« Volver al listado

CVE-2026-53155

Estado: AnalizadaMedia (5.5)—

In the Linux kernel, the following vulnerability has been resolved:

mm/huge_memory: use correct flags for device private PMD entry

Commit 65edfda6f3f2 ("mm/rmap: extend rmap and migration support device-private entries") updated set_pmd_migration_entry() to use pmdp_huge_get_and_clear() in the softleaf case, but made no further adjustments to the function itself.

Therefore this function continues to incorrectly use pmd_write(), pmd_soft_dirty() and pmd_uffd_wp() to determine whether the installed migration entry should be marked writable, softdirty or uffd-wp respectively.

Whilst all are incorrect, the most problematic of these is pmd_write(), as this can lead to corrupted rmap state.

Leer descripción completaMostrar menos

On x86-64 _PAGE_SWP_SOFT_DIRTY is aliased to _PAGE_RW. So calling pmd_write() on a softleaf will return the softdirty state encoded in the entry, assuming CONFIG_MEM_SOFT_DIRTY was enabled.

This was observed when running the hmm.hmm_device_private.anon_write_child selftest:

VM_WARN_ON_FOLIO(folio_test_large(folio) && folio_entire_mapcount(folio) > 1 && PageAnonExclusive(cur_page), folio)

This patch fixes the issue by correctly referencing the softleaf entry fields for writable, softdirty and uffd-wp in set_pmd_migration_entry().

It also only updates A/D flags if the entry is present as these are otherwise not meaningful for a softleaf entry.

This patch also flips the if (!present) { ... } else { ... } logic in set_pmd_migration_entry() so it is easier to understand, and adds some comments to make things clearer.

I was able to bisect this to commit 775465fd26a3 ("lib/test_hmm: add zone device private THP test infrastructure") which first exposes this bug as it was the commit that permitted test_hmm to generate the test.

However commit 65edfda6f3f2 ("mm/rmap: extend rmap and migration support device-private entries") is the commit that actually enabled this behaviour.

Detalles técnicos trazas, registros y código del informe original
1. The test faults in a range then migrates it such that a device-private
   THP range is established.

2. The parent then migrates it to a device-private writable PMD entry whose
   folio is entirely AnonExclusive with entire_mapcount=1, softdirty set
   (accidentally correct write state).

3. The parent forks and the PMD entries are set to device-private read only
   entries, entire_mapcount=2, softdirty still set.

4. [BUG] The child writes to the range then migrates to RAM - intending to
   install non-writable migration entries - but replacing parent and child
   PMD mappings with WRITABLE entries due to misinterpreting the softdirty
   bit.

5. In remove_migration_pmd(), if !softleaf_is_migration_read(entry) we
   set the RMAP_EXCLUSIVE flag when calling folio_add_anon_rmap_pmd() for
   both parent and child, which are therefore AnonExclusive.

6. [SPLAT] Child sets migrated folio entire_mapcount=1, parent sets
   entire_mapcount=2 and we end up with an AnonExclusive folio with
   entire_mapcount=2! Assert fires in __folio_add_anon_rmap():

