cve-2021-47454
Vulnerability from cvelistv5
Published
2024-05-22 06:19
Modified
2024-08-04 05:39
Severity
Summary
powerpc/smp: do not decrement idle task preempt count in CPU offline
References
SourceURLTags
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3ea0b497a7a2fff6a4b7090310c9f52c91975934
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/53770a411559cf7bc0906d1df319cc533d2f4f58
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/787252a10d9422f3058df9a4821f389e5326c440
Impacted products
VendorProduct
LinuxLinux
LinuxLinux
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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."
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    "cveId": "CVE-2021-47454",
    "datePublished": "2024-05-22T06:19:44.040Z",
    "dateReserved": "2024-05-21T14:58:30.833Z",
    "dateUpdated": "2024-08-04T05:39:59.627Z",
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    "nvd": "{\"cve\":{\"id\":\"CVE-2021-47454\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2024-05-22T07:15:10.453\",\"lastModified\":\"2024-05-22T12:46:53.887\",\"vulnStatus\":\"Awaiting Analysis\",\"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.\"},{\"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.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/3ea0b497a7a2fff6a4b7090310c9f52c91975934\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/53770a411559cf7bc0906d1df319cc533d2f4f58\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/787252a10d9422f3058df9a4821f389e5326c440\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
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