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CVE Record

CVE-2025-40163: sched/deadline: Stop dl_server before CPU goes offline

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]

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue can trigger a kernel warning during CPU removal operations. The provided sources describe an operational scheduler bug, not confirmed attacker exploitation. Business urgency depends on whether affected kernel versions are used on systems that perform CPU hotplug or CPU removal.

Executive priority

Treat as a targeted operational stability issue unless vendor guidance adds stronger impact detail. Patch during normal kernel maintenance, faster for platforms using CPU hotplug or CPU removal.

Technical view

The scheduler deadline server timer can fire after a CPU is removed from cpu_present_mask, reaching cpudl_set and triggering a warning. The fix stops dl_server before the CPU is marked dead. The source links only identify Linux kernel versions and stable commits, with no CVSS or CWE.

Likely exposure

Exposure appears limited to Linux systems running affected kernel versions, especially environments using CPU hotplug or CPU removal. The source example involved IBM CI and drmgr, but the CVE names Linux generally.

Exploitation context

The bundle does not show active exploitation, KEV listing, public exploit use, or attacker-controlled impact. The described trigger is a CPU removal operation that exposed a kernel scheduler timing bug.

Researcher notes

Evidence is incomplete for security impact: no CVSS, CWE, exploit status, or privilege boundary is provided. The root cause and fix direction are clear from the kernel description and stable commit references.

Mitigation direction

  • Apply a Linux kernel update containing the referenced stable fixes.
  • Check your distribution vendor advisory for backported patches.
  • Prioritize systems using CPU hotplug or planned CPU removal workflows.
  • Defer nonessential CPU removal operations on affected kernels where practical.

Validation and detection

  • Inventory Linux kernel versions against the CVE affected-version data.
  • Confirm distribution packages include one of the referenced stable fixes.
  • Review kernel logs for scheduler warnings during CPU removal events.
  • Validate remediation in a controlled maintenance or lab environment.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
4Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux030167dcadf50a9f9dac4de6fa4c34f4f7afeed7, 4ae8d9aa9f9dc7137ea5e564d79c5aa5af1bc45c, 4ae8d9aa9f9dc7137ea5e564d79c5aa5af1bc45cunaffected
LinuxLinux6.17, 0, 6.17.5, 6.18affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.