CVE-2025-71070 (GCVE-0-2025-71070)

Vulnerability from cvelistv5 – Published: 2026-01-13 15:31 – Updated: 2026-02-09 08:34
VLAI?
Title
ublk: clean up user copy references on ublk server exit
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.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: e63d2228ef831af36f963b3ab8604160cfff84c1 , < 13456b4f1033d911f8bf3a0a1195656f293ba0f6 (git)
Affected: e63d2228ef831af36f963b3ab8604160cfff84c1 , < daa24603d9f0808929514ee62ced30052ca7221c (git)
Affected: e537193fc4a43b48ac51cc6366319e15e32dd540 (git)
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    Linux Linux Affected: 6.15
Unaffected: 0 , < 6.15 (semver)
Unaffected: 6.18.3 , ≤ 6.18.* (semver)
Unaffected: 6.19 , ≤ * (original_commit_for_fix)
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          "programFiles": [
            "drivers/block/ublk_drv.c"
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          "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."
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        "dateUpdated": "2026-02-09T08:34:20.822Z",
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          "url": "https://git.kernel.org/stable/c/13456b4f1033d911f8bf3a0a1195656f293ba0f6"
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          "url": "https://git.kernel.org/stable/c/daa24603d9f0808929514ee62ced30052ca7221c"
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      "title": "ublk: clean up user copy references on ublk server exit",
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    "cveId": "CVE-2025-71070",
    "datePublished": "2026-01-13T15:31:24.709Z",
    "dateReserved": "2026-01-13T15:30:19.647Z",
    "dateUpdated": "2026-02-09T08:34:20.822Z",
    "state": "PUBLISHED"
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