CVE-2025-71070 (GCVE-0-2025-71070)
Vulnerability from cvelistv5
Published
2026-01-13 15:31
Modified
2026-08-05 12:11
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: ublk: clean up user copy references on ublk server exit If a ublk server process releases a ublk char device file, any requests dispatched to the ublk server but not yet completed will retain a ref value of UBLK_REFCOUNT_INIT. Before commit e63d2228ef83 ("ublk: simplify aborting ublk request"), __ublk_fail_req() would decrement the reference count before completing the failed request. However, that commit optimized __ublk_fail_req() to call __ublk_complete_rq() directly without decrementing the request reference count. The leaked reference count incorrectly allows user copy and zero copy operations on the completed ublk request. It also triggers the WARN_ON_ONCE(refcount_read(&io->ref)) warnings in ublk_queue_reinit() and ublk_deinit_queue(). Commit c5c5eb24ed61 ("ublk: avoid ublk_io_release() called after ublk char dev is closed") already fixed the issue for ublk devices using UBLK_F_SUPPORT_ZERO_COPY or UBLK_F_AUTO_BUF_REG. However, the reference count leak also affects UBLK_F_USER_COPY, the other reference-counted data copy mode. Fix the condition in ublk_check_and_reset_active_ref() to include all reference-counted data copy modes. This ensures that any ublk requests still owned by the ublk server when it exits have their reference counts reset to 0.
References
Impacted products
Vendor Product Version
Linux Linux Version: e63d2228ef831af36f963b3ab8604160cfff84c1
Version: e63d2228ef831af36f963b3ab8604160cfff84c1
Version: e537193fc4a43b48ac51cc6366319e15e32dd540
Version: 6.14.6   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/block/ublk_drv.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "13456b4f1033d911f8bf3a0a1195656f293ba0f6",
              "status": "affected",
              "version": "e63d2228ef831af36f963b3ab8604160cfff84c1",
              "versionType": "git"
            },
            {
              "lessThan": "daa24603d9f0808929514ee62ced30052ca7221c",
              "status": "affected",
              "version": "e63d2228ef831af36f963b3ab8604160cfff84c1",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "e537193fc4a43b48ac51cc6366319e15e32dd540",
              "versionType": "git"
            },
            {
              "lessThan": "6.15",
              "status": "affected",
              "version": "6.14.6",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/block/ublk_drv.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.15"
            },
            {
              "lessThan": "6.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.19",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.3",
                  "versionStartIncluding": "6.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19",
                  "versionStartIncluding": "6.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "6.14.6",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nublk: clean up user copy references on ublk server exit\n\nIf a ublk server process releases a ublk char device file, any requests\ndispatched to the ublk server but not yet completed will retain a ref\nvalue of UBLK_REFCOUNT_INIT. Before commit e63d2228ef83 (\"ublk: simplify\naborting ublk request\"), __ublk_fail_req() would decrement the reference\ncount before completing the failed request. However, that commit\noptimized __ublk_fail_req() to call __ublk_complete_rq() directly\nwithout decrementing the request reference count.\nThe leaked reference count incorrectly allows user copy and zero copy\noperations on the completed ublk request. It also triggers the\nWARN_ON_ONCE(refcount_read(\u0026io-\u003eref)) warnings in ublk_queue_reinit()\nand ublk_deinit_queue().\nCommit c5c5eb24ed61 (\"ublk: avoid ublk_io_release() called after ublk\nchar dev is closed\") already fixed the issue for ublk devices using\nUBLK_F_SUPPORT_ZERO_COPY or UBLK_F_AUTO_BUF_REG. However, the reference\ncount leak also affects UBLK_F_USER_COPY, the other reference-counted\ndata copy mode. Fix the condition in ublk_check_and_reset_active_ref()\nto include all reference-counted data copy modes. This ensures that any\nublk requests still owned by the ublk server when it exits have their\nreference counts reset to 0."
        }
      ],
      "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 - Exploitation uses local close, io_uring, and pread/pwrite operations on a ublk character device; no network or physical path reaches the flaw.\nAC:L - A malicious server can control the outstanding I/O, server exit, request generation, and concurrent copy/commit operations. It can park the dispatch task or stall user copying, so the relevant race does not depend on uncontrollable conditions.\nPR:L - The data-plane open/read/write path has no capability check and explicitly supports non-CAP_SYS_ADMIN daemon tasks when device-node access is delegated. Device provisioning and recovery require initial-namespace CAP_SYS_ADMIN, but a low-privileged daemon account can exploit an already managed USER_COPY device.\nUI:N - The attacker can generate the necessary block I/O and server shutdown/recovery sequence without another user\u0027s action.\nS:U - The vulnerable ublk code and the affected kernel memory and execution context belong to the same kernel security authority.\nC:H - The stale reference can permit a copy before dispatch resets the refcount, after which concurrent completion can free or reuse bio, bvec, and request pages still being traversed. A pread operation can therefore disclose broadly controllable freed or reallocated kernel-backed memory.\nI:H - A concurrent pwrite can operate through freed or attacker-groomed bio/bvec state, providing a path to corrupt reused pages or redirect writes to kernel memory and potentially hijack control flow.\nA:H - The resulting use-after-free can cause an oops or kernel panic, and the deterministic WARN_ON_ONCE sites can also panic systems configured with panic-on-warn."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:11:51.227Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/13456b4f1033d911f8bf3a0a1195656f293ba0f6"
        },
        {
          "url": "https://git.kernel.org/stable/c/daa24603d9f0808929514ee62ced30052ca7221c"
        }
      ],
      "title": "ublk: clean up user copy references on ublk server exit",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-71070",
    "datePublished": "2026-01-13T15:31:24.709Z",
    "dateReserved": "2026-01-13T15:30:19.647Z",
    "dateUpdated": "2026-08-05T12:11:51.227Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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