sched/deadline: Stop dl_server before CPU goes offline

{
  "id": "5698ea072cf3ab9305f59e0ad784ccc7d013e4dbd04a27c1445c0c757b3b6865",
  "url": "https://osv.dev/vulnerability/CVE-2025-40163",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "sched/deadline: Stop dl_server before CPU goes offline",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: sched/deadline: Stop dl_server before CPU goes offline IBM CI tool reported kernel warning[1] when running a CPU removal operation through drmgr[2]. i.e \"drmgr -c cpu -r -q 1\" WARNING: CPU: 0 PID: 0 at kernel/sched/cpudeadline.c:219 cpudl_set+0x58/0x170 NIP [c0000000002b6ed8] cpudl_set+0x58/0x170 LR [c0000000002b7cb8] dl_server_timer+0x168/0x2a0 Call Trace: [c000000002c2f8c0] init_stack+0x78c0/0x8000 (unreliable) [c0000000002b7cb8] dl_server_timer+0x168/0x2a0 [c00000000034df84] __hrtimer_run_queues+0x1a4/0x390 [c00000000034f624] hrtimer_interrupt+0x124/0x300 [c00000000002a230] timer_interrupt+0x140/0x320 Git bisects to: commit 4ae8d9aa9f9d (\"sched/deadline: Fix dl_server getting stuck\") This happens since: - dl_server hrtimer gets enqueued close to cpu offline, when kthread_park enqueues a fair task. - CPU goes offline and drmgr removes it from cpu_present_mask. - hrtimer fires and warning is hit. Fix it by stopping the dl_server before CPU is marked dead. [1]: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com/ [2]: https://github.com/ibm-power-utilities/powerpc-utils/tree/next/src/drmgr [sshegde: wrote the changelog and tested it]",
    "evidence": "osv:CVE-2025-40163",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
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        "prerequisites": [],
        "fixed_versions": [
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            "value": "6.17.5",
            "evidence": "/affected/1/ranges"
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    "severity": "unknown",
    "structured": {
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      "modified": "2026-10-28T02:30:51.039729625Z",
      "provider": "osv",
      "references": [
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        "https://git.kernel.org/stable/c/d7fd56ed5e07e053a5eea6112d61fcaded653b87",
        "https://git.kernel.org/stable/c/ee6e44dfe6e50b4a5df853d933a96bdff5309e6e",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/40xxx/CVE-2025-40163.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-40163",
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  "source_id": "core-osv",
  "document_id": 519895,
  "published_at": "2025-11-12T10:26:23.199+00:00"
}