CVE-2026-31530 (GCVE-0-2026-31530)

Vulnerability from cvelistv5 – Published: 2026-04-22 13:54 – Updated: 2026-11-05 21:45
VLAI
Title
cxl/port: Fix use after free of parent_port in cxl_detach_ep()
Summary
In the Linux kernel, the following vulnerability has been resolved: cxl/port: Fix use after free of parent_port in cxl_detach_ep() cxl_detach_ep() is called during bottom-up removal when all CXL memory devices beneath a switch port have been removed. For each port in the hierarchy it locks both the port and its parent, removes the endpoint, and if the port is now empty, marks it dead and unregisters the port by calling delete_switch_port(). There are two places during this work where the parent_port may be used after freeing: First, a concurrent detach may have already processed a port by the time a second worker finds it via bus_find_device(). Without pinning parent_port, it may already be freed when we discover port->dead and attempt to unlock the parent_port. In a production kernel that's a silent memory corruption, with lock debug, it looks like this: []DEBUG_LOCKS_WARN_ON(__owner_task(owner) != get_current()) []WARNING: kernel/locking/mutex.c:949 at __mutex_unlock_slowpath+0x1ee/0x310 []Call Trace: []mutex_unlock+0xd/0x20 []cxl_detach_ep+0x180/0x400 [cxl_core] []devm_action_release+0x10/0x20 []devres_release_all+0xa8/0xe0 []device_unbind_cleanup+0xd/0xa0 []really_probe+0x1a6/0x3e0 Second, delete_switch_port() releases three devm actions registered against parent_port. The last of those is unregister_port() and it calls device_unregister() on the child port, which can cascade. If parent_port is now also empty the device core may unregister and free it too. So by the time delete_switch_port() returns, parent_port may be free, and the subsequent device_unlock(&parent_port->dev) operates on freed memory. The kernel log looks same as above, with a different offset in cxl_detach_ep(). Both of these issues stem from the absence of a lifetime guarantee between a child port and its parent port. Establish a lifetime rule for ports: child ports hold a reference to their parent device until release. Take the reference when the port is allocated and drop it when released. This ensures the parent is valid for the full lifetime of the child and eliminates the use after free window in cxl_detach_ep(). This is easily reproduced with a reload of cxl_acpi in QEMU with CXL devices present.
Severity
No CVSS data available.
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-11-05 21:37 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6641 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 2345df54249c6fb7779e2a72b427ee79ed3eaad5 , < b1f62588ab1be6c9535d74348003c86b47ec4abd (git)
Affected: 2345df54249c6fb7779e2a72b427ee79ed3eaad5 , < d216a4bd138eb57cc4ae7c43b2f709e3482af7e2 (git)
Affected: 2345df54249c6fb7779e2a72b427ee79ed3eaad5 , < 2c32141462045cf93d54a5146a0ba572b83533dd (git)
Affected: 2345df54249c6fb7779e2a72b427ee79ed3eaad5 , < f7dc6f381a1e5f068333f1faa9265d6af1df4235 (git)
Affected: 2345df54249c6fb7779e2a72b427ee79ed3eaad5 , < 19d2f0b97a131198efc2c4ca3eb7f980bba8c2b4 (git)
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Linux Linux Affected: 6.3
Unaffected: 0 , < 6.3 (semver)
Unaffected: 6.6.160 , ≤ 6.6.* (semver)
Unaffected: 6.12.80 , ≤ 6.12.* (semver)
Unaffected: 6.18.21 , ≤ 6.18.* (semver)
Unaffected: 6.19.11 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\ncxl/port: Correcci\u00f3n de uso despu\u00e9s de liberaci\u00f3n de parent_port en cxl_detach_ep()\n\ncxl_detach_ep() es llamada durante la eliminaci\u00f3n de abajo hacia arriba cuando todos los dispositivos de memoria CXL debajo de un puerto de switch han sido eliminados. Para cada puerto en la jerarqu\u00eda, bloquea tanto el puerto como su padre, elimina el punto final, y si el puerto ahora est\u00e1 vac\u00edo, lo marca como muerto y anula el registro del puerto llamando a delete_switch_port(). Hay dos lugares durante este trabajo donde parent_port puede ser usado despu\u00e9s de su liberaci\u00f3n:\n\nPrimero, una desconexi\u00f3n concurrente puede haber procesado ya un puerto para cuando un segundo trabajador lo encuentra a trav\u00e9s de bus_find_device(). Sin fijar parent_port, puede que ya est\u00e9 liberado cuando descubrimos port  -\u003e  dead e intentamos desbloquear parent_port. En un kernel de producci\u00f3n eso es una corrupci\u00f3n de memoria silenciosa, con depuraci\u00f3n de bloqueo, se ve as\u00ed:\n\nDEBUG_LOCKS_WARN_ON(__owner_task(owner) != get_current())\nWARNING: kernel/locking/mutex.c:949 at __mutex_unlock_slowpath+0x1ee/0x310\nTraza de