CVE-2023-53823 (GCVE-0-2023-53823)
Vulnerability from cvelistv5
Published
2025-12-09 01:29
Modified
2026-08-05 09:16
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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_no_open() from blkg_conf_open_bdev(), and is released in blkg_conf_exit(). In order to fix the above memory leak, disk_live() is checked after holding the new lock.
References
Impacted products
Vendor Product Version
Linux Linux Version: 50e34d78815e474d410f342fbe783b18192ca518
Version: 50e34d78815e474d410f342fbe783b18192ca518
Version: f28699fafc047ec33299da01e928c3a0073c5cc6
Version: 5.18.8   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "block/blk-cgroup.c",
            "block/blk-core.c",
            "block/blk-rq-qos.c",
            "block/blk-wbt.c",
            "include/linux/blkdev.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "16398b4638b5cd8c1dc95fc940a1591a801d53ce",
              "status": "affected",
              "version": "50e34d78815e474d410f342fbe783b18192ca518",
              "versionType": "git"
            },
            {
              "lessThan": "a13bd91be22318768d55470cbc0b0f4488ef9edf",
              "status": "affected",
              "version": "50e34d78815e474d410f342fbe783b18192ca518",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "f28699fafc047ec33299da01e928c3a0073c5cc6",
              "versionType": "git"
            },
            {
              "lessThan": "5.19",
              "status": "affected",
              "version": "5.18.8",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "block/blk-cgroup.c",
            "block/blk-core.c",
            "block/blk-rq-qos.c",
            "block/blk-wbt.c",
            "include/linux/blkdev.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.19"
            },
            {
              "lessThan": "5.19",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.4.*",
              "status": "unaffected",
              "version": "6.4.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.5",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.4.4",
                  "versionStartIncluding": "5.19",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.5",
                  "versionStartIncluding": "5.19",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "5.18.8",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nblock/rq_qos: protect rq_qos apis with a new lock\n\ncommit 50e34d78815e (\"block: disable the elevator int del_gendisk\")\nmove rq_qos_exit() from disk_release() to del_gendisk(), this will\nintroduce some problems:\n\n1) If rq_qos_add() is triggered by enabling iocost/iolatency through\n   cgroupfs, then it can concurrent with del_gendisk(), it\u0027s not safe to\n   write \u0027q-\u003erq_qos\u0027 concurrently.\n\n2) Activate cgroup policy that is relied on rq_qos will call\n   rq_qos_add() and blkcg_activate_policy(), and if rq_qos_exit() is\n   called in the middle, null-ptr-dereference will be triggered in\n   blkcg_activate_policy().\n\n3) blkg_conf_open_bdev() can call blkdev_get_no_open() first to find the\n   disk, then if rq_qos_exit() from del_gendisk() is done before\n   rq_qos_add(), then memory will be leaked.\n\nThis patch add a new disk level mutex \u0027rq_qos_mutex\u0027:\n\n1) The lock will protect rq_qos_exit() directly.\n\n2) For wbt that doesn\u0027t relied on blk-cgroup, rq_qos_add() can only be\n   called from disk initialization for now because wbt can\u0027t be\n   destructed until rq_qos_exit(), so it\u0027s safe not to protect wbt for\n   now. Hoever, in case that rq_qos dynamically destruction is supported\n   in the furture, this patch also protect rq_qos_add() from wbt_init()\n   directly, this is enough because blk-sysfs already synchronize\n   writers with disk removal.\n\n3) For iocost and iolatency, in order to synchronize disk removal and\n   cgroup configuration, the lock is held after blkdev_get_no_open()\n   from blkg_conf_open_bdev(), and is released in blkg_conf_exit().\n   In order to fix the above memory leak, disk_live() is checked after\n   holding the new lock."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Both sides of the race are driven through local interfaces \u2014 a cgroupfs write to `io.latency`/`io.cost.qos` reaching `rq_qos_add()`, and a block-device removal reaching `del_gendisk()`\u2192`rq_qos_exit()`. There is no remote or network-facing path into the block rq_qos layer.\nAC:L - The attacker controls both sides: they can loop the `io.latency` write against any device by MAJ:MIN (no permission check in `blkg_conf_open_bdev()`) while triggering repeated disk teardown (loop/nbd device delete), and can stretch the `rq_qos_add()`\u2192`timer_setup()` window arbitrarily by populating the queue with thousands of blkgs so `blkcg_activate_policy()` spends a long time in GFP_KERNEL allocation and retry.\nPR:L - No capability check exists on the path \u2014 `iolatency_set_limit()`/`blkg_conf_open_bdev()` gate only on cgroupfs file permissions, and `cgroup_add_file()` creates interface files owned by `current_fsuid()`, so an unprivileged user with a delegated cgroup v2 subtree (systemd delegation, container runtimes) can write `io.latency` and target any block device on the system.\nUI:N - The attacker performs both the cgroup configuration write and the disk removal themselves; no action by any other user or administrator is needed.\nS:U - The corruption is confined to kernel heap objects and the block layer\u0027s request_queue within the same security authority; there is no crossing of a VM, IOMMU, or sandbox boundary.\nC:H - The unsynchronized `q-\u003erq_qos` update leaves freed `rq_qos` objects linked in the chain and dangling `blk_iolatency`/gendisk pointers, giving a use-after-free read primitive over reclaimed slab memory that can be groomed to disclose arbitrary kernel data.\nI:H - `blk_iolatency_init()` continues writing (`timer_setup()`, `INIT_WORK()`) into the object already freed by `blkcg_iolatency_exit()`, and `__rq_qos_throttle()` performs an indirect call through `rqos-\u003eops-\u003ethrottle` read from freed memory \u2014 a heap-spray-controllable arbitrary write and control-flow hijack.\nA:H - The race reliably produces kernel oopses \u2014 a NULL dereference through `iolat-\u003eblkiolat` set to NULL by `iolatency_pd_init()`, plus use-after-free faults on the rq_qos chain during I/O submission and from the leaked object\u0027s timer firing after the disk is released."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T09:16:14.720Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/16398b4638b5cd8c1dc95fc940a1591a801d53ce"
        },
        {
          "url": "https://git.kernel.org/stable/c/a13bd91be22318768d55470cbc0b0f4488ef9edf"
        }
      ],
      "title": "block/rq_qos: protect rq_qos apis with a new lock",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2023-53823",
    "datePublished": "2025-12-09T01:29:36.343Z",
    "dateReserved": "2025-12-09T01:27:17.824Z",
    "dateUpdated": "2026-08-05T09:16:14.720Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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