Intel

CVE-2026-53155

Linux kernel (GCP) vulnerabilities

mediumEPSS 0.1%

Description

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():

     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.

Source: UBUNTU_USNUBUNTU_USNUBUNTU_USNBSIBSI_CSAFCVELISTV5NVDCVEORG

Metrics

Severity
medium
Priority score
231.31
KEV status
—
Exploit maturity
no public PoC known
XIEM Effective CVSS
5.5
Source: nvd-v3
CVSS v3
5.5
CVSS v4
—
EPSS percentile
3.9 %
Low — this CVE sits in the lower 10% of all CVEs scored today.
EPSS score
0.1 %
Low — model estimates < 1% exploitation likelihood.
Published
2026-09-07 09:05 UTC
CWE
—

Reanalysis & status changes

Chronological NVD audit events for this CVE — reanalyses, CVSS updates, CPE diffs.

  1. Initial Analysis2026-07-07 20:10 UTC· nvd@nist.gov
    • CVSS V3.1: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
    • CWE: NVD-CWE-noinfo
    • CPE Configuration: OR *cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc3:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc4:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.19 up to (excluding) 7.0.13 *cpe:2.3:o:linux:linux_kernel:7.1:rc5:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc6:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc7:*:*:*:*:*:*
    • Reference Type: kernel.org: https://git.kernel.org/stable/c/43e7f189769c512c843184a8a5892ac779a6bd90 Types: Patch

Affected operating systems

  • linux

    redhat / enterprise_linux10.0

  • linux

    redhat / enterprise_linux7.0

  • linux

    redhat / enterprise_linux8.0

  • linux

    redhat / enterprise_linux9.0

  • linux

    ubuntu / linux-aws-6.8jammy

  • linux

    ubuntu / linux-azureresolute

  • linux

    ubuntu / linux-azuretrusty

  • linux

    ubuntu / linux-azurexenial

  • linux

    ubuntu / linux-azure-4.15bionic

  • linux

    ubuntu / linux-azure-5.4bionic

  • linux

    ubuntu / linux-azure-fdenoble

  • linux

    ubuntu / linux-azure-fderesolute

  • linux

    ubuntu / linux-azure-fde-6.8jammy

  • linux

    ubuntu / linux-azure-fipsbionic

  • linux

    ubuntu / linux-azure-fipsfocal

  • linux

    ubuntu / linux-azure-fipsnoble

  • linux

    ubuntu / linux-fipsjammy

  • linux

    ubuntu / linux-gcp-7.0noble

  • linux

    ubuntu / linux-gkejammy

  • linux

    ubuntu / linux-nvidia-tegranoble

  • linux

    ubuntu / linux-raspinoble

  • linux

    ubuntu / linux-raspi-realtimenoble

  • linux

    linux / linux_kernel2.6.12

  • linux

    linux / linux_kernel2.6.15

References & sources

Linked CVEs

Show 1392 more CVEs
IDCVE-2026-53155
Linux kernel (GCP) vulnerabilities — CVE-2026-53155 | NEOSEC Intel