Llamada:\nmutex_unlock+0xd/0x20\ncxl_detach_ep+0x180/0x400 [cxl_core]\ndevm_action_release+0x10/0x20\ndevres_release_all+0xa8/0xe0\ndevice_unbind_cleanup+0xd/0xa0\nreally_probe+0x1a6/0x3e0\n\nSegundo, delete_switch_port() libera tres acciones devm registradas contra parent_port. La \u00faltima de ellas es unregister_port() y llama a device_unregister() en el puerto hijo, lo que puede generar una cascada. Si parent_port ahora tambi\u00e9n est\u00e1 vac\u00edo el n\u00facleo del dispositivo puede anular su registro y liberarlo tambi\u00e9n. As\u00ed que para cuando delete_switch_port() regresa, parent_port puede estar libre, y el subsiguiente device_unlock(ref:parent_port  -\u003e  dev) opera sobre memoria liberada. El registro del kernel se ve igual que el anterior, con un desplazamiento diferente en cxl_detach_ep().\n\nAmbos de estos problemas provienen de la ausencia de una garant\u00eda de vida \u00fatil entre un puerto hijo y su puerto padre.\n\nEstablecer una regla de vida \u00fatil para los puertos: los puertos hijos mantienen una referencia a su dispositivo padre hasta su liberaci\u00f3n. Tomar la referencia cuando el puerto es asignado y soltarla cuando es liberado. Esto asegura que el padre sea v\u00e1lido durante toda la vida \u00fatil del hijo y elimina la ventana de uso despu\u00e9s de liberaci\u00f3n en cxl_detach_ep().\n\nEsto se reproduce f\u00e1cilmente con una recarga de cxl_acpi en QEMU con dispositivos CXL presentes."
          }
        ],
        "id": "CVE-2026-31530",
        "lastModified": "2026-11-11T23:10:00.263",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "nvd@nist.gov",
              "type": "Primary"
            }
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                  {
                    "technicalImpact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-11-05T21:37:47.922657Z",
                "version": "2.0.3"
              }
            }
          ]
        },
        "published": "2026-04-22T14:16:53.293",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
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            "url": "https://git.kernel.org/stable/c/19d2f0b97a131198efc2c4ca3eb7f980bba8c2b4"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Modified",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-416"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
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      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-11-09T17:51:22+00:00",
      "cve": "CVE-2026-31530",
      "id": "CVE-2026-31530",
      "initial_release_date": "2026-04-22T00:00:00+00:00",
      "product_status:fixed": "612",
      "product_status:known_not_affected": "112",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: cxl/port: Fix use after free of parent_port in cxl_detach_ep()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31530.json",
      "version": "3"
    },
    "vulnrichment": {
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          {
            "metrics": [
              {
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                  "content": {
                    "id": "CVE-2026-31530",
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                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-11-05T21:37:47.922657Z",
                    "version": "2.0.3"
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                  "type": "ssvc"
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              }
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            "providerMetadata": {
              "dateUpdated": "2026-11-05T21:37:49.615Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
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              "defaultStatus": "unaffected",
              "product": "Linux",
              "programFiles": [
                "drivers/cxl/core/port.c"
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
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                {
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                {
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            },
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              "product": "Linux",
              "programFiles": [
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              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
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                  "status": "affected",
                  "version": "6.3"
                },
                {
