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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
VLAI
Title
powerpc/smp: do not decrement idle task preempt count in CPU offline
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.
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
References
Impacted products
Vendor Product Version CPE status
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)
guessed Create a notification for this product.
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)
guessed Create a notification for this product.
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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 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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-06-28T07:50:03+00:00",
      "cve": "CVE-2021-47454",
      "id": "CVE-2021-47454",
      "initial_release_date": "2021-01-01T00:00:00+00:00",
      "product_status:fixed": "280",
      "product_status:known_affected": "64",
      "product_status:known_not_affected": "56",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: powerpc/smp: do not decrement idle task preempt count in CPU offline",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-47454.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-11T16:58:24Z",
      "cve": "CVE-2021-47454",
      "id": "CVE-2021-47454",
      "initial_release_date": "2024-05-25T03:34:03Z",
      "product_status:known_affected": "275",
      "product_status:known_not_affected": "266",
      "product_status:recommended": "452",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2021-47454",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2021-47454.json",
      "version": "51"
    },
    "vulnrichment": {
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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.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.76\", \"versionStartIncluding\": \"5.10.50\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.14.15\", \"versionStartIncluding\": \"5.14\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15\", \"versionStartIncluding\": \"5.14\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionStartIncluding\": \"5.12.17\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionStartIncluding\": \"5.13.2\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": 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      "cveMetadata": "{\"cveId\": \"CVE-2021-47454\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-23T15:20:00.262Z\", \"dateReserved\": \"2024-05-21T14:58:30.833Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-05-22T06:19:44.040Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • 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.