CVE-2026-64070 (GCVE-0-2026-64070)
Vulnerability from cvelistv5
Published
2026-07-19 15:39
Modified
2026-09-02 12:49
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: powerpc/hv-gpci: fix preempt count leak in sysfs show paths Four sysfs show() callbacks in hv-gpci take get_cpu_var(hv_gpci_reqb) (which calls preempt_disable()) but only call the matching put_cpu_var() on the error path under the 'out:' label. Every successful read leaks one preempt_disable(): processor_bus_topology_show() processor_config_show() affinity_domain_via_virtual_processor_show() affinity_domain_via_domain_show() (affinity_domain_via_partition_show() was already correct.) On a CONFIG_PREEMPT=y kernel, repeated reads raise preempt_count and eventually return to userspace with preemption still disabled. The next user-mode page fault then hits faulthandler_disabled() == 1, gets forced to SIGSEGV, and the resulting coredump trips 'BUG: scheduling while atomic' in call_usermodehelper_exec -> wait_for_completion_state -> schedule: BUG: scheduling while atomic: <task>/<pid>/0x00000004 ... __schedule_bug+0x6c/0x90 __schedule+0x58c/0x13a0 schedule+0x48/0x1a0 schedule_timeout+0x104/0x170 wait_for_completion_state+0x16c/0x330 call_usermodehelper_exec+0x254/0x2d0 vfs_coredump+0x1050/0x2590 get_signal+0xb9c/0xc80 do_notify_resume+0xf8/0x470 Add an out_success label that calls put_cpu_var() before returning the byte count, mirroring affinity_domain_via_partition_show().
References
Impacted products
Vendor Product Version
Linux Linux Version: 71f1c39647d8c9d4d54a861ec81f1ff17544bcb6
Version: 71f1c39647d8c9d4d54a861ec81f1ff17544bcb6
Version: 71f1c39647d8c9d4d54a861ec81f1ff17544bcb6
Version: 71f1c39647d8c9d4d54a861ec81f1ff17544bcb6
Version: 71f1c39647d8c9d4d54a861ec81f1ff17544bcb6
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/powerpc/perf/hv-gpci.c"
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.6"
            },
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "version": "6.6.156",
              "versionType": "semver"
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              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.49",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.11",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
                },
                {
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                  "vulnerable": true
                },
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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\npowerpc/hv-gpci: fix preempt count leak in sysfs show paths\n\nFour sysfs show() callbacks in hv-gpci take get_cpu_var(hv_gpci_reqb)\n(which calls preempt_disable()) but only call the matching put_cpu_var()\non the error path under the \u0027out:\u0027 label. Every successful read leaks\none preempt_disable():\n\n  processor_bus_topology_show()\n  processor_config_show()\n  affinity_domain_via_virtual_processor_show()\n  affinity_domain_via_domain_show()\n\n(affinity_domain_via_partition_show() was already correct.)\n\nOn a CONFIG_PREEMPT=y kernel, repeated reads raise preempt_count and\neventually return to userspace with preemption still disabled. The\nnext user-mode page fault then hits faulthandler_disabled() == 1,\ngets forced to SIGSEGV, and the resulting coredump trips\n\u0027BUG: scheduling while atomic\u0027 in call_usermodehelper_exec -\u003e\nwait_for_completion_state -\u003e schedule:\n\n  BUG: scheduling while atomic: \u003ctask\u003e/\u003cpid\u003e/0x00000004\n  ...\n  __schedule_bug+0x6c/0x90\n  __schedule+0x58c/0x13a0\n  schedule+0x48/0x1a0\n  schedule_timeout+0x104/0x170\n  wait_for_completion_state+0x16c/0x330\n  call_usermodehelper_exec+0x254/0x2d0\n  vfs_coredump+0x1050/0x2590\n  get_signal+0xb9c/0xc80\n  do_notify_resume+0xf8/0x470\n\nAdd an out_success label that calls put_cpu_var() before returning\nthe byte count, mirroring affinity_domain_via_partition_show()."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-02T12:49:39.984Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/b300312562fd6e4729697adb9f777f00ca0429f3"
        },
        {
          "url": "https://git.kernel.org/stable/c/45afabe7f99c5d8746434ee41c86584c01d70147"
        },
        {
          "url": "https://git.kernel.org/stable/c/b61ebb2826ca1852c2bbd92a676fb622c358cab4"
        },
        {
          "url": "https://git.kernel.org/stable/c/903409000a07ac8e31ffedeb8516f4f8d67150c8"
        },
        {
          "url": "https://git.kernel.org/stable/c/dbc30a57bd8e026995e9fa8e8c31cffd18542c01"
        }
      ],
      "title": "powerpc/hv-gpci: fix preempt count leak in sysfs show paths",
      "x_generator": {
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  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64070",
    "datePublished": "2026-07-19T15:39:46.536Z",
    "dateReserved": "2026-07-19T07:54:57.030Z",
    "dateUpdated": "2026-09-02T12:49:39.984Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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