block/rq_qos: protect rq_qos apis with a new lock

{
  "id": "f0f27236b24651f368c5d765bcc7507fc9e2855c805051c1883c9fc72d97ae1a",
  "url": "https://osv.dev/vulnerability/CVE-2023-53823",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "block/rq_qos: protect rq_qos apis with a new lock",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: block/rq_qos: protect rq_qos apis with a new lock commit 50e34d78815e (\"block: disable the elevator int del_gendisk\") move rq_qos_exit() from disk_release() to del_gendisk(), this will introduce some problems: 1) If rq_qos_add() is triggered by enabling iocost/iolatency through cgroupfs, then it can concurrent with del_gendisk(), it's not safe to write 'q->rq_qos' concurrently. 2) Activate cgroup policy that is relied on rq_qos will call rq_qos_add() and blkcg_activate_policy(), and if rq_qos_exit() is called in the middle, null-ptr-dereference will be triggered in blkcg_activate_policy(). 3) blkg_conf_open_bdev() can call blkdev_get_no_open() first to find the disk, then if rq_qos_exit() from del_gendisk() is done before rq_qos_add(), then memory will be leaked. This patch add a new disk level mutex 'rq_qos_mutex': 1) The lock will protect rq_qos_exit() directly. 2) For wbt that doesn't relied on blk-cgroup, rq_qos_add() can only be called from disk initialization for now because wbt can't be destructed until rq_qos_exit(), so it's safe not to protect wbt for now. Hoever, in case that rq_qos dynamically destruction is supported in the furture, this patch also protect rq_qos_add() from wbt_init() directly, this is enough because blk-sysfs already synchronize writers with disk removal. 3) For iocost and iolatency, in order to synchronize disk removal and cgroup configuration, the lock is held after blkdev_get_",
    "evidence": "osv:CVE-2023-53823",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.4.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2023-53823",
      "aliases": [
        "CVE-2023-53823"
      ],
      "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": [
        {
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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            "v5.18.9",
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-53823.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.19.0"
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                {
                  "fixed": "6.4.4"
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              ]
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          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-53823.json"
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      ],
      "modified": "2026-10-08T02:48:13.161946159Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/16398b4638b5cd8c1dc95fc940a1591a801d53ce",
        "https://git.kernel.org/stable/c/a13bd91be22318768d55470cbc0b0f4488ef9edf",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/53xxx/CVE-2023-53823.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2023-53823",
        "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/2023/53xxx/CVE-2023-53823.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2023-53823",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 98272,
  "published_at": "2025-12-09T01:29:36.343+00:00"
}