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                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                },
                {
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                  "status": "unaffected",
                  "version": "6.6.160",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.12.*",
                  "status": "unaffected",
                  "version": "6.12.80",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.18.*",
                  "status": "unaffected",
                  "version": "6.18.21",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.19.*",
                  "status": "unaffected",
                  "version": "6.19.11",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "7.0",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
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              "nodes": [
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                  "cpeMatch": [
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                      "vulnerable": true
                    },
                    {
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                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncxl/port: Fix use after free of parent_port in cxl_detach_ep()\n\ncxl_detach_ep() is called during bottom-up removal when all CXL memory\ndevices beneath a switch port have been removed. For each port in the\nhierarchy it locks both the port and its parent, removes the endpoint,\nand if the port is now empty, marks it dead and unregisters the port\nby calling delete_switch_port(). There are two places during this work\nwhere the parent_port may be used after freeing:\n\nFirst, a concurrent detach may have already processed a port by the\ntime a second worker finds it via bus_find_device(). Without pinning\nparent_port, it may already be freed when we discover port-\u003edead and\nattempt to unlock the parent_port. In a production kernel that\u0027s a\nsilent memory corruption, with lock debug, it looks like this:\n\n[]DEBUG_LOCKS_WARN_ON(__owner_task(owner) != get_current())\n[]WARNING: kernel/locking/mutex.c:949 at __mutex_unlock_slowpath+0x1ee/0x310\n[]Call Trace:\n[]mutex_unlock+0xd/0x20\n[]cxl_detach_ep+0x180/0x400 [cxl_core]\n[]devm_action_release+0x10/0x20\n[]devres_release_all+0xa8/0xe0\n[]device_unbind_cleanup+0xd/0xa0\n[]really_probe+0x1a6/0x3e0\n\nSecond, delete_switch_port() releases three devm actions registered\nagainst parent_port. The last of those is unregister_port() and it\ncalls device_unregister() on the child port, which can cascade. If\nparent_port is now also empty the device core may unregister and free\nit too. So by the time delete_switch_port() returns, parent_port may\nbe free, and the subsequent device_unlock(\u0026parent_port-\u003edev) operates\non freed memory. The kernel log looks same as above, with a different\noffset in cxl_detach_ep().\n\nBoth of these issues stem from the absence of a lifetime guarantee\nbetween a child port and its parent port.\n\nEstablish a lifetime rule for ports: child ports hold a reference to\ntheir parent device until release. Take the reference when the port\nis allocated and drop it when released. This ensures the parent is\nvalid for the full lifetime of the child and eliminates the use after\nfree window in cxl_detach_ep().\n\nThis is easily reproduced with a reload of cxl_acpi in QEMU with CXL\ndevices present."
            }
          ],
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            "dateUpdated": "2026-10-21T12:39:25.498Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
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          "references": [
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            },
            {
              "url": "https://git.kernel.org/stable/c/d216a4bd138eb57cc4ae7c43b2f709e3482af7e2"
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            {
              "url": "https://git.kernel.org/stable/c/19d2f0b97a131198efc2c4ca3eb7f980bba8c2b4"
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          ],
          "title": "cxl/port: Fix use after free of parent_port in cxl_detach_ep()",
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        "assignerShortName": "Linux",
        "cveId": "CVE-2026-31530",
        "datePublished": "2026-04-22T13:54:42.563Z",
        "dateReserved": "2026-03-09T15:48:24.112Z",
        "dateUpdated": "2026-11-05T21:45:06.495Z",
        "state": "PUBLISHED"
      },
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  }
}



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