usb: gadget: f_ncm: Fix net_device lifecycle with device_move

{
  "id": "a127615e9de4b7c2164a18be8abe6a80db4b5322dcc2723e0956e39127ca8ca3",
  "url": "https://osv.dev/vulnerability/CVE-2026-43421",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "usb: gadget: f_ncm: Fix net_device lifecycle with device_move",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_ncm: Fix net_device lifecycle with device_move The network device outlived its parent gadget device during disconnection, resulting in dangling sysfs links and null pointer dereference problems. A prior attempt to solve this by removing SET_NETDEV_DEV entirely [1] was reverted due to power management ordering concerns and a NO-CARRIER regression. A subsequent attempt to defer net_device allocation to bind [2] broke 1:1 mapping between function instance and network device, making it impossible for configfs to report the resolved interface name. This results in a regression where the DHCP server fails on pmOS. Use device_move to reparent the net_device between the gadget device and /sys/devices/virtual/ across bind/unbind cycles. This preserves the network interface across USB reconnection, allowing the DHCP server to retain their binding. Introduce gether_attach_gadget()/gether_detach_gadget() helpers and use __free(detach_gadget) macro to undo attachment on bind failure. The bind_count ensures device_move executes only on the first bind. [1] https://lore.kernel.org/lkml/f2a4f9847617a0929d62025748384092e5f35cce.camel@crapouillou.net/ [2] https://lore.kernel.org/linux-usb/795ea759-7eaf-4f78-81f4-01ffbf2d7961@ixit.cz/",
    "evidence": "osv:CVE-2026-43421",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
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            "value": "6.1.176",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.143",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.78",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.19",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.9",
            "evidence": "/affected/1/ranges"
          }
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        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-43421",
      "aliases": [
        "CVE-2026-43421"
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                  "fixed": "e584cb58a2ea7ff4d3a4bc43d5ca512ed3ecb77d"
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          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43421.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:50.183800399Z",
      "provider": "osv",
      "references": [
        "https://cert-portal.siemens.com/productcert/html/ssa-784472.html",
        "https://git.kernel.org/stable/c/36c41e9724c9a7a7cda37f5a4e9d94f25c8031c4",
        "https://git.kernel.org/stable/c/7c97366f5dac5255e60a317ffe3a5b18f3745547",
        "https://git.kernel.org/stable/c/85acaba2f42b557499bab3608307f17bf13beb69",
        "https://git.kernel.org/stable/c/93f116c3393a22acab96ad1bef12b2572eb80ca4",
        "https://git.kernel.org/stable/c/e584cb58a2ea7ff4d3a4bc43d5ca512ed3ecb77d",
        "https://git.kernel.org/stable/c/ec35c1969650e7cb6c8a91020e568ed46e3551b0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43421.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-43421",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43421.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-43421",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 518237,
  "published_at": "2026-05-08T14:21:56.363+00:00"
}