status": "affected",
              "version": "b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e",
              "versionType": "git"
            },
            {
              "lessThan": "b9c6d048bdfaae78d7d921b454f7de7baefaa2f0",
              "status": "affected",
              "version": "b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e",
              "versionType": "git"
            },
            {
              "lessThan": "7f740664aec1f832953c2e6d9b8920cd6c8bcc0c",
              "status": "affected",
              "version": "b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e",
              "versionType": "git"
            },
            {
              "lessThan": "4adc4c9a9a43d61fe476dfe10811f3df2e7e4106",
              "status": "affected",
              "version": "b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e",
              "versionType": "git"
            },
            {
              "lessThan": "27c32e5538344b13c1505a08861e04620c125d47",
              "status": "affected",
              "version": "b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "31895cfd79564111cdd5a9f48c5d491ae26a238e",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "9c7f7bdb1932f8c1e5f80d32c717184701afe701",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "acdb4981644c8e31ccee294bdefff475c0cf587b",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "0454e2fad9306961540ee7e84da47a8e345b7d22",
              "versionType": "git"
            },
            {
              "lessThan": "4.5",
              "status": "affected",
              "version": "4.4.125",
              "versionType": "semver"
            },
            {
              "lessThan": "4.10",
              "status": "affected",
              "version": "4.9.91",
              "versionType": "semver"
            },
            {
              "lessThan": "4.15",
              "status": "affected",
              "version": "4.14.31",
              "versionType": "semver"
            },
            {
              "lessThan": "4.16",
              "status": "affected",
              "version": "4.15.14",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "mm/pagewalk.c",
            "mm/ptdump.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.16"
            },
            {
              "lessThan": "4.16",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.266",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.217",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.153",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.105",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.45",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "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\nmm/ptdump: always stabilise against page table freeing using init_mm\n\nPrevious commits have established the invariant that kernel page table\nfreeing is performed while an mmap read lock on init_mm is held, which\nfixes races between ptdump and kernel page table freeing over init_mm.\n\nHowever, x86 and arm64 can perform a ptdump over an mm other than init_mm\nvia ptdump_walk_pgd() and since kernel memory ranges are shared across\nnon-kernel mm\u0027s, this means that the race still exists for these cases.\n\nFix this by acquiring a nested mmap write lock for init_mm in\nptdump_walk_pgd().\n\nThis is safe as we take this after mmap write locking the mm, and nothing\nacquires the init_mm lock first before locking an arbitrary mm, so no\ndeadlock is possible.\n\nAlso update walk_page_range_debug() to assert that init_mm is write\nlocked, add a comment explaining why and remove some redundant code, and\neliminate the unnecessary and confusing invocation of\nwalk_kernel_page_table_range().\n\nWe can safely remove the non-NULL check for walk.mm, as the mmap lock\nasserts would NULL pointer deref if it was (and of course no callers do\nthis).\n\nThe first point at which ptdump can race kernel page table freeing is\ncommit b6bdb7517c3d (\"mm/vmalloc: add interfaces to free unmapped page\ntable\"), so we target this in the Fixes tag."
    }
  ],
  "id": "CVE-2026-74599",
  "lastModified": "2026-08-23T13:16:46.343",
  "metrics": {},
  "published": "2026-08-22T16:16:32.303",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/27c32e5538344b13c1505a08861e04620c125d47"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3c0391b9a774cc0854f3152e484a9d4835b12b40"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4adc4c9a9a43d61fe476dfe10811f3df2e7e4106"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/76df4edf7d61ecb711bc517ff4c20a5e85c4e9f7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7f740664aec1f832953c2e6d9b8920cd6c8bcc0c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b9c6d048bdfaae78d7d921b454f7de7baefaa2f0"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/cbd9583bb6f70733d0022a66d3546a15c76ae744"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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