CVE-2021-47454

{"id": "CVE-2021-47454", "cveTags": [], "metrics": {"cvssMetricV31": [{"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 5.5, "attackVector": "LOCAL", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 1.8}]}, "published": "2024-05-22T07:15:10.453", "references": [{"url": "https://git.kernel.org/stable/c/3ea0b497a7a2fff6a4b7090310c9f52c91975934", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/53770a411559cf7bc0906d1df319cc533d2f4f58", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/787252a10d9422f3058df9a4821f389e5326c440", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/3ea0b497a7a2fff6a4b7090310c9f52c91975934", "tags": ["Patch"], "source": "af854a3a-2127-422b-91ae-364da2661108"}, {"url": "https://git.kernel.org/stable/c/53770a411559cf7bc0906d1df319cc533d2f4f58", "tags": ["Patch"], "source": "af854a3a-2127-422b-91ae-364da2661108"}, {"url": "https://git.kernel.org/stable/c/787252a10d9422f3058df9a4821f389e5326c440", "tags": ["Patch"], "source": "af854a3a-2127-422b-91ae-364da2661108"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Primary", "source": "nvd@nist.gov", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "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's arch_cpu_idle_dead() decrements the idle task's\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't touch the idle\ntask's 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't 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."}], "lastModified": "2025-09-29T16:48:58.817", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "54D73BB5-05A6-4980-BAB3-2AAAEFB143AC", "versionEndExcluding": "5.10.76", "versionStartIncluding": "5.10.50"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "CDB1D52E-21AB-4ECE-9119-6594F8FF3B3A", "versionEndExcluding": "5.13", "versionStartIncluding": "5.12.17"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "F839A199-75DE-4660-A33E-5921B73B1FF6", "versionEndExcluding": "5.14.15", "versionStartIncluding": "5.13.2"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.15:rc1:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "E46C74C6-B76B-4C94-A6A4-FD2FFF62D644"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.15:rc2:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "60134C3A-06E4-48C1-B04F-2903732A4E56"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.15:rc3:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "0460DA88-8FE1-46A2-9DDA-1F1ABA552E71"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.15:rc4:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "AF55383D-4DF2-45DC-93F7-571F4F978EAB"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.15:rc5:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "9E9481B2-8AA6-4CBD-B5D3-C10F51FF6D01"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.15:rc6:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "EBD45831-4B79-42BC-ABC0-86870F0DEA89"}], "operator": "OR"}]}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}