Description
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]
Published: 2025-11-12
Score: 5.5 Medium
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
Ubuntu USN Ubuntu USN USN-8029-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8030-1 Linux kernel (GCP) vulnerabilities
Ubuntu USN Ubuntu USN USN-8029-2 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8048-1 Linux kernel (OEM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8029-3 Linux kernel (Azure) vulnerabilities
History

Mon, 01 Dec 2025 06:30:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

Fri, 14 Nov 2025 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate


Wed, 12 Nov 2025 23:00:00 +0000

Type Values Removed Values Added
First Time appeared Linux
Linux linux Kernel
Vendors & Products Linux
Linux linux Kernel

Wed, 12 Nov 2025 10:30:00 +0000

Type Values Removed Values Added
Description 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]
Title sched/deadline: Stop dl_server before CPU goes offline
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-05-11T21:43:57.690Z

Reserved: 2025-04-16T07:20:57.176Z

Link: CVE-2025-40163

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Deferred

Published: 2025-11-12T11:15:46.517

Modified: 2026-04-15T00:35:42.020

Link: CVE-2025-40163

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-11-12T00:00:00Z

Links: CVE-2025-40163 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2025-11-12T22:12:14Z

Weaknesses

No weakness.