Vulnerability-Lookup

FKIE_CVE-2021-47454

Vulnerability from fkie_nvd - Published: 2024-05-22 07:15 - Updated: 2026-06-17 04:17

Severity

5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Summary

In the Linux kernel, the following vulnerability has been resolved: powerpc/smp: do not decrement idle task preempt count in CPU offline With PREEMPT_COUNT=y, when a CPU is offlined and then onlined again, we get: BUG: scheduling while atomic: swapper/1/0/0x00000000 no locks held by swapper/1/0. CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.15.0-rc2+ #100 Call Trace: dump_stack_lvl+0xac/0x108 __schedule_bug+0xac/0xe0 __schedule+0xcf8/0x10d0 schedule_idle+0x3c/0x70 do_idle+0x2d8/0x4a0 cpu_startup_entry+0x38/0x40 start_secondary+0x2ec/0x3a0 start_secondary_prolog+0x10/0x14 This is because powerpc's arch_cpu_idle_dead() decrements the idle task's preempt count, for reasons explained in commit a7c2bb8279d2 ("powerpc: Re-enable preemption before cpu_die()"), specifically "start_secondary() expects a preempt_count() of 0." However, since commit 2c669ef6979c ("powerpc/preempt: Don't touch the idle task's preempt_count during hotplug") and commit f1a0a376ca0c ("sched/core: Initialize the idle task with preemption disabled"), that justification no longer holds. The idle task isn't supposed to re-enable preemption, so remove the vestigial preempt_enable() from the CPU offline path. Tested with pseries and powernv in qemu, and pseries on PowerVM.

References

URL	Tags
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/3ea0b497a7a2fff6a4b7090310c9f52c91975934	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/53770a411559cf7bc0906d1df319cc533d2f4f58	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/787252a10d9422f3058df9a4821f389e5326c440	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/3ea0b497a7a2fff6a4b7090310c9f52c91975934	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/53770a411559cf7bc0906d1df319cc533d2f4f58	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/787252a10d9422f3058df9a4821f389e5326c440	Patch

Impacted products

Vendor	Product	Version
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	5.15
linux	linux_kernel	5.15
linux	linux_kernel	5.15
linux	linux_kernel	5.15
linux	linux_kernel	5.15
linux	linux_kernel	5.15

JSON

To clipboard

{
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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npowerpc/smp: do not decrement idle task preempt count in CPU offline\n\nWith PREEMPT_COUNT=y, when a CPU is offlined and then onlined again, we\nget:\n\nBUG: scheduling while atomic: swapper/1/0/0x00000000\nno locks held by swapper/1/0.\nCPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.15.0-rc2+ #100\nCall Trace:\n dump_stack_lvl+0xac/0x108\n __schedule_bug+0xac/0xe0\n __schedule+0xcf8/0x10d0\n schedule_idle+0x3c/0x70\n do_idle+0x2d8/0x4a0\n cpu_startup_entry+0x38/0x40\n start_secondary+0x2ec/0x3a0\n start_secondary_prolog+0x10/0x14\n\nThis is because powerpc\u0027s arch_cpu_idle_dead() decrements the idle task\u0027s\npreempt count, for reasons explained in commit a7c2bb8279d2 (\"powerpc:\nRe-enable preemption before cpu_die()\"), specifically \"start_secondary()\nexpects a preempt_count() of 0.\"\n\nHowever, since commit 2c669ef6979c (\"powerpc/preempt: Don\u0027t touch the idle\ntask\u0027s preempt_count during hotplug\") and commit f1a0a376ca0c (\"sched/core:\nInitialize the idle task with preemption disabled\"), that justification no\nlonger holds.\n\nThe idle task isn\u0027t supposed to re-enable preemption, so remove the\nvestigial preempt_enable() from the CPU offline path.\n\nTested with pseries and powernv in qemu, and pseries on PowerVM."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: powerpc/smp: no disminuye el recuento de prioridad de tareas inactivas en la CPU fuera de l\u00ednea Con PREEMPT_COUNT=y, cuando una CPU est\u00e1 fuera de l\u00ednea y luego vuelve a estar en l\u00ednea, obtenemos: ERROR: programaci\u00f3n mientras es at\u00f3mica: swapper/1/0/0x00000000 no hay bloqueos retenidos por swapper/1/0. CPU: 1 PID: 0 Comunicaciones: swapper/1 No contaminado 5.15.0-rc2+ #100 Seguimiento de llamadas: dump_stack_lvl+0xac/0x108 __schedule_bug+0xac/0xe0 __schedule+0xcf8/0x10d0 Schedule_idle+0x3c/0x70 do_idle+0x2d8/0x4a0 entrada_arriba+ 0x38/0x40 start_secondary+0x2ec/0x3a0 start_secondary_prolog+0x10/0x14 Esto se debe a que arch_cpu_idle_dead() de powerpc disminuye el recuento de apropiaci\u00f3n de tareas inactivas, por razones explicadas en el commit a7c2bb8279d2 (\"powerpc: volver a habilitar la apropiaci\u00f3n antes de cpu_die()\"), espec\u00edficamente \" start_secondary() espera un preempt_count() de 0.\" Sin embargo, desde el commit 2c669ef6979c (\"powerpc/preempt: no toque el preempt_count de la tarea inactiva durante la conexi\u00f3n en caliente\") y el commit f1a0a376ca0c (\"sched/core: inicialice la tarea inactiva con la preferencia deshabilitada\"), esa justificaci\u00f3n ya no se cumple. No se supone que la tarea inactiva vuelva a habilitar la preferencia, por lo tanto, elimine el preempt_enable() residual de la ruta fuera de l\u00ednea de la CPU. Probado con pseries y powernv en qemu y pseries en PowerVM."
    }
  ],
  "id": "CVE-2021-47454",
  "lastModified": "2026-06-17T04:17:30.660",
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          "baseScore": 5.5,
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          "confidentialityImpact": "NONE",
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CVE-2021-47454 (GCVE-0-2021-47454)

