gpib: fix use-after-free in IO ioctl handlers

{
  "id": "63b2e768b99c1dd6d2ed171d61a6080231ead20d9434d5a38efe4e1b976fda70",
  "url": "https://osv.dev/vulnerability/CVE-2026-31769",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "gpib: fix use-after-free in IO ioctl handlers",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: gpib: fix use-after-free in IO ioctl handlers The IBRD, IBWRT, IBCMD, and IBWAIT ioctl handlers use a gpib_descriptor pointer after board->big_gpib_mutex has been released. A concurrent IBCLOSEDEV ioctl can free the descriptor via close_dev_ioctl() during this window, causing a use-after-free. The IO handlers (read_ioctl, write_ioctl, command_ioctl) explicitly release big_gpib_mutex before calling their handler. wait_ioctl() is called with big_gpib_mutex held, but ibwait() releases it internally when wait_mask is non-zero. In all four cases, the descriptor pointer obtained from handle_to_descriptor() becomes unprotected. Fix this by introducing a kernel-only descriptor_busy reference count in struct gpib_descriptor. Each handler atomically increments descriptor_busy under file_priv->descriptors_mutex before releasing the lock, and decrements it when done. close_dev_ioctl() checks descriptor_busy under the same lock and rejects the close with -EBUSY if the count is non-zero. A reference count rather than a simple flag is necessary because multiple handlers can operate on the same descriptor concurrently (e.g. IBRD and IBWAIT on the same handle from different threads). A separate counter is needed because io_in_progress can be cleared from unprivileged userspace via the IBWAIT ioctl (through general_ibstatus() with set_mask containing CMPL), which would allow an attacker to bypass a check based solely on io_in_",
    "evidence": "osv:CVE-2026-31769",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.18.22",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.12",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-31769",
      "aliases": [
        "CVE-2026-31769"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                  "introduced": "9dde4559e93955ccc47d588f7fd051684d55c4e7"
                },
                {
                  "fixed": "cae26eff1b56d78bed7873cf3e60a2b1bdd4da6c"
                },
                {
                  "fixed": "28c75dd143ead62e0dfac564c79d251e21d5d74b"
                },
                {
                  "fixed": "d1857f8296dceb75d00ab857fc3c61bc00c7f5c6"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31769.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.22"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "6.19.12"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31769.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:44.114510299Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/28c75dd143ead62e0dfac564c79d251e21d5d74b",
        "https://git.kernel.org/stable/c/cae26eff1b56d78bed7873cf3e60a2b1bdd4da6c",
        "https://git.kernel.org/stable/c/d1857f8296dceb75d00ab857fc3c61bc00c7f5c6",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31769.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-31769",
        "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/2026/31xxx/CVE-2026-31769.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-31769",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 511659,
  "published_at": "2026-05-01T14:14:58.617+00:00"
}