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

Mostrar
{
  "id": "CVE-2026-53155",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.5,
          "attackVector": "LOCAL",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 1.8
      }
    ]
  },
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "65edfda6f3f2e58f757485a056e4f1775a1404a8",
              "lessThan": "d7251c8d3f7cea76543abac6cf4ed15582c10846",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "65edfda6f3f2e58f757485a056e4f1775a1404a8",
              "lessThan": "43e7f189769c512c843184a8a5892ac779a6bd90",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "mm/huge_memory.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.19"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "6.19",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "7.0.13",
              "versionType": "semver",
              "lessThanOrEqual": "7.0.*"
            },
            {
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "mm/huge_memory.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-06-25T09:16:32.877",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/43e7f189769c512c843184a8a5892ac779a6bd90",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/d7251c8d3f7cea76543abac6cf4ed15582c10846",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/huge_memory: use correct flags for device private PMD entry\n\nCommit 65edfda6f3f2 (\"mm/rmap: extend rmap and migration support\ndevice-private entries\") updated set_pmd_migration_entry() to use\npmdp_huge_get_and_clear() in the softleaf case, but made no further\nadjustments to the function itself.\n\nTherefore this function continues to incorrectly use pmd_write(),\npmd_soft_dirty() and pmd_uffd_wp() to determine whether the installed\nmigration entry should be marked writable, softdirty or uffd-wp\nrespectively.\n\nWhilst all are incorrect, the most problematic of these is pmd_write(), as\nthis can lead to corrupted rmap state.\n\nOn x86-64 _PAGE_SWP_SOFT_DIRTY is aliased to _PAGE_RW.  So calling\npmd_write() on a softleaf will return the softdirty state encoded in the\nentry, assuming CONFIG_MEM_SOFT_DIRTY was enabled.\n\nThis was observed when running the hmm.hmm_device_private.anon_write_child\nselftest:\n\n1. The test faults in a range then migrates it such that a device-private\n   THP range is established.\n\n2. The parent then migrates it to a device-private writable PMD entry whose\n   folio is entirely AnonExclusive with entire_mapcount=1, softdirty set\n   (accidentally correct write state).\n\n3. The parent forks and the PMD entries are set to device-private read only\n   entries, entire_mapcount=2, softdirty still set.\n\n4. [BUG] The child writes to the range then migrates to RAM - intending to\n   install non-writable migration entries - but replacing parent and child\n   PMD mappings with WRITABLE entries due to misinterpreting the softdirty\n   bit.\n\n5. In remove_migration_pmd(), if !softleaf_is_migration_read(entry) we\n   set the RMAP_EXCLUSIVE flag when calling folio_add_anon_rmap_pmd() for\n   both parent and child, which are therefore AnonExclusive.\n\n6. [SPLAT] Child sets migrated folio entire_mapcount=1, parent sets\n   entire_mapcount=2 and we end up with an AnonExclusive folio with\n   entire_mapcount=2! Assert fires in __folio_add_anon_rmap():\n\n\t\tVM_WARN_ON_FOLIO(folio_test_large(folio) &&\n\t\t\t\t folio_entire_mapcount(folio) > 1 &&\n\t\t\t\t PageAnonExclusive(cur_page), folio)\n\nThis patch fixes the issue by correctly referencing the softleaf entry\nfields for writable, softdirty and uffd-wp in set_pmd_migration_entry().\n\nIt also only updates A/D flags if the entry is present as these are\notherwise not meaningful for a softleaf entry.\n\nThis patch also flips the if (!present) { ...  } else { ...  } logic in\nset_pmd_migration_entry() so it is easier to understand, and adds some\ncomments to make things clearer.\n\nI was able to bisect this to commit 775465fd26a3 (\"lib/test_hmm: add zone\ndevice private THP test infrastructure\") which first exposes this bug as\nit was the commit that permitted test_hmm to generate the test.\n\nHowever commit 65edfda6f3f2 (\"mm/rmap: extend rmap and migration support\ndevice-private entries\") is the commit that actually enabled this\nbehaviour."
    }
  ],
  "lastModified": "2026-07-07T20:10:10.803",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "6A64BF9F-3BCA-42FD-98CB-8F03474D2B1E",
              "versionEndExcluding": "7.0.13",
              "versionStartIncluding": "6.19"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "B1EF7059-E670-45F4-B422-54C40FA86390"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "0D38F0BF-A728-4133-A358-D44A2F7EE6D6"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc3:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "EC732D08-5F7B-46D9-B154-E60C7F4F0A97"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc4:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "E5910A9D-F60A-409A-B486-FE66BFEBA9B9"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc5:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "81DFF19E-9CF8-49C6-8C36-1E4038622933"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc6:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "B0E8FC71-3952-444C-83E9-718DBBBEC615"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc7:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "1039E95A-8CC3-4C88-8FF9-5C08EEB861C9"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}