{
    "data_version": "4.0",
    "data_type": "CVE",
    "data_format": "MITRE",
    "CVE_data_meta": {
        "ID": "CVE-2021-47454",
        "ASSIGNER": "cve@kernel.org",
        "STATE": "PUBLIC"
    },
    "description": {
        "description_data": [
            {
                "lang": "eng",
                "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."
            }
        ]
    },
    "problemtype": {
        "problemtype_data": [
            {
                "description": [
                    {
                        "lang": "eng",
                        "value": "n/a"
                    }
                ]
            }
        ]
    },
    "affects": {
        "vendor": {
            "vendor_data": [
                {
                    "vendor_name": "Linux",
                    "product": {
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                            {
                                "product_name": "Linux",
                                "version": {
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                                            "version_name": "bdf4d33e8342",
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                                        {
                                            "version_affected": "<",
                                            "version_name": "2c669ef6979c",
                                            "version_value": "3ea0b497a7a2"
                                        },
                                        {
                                            "version_value": "not down converted",
                                            "x_cve_json_5_version_data": {
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                                                    {
                                                        "version": "5.14",
                                                        "status": "affected"
                                                    },
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                                                        "version": "0",
                                                        "lessThan": "5.14",
                                                        "status": "unaffected",
                                                        "versionType": "custom"
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                                                    {
                                                        "version": "5.10.76",
                                                        "lessThanOrEqual": "5.10.*",
                                                        "status": "unaffected",
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                                                    {
                                                        "version": "5.14.15",
                                                        "lessThanOrEqual": "5.14.*",
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                                                        "versionType": "custom"
                                                    },
                                                    {
                                                        "version": "5.15",
                                                        "lessThanOrEqual": "*",
                                                        "status": "unaffected",
                                                        "versionType": "original_commit_for_fix"
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    "references": {
        "reference_data": [
            {
                "url": "https://git.kernel.org/stable/c/53770a411559cf7bc0906d1df319cc533d2f4f58",
                "refsource": "MISC",
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                "name": "https://git.kernel.org/stable/c/3ea0b497a7a2fff6a4b7090310c9f52c91975934"
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