CVE-2025-38584 (GCVE-0-2025-38584)
Vulnerability from cvelistv5
Published
2025-08-19 17:03
Modified
2026-08-05 12:03
Severity ?
7.0 (High) - CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: padata: Fix pd UAF once and for all There is a race condition/UAF in padata_reorder that goes back to the initial commit. A reference count is taken at the start of the process in padata_do_parallel, and released at the end in padata_serial_worker. This reference count is (and only is) required for padata_replace to function correctly. If padata_replace is never called then there is no issue. In the function padata_reorder which serves as the core of padata, as soon as padata is added to queue->serial.list, and the associated spin lock released, that padata may be processed and the reference count on pd would go away. Fix this by getting the next padata before the squeue->serial lock is released. In order to make this possible, simplify padata_reorder by only calling it once the next padata arrives.
References
Impacted products
Vendor Product Version
Linux Linux Version: 16295bec6398a3eedc9377e1af6ff4c71b98c300
Version: 16295bec6398a3eedc9377e1af6ff4c71b98c300
Version: 16295bec6398a3eedc9377e1af6ff4c71b98c300
Version: 16295bec6398a3eedc9377e1af6ff4c71b98c300
Version: 16295bec6398a3eedc9377e1af6ff4c71b98c300
Version: 16295bec6398a3eedc9377e1af6ff4c71b98c300
Version: 16295bec6398a3eedc9377e1af6ff4c71b98c300
Version: 16295bec6398a3eedc9377e1af6ff4c71b98c300
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{
  "containers": {
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/linux/padata.h",
            "kernel/padata.c"
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      ],
      "cpeApplicability": [
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npadata: Fix pd UAF once and for all\n\nThere is a race condition/UAF in padata_reorder that goes back\nto the initial commit.  A reference count is taken at the start\nof the process in padata_do_parallel, and released at the end in\npadata_serial_worker.\n\nThis reference count is (and only is) required for padata_replace\nto function correctly.  If padata_replace is never called then\nthere is no issue.\n\nIn the function padata_reorder which serves as the core of padata,\nas soon as padata is added to queue-\u003eserial.list, and the associated\nspin lock released, that padata may be processed and the reference\ncount on pd would go away.\n\nFix this by getting the next padata before the squeue-\u003eserial lock\nis released.\n\nIn order to make this possible, simplify padata_reorder by only\ncalling it once the next padata arrives."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerable padata reorder path is only driven by pcrypt AEAD requests, which an unprivileged local user submits via AF_ALG sockets (or in-kernel IPsec); the required `padata_replace()`/`padata_free_shell()` side is a local sysfs/CPU-hotplug/netlink action, so a purely remote attacker cannot set up the necessary state.\nAC:H - The attacker controls only one side of the race (the pcrypt request stream); dropping the base `pd` reference requires `padata_replace()` via root-only sysfs cpumask writes, CPU hotplug, or init-ns CAP_NET_ADMIN `crypto_del_alg` \u2014 conditions truly outside an unprivileged attacker\u0027s control, and the window between `spin_unlock(\u0026squeue-\u003eserial.lock)` and the next `pd` dereference must coincide with the final refcount drop.\nPR:L - An unprivileged user with no capabilities can open AF_ALG sockets and flood `pcrypt(...)` requests to drive `padata_do_parallel`/`padata_do_serial` and hold the race open; no capability check exists on that path.\nUI:N - No victim action is needed \u2014 the `padata_replace()` trigger routinely occurs automatically via CPU hotplug (cloud vCPU resize, thermal/power hotplug on embedded and Android, suspend/resume offlining secondary CPUs) rather than through a human interacting with content.\nS:U - The use-after-free is on a kernel slab/percpu object and its consequences stay within the kernel\u0027s own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The freed `struct parallel_data` and its freed percpu `reorder_list`/`squeue` are read after free (`pd-\u003ecpu`, `pd-\u003eprocessed`, `reorder-\u003elock`, list pointers), and reclaiming those allocations with attacker-sprayed objects turns the UAF into an arbitrary kernel-memory read primitive.\nI:H - After the free, `padata_reorder()` writes into the freed object (`spin_unlock_bh(\u0026pd-\u003elock)`, `refcount_inc()`, `list_del_init()`) and queues `\u0026pd-\u003ereorder_work` and `\u0026squeue-\u003ework` \u2014 work_structs inside freed memory whose `func` pointer is later invoked, giving control-flow hijack and privilege escalation once the slab is reclaimed.\nA:H - Even unexploited, the use-after-free corrupts freed slab and percpu memory, takes a spinlock in freed storage, and queues a work item with a stale function pointer, reliably producing a kernel oops/panic."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:03:10.424Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a2048e475e22b13dc3e53d485b7e6e11464ed9a6"
        },
        {
          "url": "https://git.kernel.org/stable/c/73f132e60857038416540c3599b1de6033d7575a"
        },
        {
          "url": "https://git.kernel.org/stable/c/609e59193fc6d9dd323f1c6ae1fdd721f1c79680"
        },
        {
          "url": "https://git.kernel.org/stable/c/a11a12a9880ab37342b73c93cfe1a3ada02ff0db"
        },
        {
          "url": "https://git.kernel.org/stable/c/f231d5d001ec75f5886c02d496a4c79edc383d45"
        },
        {
          "url": "https://git.kernel.org/stable/c/dbe3e911a59bda6de96e7cae387ff882c2c177fa"
        },
        {
          "url": "https://git.kernel.org/stable/c/cdf79bd2e1ecb3cc75631c73d8f4149be6019a52"
        },
        {
          "url": "https://git.kernel.org/stable/c/71203f68c7749609d7fc8ae6ad054bdedeb24f91"
        }
      ],
      "title": "padata: Fix pd UAF once and for all",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-38584",
    "datePublished": "2025-08-19T17:03:06.172Z",
    "dateReserved": "2025-04-16T04:51:24.026Z",
    "dateUpdated": "2026-08-05T12:03:10.424Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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