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CVE-2026-68163 (GCVE-0-2026-68163)

Vulnerability from cvelistv5 – Published: 2026-08-10 11:59 – Updated: 2026-08-17 05:00
VLAI
Title
mm/page_vma_mapped: fix device-private PMD handling
Summary
In the Linux kernel, the following vulnerability has been resolved: mm/page_vma_mapped: fix device-private PMD handling Commit 65edfda6f3f2 ("mm/rmap: extend rmap and migration support device-private entries") introduced the concept of device-private PMD entries, but did not correctly update the rmap walk code to account for them. As a result, when page_vma_mapped_walk() encounters device-private PMD entries, it takes no action other than to acquire the PMD lock and exit. However this is highly problematic for two reasons - firstly, device private entries possess a PFN so check_pmd() needs to be called to ensure an overlapping PFN range. Secondly, and more importantly, if PVMW_MIGRATION is set the caller assumes the returned entry is a migration entry, resulting in memory corruption when the caller tries to interpret the device private entry as such. In addition, commit 146287290023 ("mm/huge_memory: implement device-private THP splitting") allowed device private PMDs to be split like THP mappings, but again did not update this code path. As a result, we might race a PMD split prior to acquiring the PMD lock. This patch addresses all of these issues by invoking check_pmd(), ensuring PMVW_MIGRATION is not set and checks whether a split raced us we do for PMD THP and migration entries. Instead of checking for a subset of the cases after taking the pmd_lock(), put device-private along with pmd_trans_huge() and pmd_is_migration_entry(). Also remove thp_migration_supported() as it is already guarded by pmd_is_migration_entry(). [akpm@linux-foundation.org: fix Raspberry Pi 1 build, per David]
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 65edfda6f3f2e58f757485a056e4f1775a1404a8 , < ab6209f4b48a98ef14d6766acdb62aa9bb32e670 (git)
Affected: 65edfda6f3f2e58f757485a056e4f1775a1404a8 , < f84ca9b1888d8fce7dfefe0e750fa971f8797486 (git)
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Linux Linux Affected: 6.19
Unaffected: 0 , < 6.19 (semver)
Unaffected: 7.1.6 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/page_vma_mapped: fix device-private PMD handling\n\nCommit 65edfda6f3f2 (\"mm/rmap: extend rmap and migration support\ndevice-private entries\") introduced the concept of device-private PMD\nentries, but did not correctly update the rmap walk code to account for\nthem.\n\nAs a result, when page_vma_mapped_walk() encounters device-private PMD\nentries, it takes no action other than to acquire the PMD lock and exit.\n\nHowever this is highly problematic for two reasons - firstly, device\nprivate entries possess a PFN so check_pmd() needs to be called to ensure\nan overlapping PFN range.\n\nSecondly, and more importantly, if PVMW_MIGRATION is set the caller\nassumes the returned entry is a migration entry, resulting in memory\ncorruption when the caller tries to interpret the device private entry as\nsuch.\n\nIn addition, commit 146287290023 (\"mm/huge_memory: implement\ndevice-private THP splitting\") allowed device private PMDs to be split\nlike THP mappings, but again did not update this code path.\n\nAs a result, we might race a PMD split prior to acquiring the PMD lock.\n\nThis patch addresses all of these issues by invoking check_pmd(), ensuring\nPMVW_MIGRATION is not set and checks whether a split raced us we do for\nPMD THP and migration entries.\n\nInstead of checking for a subset of the cases after taking the pmd_lock(),\nput device-private along with pmd_trans_huge() and\npmd_is_migration_entry().  Also remove thp_migration_supported() as it is\nalready guarded by pmd_is_migration_entry().\n\n[akpm@linux-foundation.org: fix Raspberry Pi 1 build, per David]"
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              "value": "AV:L - The bug is in the MM rmap/page-table walk reached only from in-kernel memory-management paths (migrate_vma finalize, rmap unmap/migration) triggered by local syscalls and GPU driver ioctls (AMD KFD, nouveau, drm_pagemap), not from network packet handling.\nAC:L - An attacker with GPU/HMM access can reliably create device-private THP PMDs and drive migrate_vma/setup/finalize while racing PMD splits via concurrent threads; both sides of the race are attacker-controlled, not dependent on admin timing or uncontrollable layout.\nPR:L - Exploitation needs only an unprivileged local user who can use the GPU/HMM stack (typical render/video group access on ML/cloud GPU nodes) to allocate device-private THP and invoke migration; it does not require real root in the init namespace.\nUI:N - No victim interaction is required; memory migration and PMD splitting are driven entirely by the attacker\u0027s own process through normal GPU unified-memory/migration APIs and concurrent threads.\nS:U - Impact is kernel page-table corruption and local privilege escalation within the host kernel security domain; it is not a VM guest-to-host escape, IOMMU bypass, or cross-authority sandbox breakout per kernel CVSS scope guidance.\nC:H - Misinterpreting a device-private PMD as a migration entry corrupts page tables and rmap state; such MM corruption is readily weaponizable for arbitrary kernel memory reads, not merely a bounded leak.\nI:H - The faulty walk causes remove_migration_pmd() and related callers to install incorrect PMD/PTE contents from mis-typed entries, enabling arbitrary kernel memory writes and control-flow hijack via page-table manipulation.\nA:H - Incorrect PMD handling during migration or concurrent THP splitting can cause kernel oops/panic, use-after-free conditions, or hung migration paths, producing full system denial of service even before successful exploitation."
            }
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    "cveId": "CVE-2026-68163",
    "datePublished": "2026-08-10T11:59:30.633Z",
    "dateReserved": "2026-07-30T09:28:09.372Z",
    "dateUpdated": "2026-08-17T05:00:02.619Z",
    "state": "PUBLISHED"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-31T11:17:43+00:00",
      "cve": "CVE-2026-68163",
      "id": "CVE-2026-68163",
      "initial_release_date": "2026-08-10T00:00:00+00:00",
      "product_status:known_not_affected": "277",
      "source": "Red Hat CSAF VEX",
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      "title": "kernel: mm/page_vma_mapped: fix device-private PMD handling",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-68163.json",
      "version": "3"
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    "suse_vex": {
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      "current_release_date": "2026-08-13T16:23:59Z",
      "cve": "CVE-2026-68163",
      "id": "CVE-2026-68163",
      "initial_release_date": "2026-08-13T16:23:59Z",
      "product_status:known_affected": "29",
      "product_status:known_not_affected": "267",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-68163",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-68163.json",
      "version": "2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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