{
  "cveId": "CVE-2026-53155",
  "url": "https://patchblox.com/security/cve/CVE-2026-53155",
  "summary": "CVE-2026-53155 is fixed in linux on 1 platform by DEBIAN-CVE-2026-53155 (version 7.0.13-1), released June 28, 2026. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "linux: In the Linux kernel, the following vulnerability has been resolved:  mm/huge_memory: use correct flags for device pri...",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  mm/huge_memory: use correct flags for device private PMD entry  Commit 65edfda6f3f2 (\u0022mm/rmap: extend rmap and migration support device-private entries\u0022) 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.  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:  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():  \t\tVM_WARN_ON_FOLIO(folio_test_large(folio) \u0026\u0026 \t\t\t\t folio_entire_mapcount(folio) \u003E 1 \u0026\u0026 \t\t\t\t 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 (\u0022lib/test_hmm: add zone device private THP test infrastructure\u0022) which first exposes this bug as it was the commit that permitted test_hmm to generate the test.  However commit 65edfda6f3f2 (\u0022mm/rmap: extend rmap and migration support device-private entries\u0022) is the commit that actually enabled this behaviour.",
  "published": "2026-06-25T09:16:32Z",
  "severity": "medium",
  "cvss": 5.5,
  "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
  "epss": 0.00143,
  "epssPercentile": 0.0366,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.0.13-1",
      "fix": "DEBIAN-CVE-2026-53155",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-53155",
      "released": "2026-06-28T17:47:07Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T06:59:42Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}