{
  "affected": [
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:14",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.0.13-1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "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.  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 (\"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.",
  "id": "DEBIAN-CVE-2026-53155",
  "modified": "2026-07-08T09:48:21.470724103Z",
  "published": "2026-06-25T09:16:32.877Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-53155"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "upstream": [
    "CVE-2026-53155"
  ]
}