Vulnerability from cvelistv5 – Published: 2024-05-22 06:19 – Updated: 2026-05-23 15:20

Title

powerpc/smp: do not decrement idle task preempt count in CPU offline

Summary

Severity

No CVSS data available.

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2024-05-22 19:49 UTC

Assigner

Linux mitre root

References

3 references

URL	Tags
https://git.kernel.org/stable/c/53770a411559cf7bc…
https://git.kernel.org/stable/c/3ea0b497a7a2fff6a…
https://git.kernel.org/stable/c/787252a10d9422f30…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: bdf4d33e8342b90386156204e1da0cdfdb4bf146 , < 53770a411559cf7bc0906d1df319cc533d2f4f58 (git) Affected: 2c669ef6979c370f98d4b876e54f19613c81e075 , < 3ea0b497a7a2fff6a4b7090310c9f52c91975934 (git) Affected: 2c669ef6979c370f98d4b876e54f19613c81e075 , < 787252a10d9422f3058df9a4821f389e5326c440 (git) Affected: 2b6148ef2bd6d8ddc76e7873114f7769b6aa25f0 (git) Affected: 20a015e948b825afb47855de2efce7cae7c2608f (git) Affected: 5.10.50 , < 5.10.76 (semver) Affected: 5.12.17 , < 5.13 (semver) Affected: 5.13.2 , < 5.14 (semver)
Linux	Linux	Affected: 5.14 Unaffected: 0 , < 5.14 (semver) Unaffected: 5.10.76 , ≤ 5.10.* (semver) Unaffected: 5.14.15 , ≤ 5.14.* (semver) Unaffected: 5.15 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npowerpc/smp: do not decrement idle task preempt count in CPU offline\n\nWith PREEMPT_COUNT=y, when a CPU is offlined and then onlined again, we\nget:\n\nBUG: scheduling while atomic: swapper/1/0/0x00000000\nno locks held by swapper/1/0.\nCPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.15.0-rc2+ #100\nCall Trace:\n dump_stack_lvl+0xac/0x108\n __schedule_bug+0xac/0xe0\n __schedule+0xcf8/0x10d0\n schedule_idle+0x3c/0x70\n do_idle+0x2d8/0x4a0\n cpu_startup_entry+0x38/0x40\n start_secondary+0x2ec/0x3a0\n start_secondary_prolog+0x10/0x14\n\nThis is because powerpc\u0027s arch_cpu_idle_dead() decrements the idle task\u0027s\npreempt count, for reasons explained in commit a7c2bb8279d2 (\"powerpc:\nRe-enable preemption before cpu_die()\"), specifically \"start_secondary()\nexpects a preempt_count() of 0.\"\n\nHowever, since commit 2c669ef6979c (\"powerpc/preempt: Don\u0027t touch the idle\ntask\u0027s preempt_count during hotplug\") and commit f1a0a376ca0c (\"sched/core:\nInitialize the idle task with preemption disabled\"), that justification no\nlonger holds.\n\nThe idle task isn\u0027t supposed to re-enable preemption, so remove the\nvestigial preempt_enable() from the CPU offline path.\n\nTested with pseries and powernv in qemu, and pseries on PowerVM."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-23T15:20:00.262Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/53770a411559cf7bc0906d1df319cc533d2f4f58"
        },
        {
          "url": "https://git.kernel.org/stable/c/3ea0b497a7a2fff6a4b7090310c9f52c91975934"
        },
        {
          "url": "https://git.kernel.org/stable/c/787252a10d9422f3058df9a4821f389e5326c440"
        }
      ],
      "title": "powerpc/smp: do not decrement idle task preempt count in CPU offline",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2021-47454",
    "datePublished": "2024-05-22T06:19:44.040Z",
    "dateReserved": "2024-05-21T14:58:30.833Z",
    "dateUpdated": "2026-05-23T15:20:00.262Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.