xenbus: Use kref to track req lifetime

{
  "id": "6e6c86f5fb4d77dd4efa489377abc91a859af8cae698687a2417dc6786ad47f2",
  "url": "https://osv.dev/vulnerability/CVE-2025-37949",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "xenbus: Use kref to track req lifetime",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: xenbus: Use kref to track req lifetime Marek reported seeing a NULL pointer fault in the xenbus_thread callstack: BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: e030:__wake_up_common+0x4c/0x180 Call Trace: __wake_up_common_lock+0x82/0xd0 process_msg+0x18e/0x2f0 xenbus_thread+0x165/0x1c0 process_msg+0x18e is req->cb(req). req->cb is set to xs_wake_up(), a thin wrapper around wake_up(), or xenbus_dev_queue_reply(). It seems like it was xs_wake_up() in this case. It seems like req may have woken up the xs_wait_for_reply(), which kfree()ed the req. When xenbus_thread resumes, it faults on the zero-ed data. Linux Device Drivers 2nd edition states: \"Normally, a wake_up call can cause an immediate reschedule to happen, meaning that other processes might run before wake_up returns.\" ... which would match the behaviour observed. Change to keeping two krefs on each request. One for the caller, and one for xenbus_thread. Each will kref_put() when finished, and the last will free it. This use of kref matches the description in Documentation/core-api/kref.rst",
    "evidence": "osv:CVE-2025-37949",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.4.294",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.10.238",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.183",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.139",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.91",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.29",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.14.7",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2025-37949",
      "aliases": [
        "CVE-2025-37949"
      ],
      "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": [
                {
                  "introduced": "fd8aa9095a95c02dcc35540a263267c29b8fda9d"
                },
                {
                  "fixed": "0e94a246bb6d9538010b6c02d2b1d4717a97b2e5"
                },
                {
                  "fixed": "f1bcac367bc95631afbb918348f30dec887d0e1b"
                },
                {
                  "fixed": "4d260a5558df4650eb87bc41b2c9ac2d6b2ba447"
                },
                {
                  "fixed": "8b02f85e84dc6f7c150cef40ddb69af5a25659e5"
                },
                {
                  "fixed": "cbfaf46b88a4c01b64c4186cdccd766c19ae644c"
                },
                {
                  "fixed": "8e9c8a0393b5f85f1820c565ab8105660f4e8f92"
                },
                {
                  "fixed": "2466b0f66795c3c426cacc8998499f38031dbb59"
                },
                {
                  "fixed": "1f0304dfd9d217c2f8b04a9ef4b3258a66eedd27"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-37949.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "4.11.0"
                },
                {
                  "fixed": "5.4.294"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.5.0"
                },
                {
                  "fixed": "5.10.238"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.11.0"
                },
                {
                  "fixed": "5.15.183"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.16.0"
                },
                {
                  "fixed": "6.1.139"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.91"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.29"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.14.7"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-37949.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:41.330286338Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/0e94a246bb6d9538010b6c02d2b1d4717a97b2e5",
        "https://git.kernel.org/stable/c/1f0304dfd9d217c2f8b04a9ef4b3258a66eedd27",
        "https://git.kernel.org/stable/c/2466b0f66795c3c426cacc8998499f38031dbb59",
        "https://git.kernel.org/stable/c/4d260a5558df4650eb87bc41b2c9ac2d6b2ba447",
        "https://git.kernel.org/stable/c/8b02f85e84dc6f7c150cef40ddb69af5a25659e5",
        "https://git.kernel.org/stable/c/8e9c8a0393b5f85f1820c565ab8105660f4e8f92",
        "https://git.kernel.org/stable/c/cbfaf46b88a4c01b64c4186cdccd766c19ae644c",
        "https://git.kernel.org/stable/c/f1bcac367bc95631afbb918348f30dec887d0e1b",
        "https://lists.debian.org/debian-lts-announce/2025/08/msg00010.html",
        "https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/37xxx/CVE-2025-37949.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-37949",
        "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/2025/37xxx/CVE-2025-37949.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-37949",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 508813,
  "published_at": "2025-05-20T16:01:45.242+00:00"
}