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CVE Record

CVE-2025-38522: sched/ext: Prevent update_locked_rq() calls with NULL rq

In the Linux kernel, the following vulnerability has been resolved: sched/ext: Prevent update_locked_rq() calls with NULL rq Avoid invoking update_locked_rq() when the runqueue (rq) pointer is NULL in the SCX_CALL_OP and SCX_CALL_OP_RET macros. Previously, calling update_locked_rq(NULL) with preemption enabled could trigger the following warning: BUG: using __this_cpu_write() in preemptible [00000000] This happens because __this_cpu_write() is unsafe to use in preemptible context. rq is NULL when an ops invoked from an unlocked context. In such cases, we don't need to store any rq, since the value should already be NULL (unlocked). Ensure that update_locked_rq() is only called when rq is non-NULL, preventing calling __this_cpu_write() on preemptible context.

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 an unsafe per-CPU write path when scheduler extension code is called without a runqueue. The public record describes a kernel warning rather than a confirmed compromise path. No CVSS score, CWE, or active exploitation evidence is provided.

Executive priority

Handle through normal kernel patch governance, with higher priority for systems using sched_ext or rapidly tracking mainline kernels. The current evidence does not support emergency treatment, but the affected component is kernel-level.

Technical view

The fix prevents SCX_CALL_OP and SCX_CALL_OP_RET from calling update_locked_rq() when rq is NULL. The NULL rq case occurs for ops invoked from an unlocked context. Calling update_locked_rq(NULL) with preemption enabled can reach __this_cpu_write(), which is unsafe in preemptible context.

Likely exposure

Exposure is limited to Linux systems running affected kernel builds listed in the source bundle, especially around 6.15, 6.15.8, and 6.16 entries. Distribution backports may change status, so package-level vendor mapping is required.

Exploitation context

The bundle does not cite exploitation in the wild, and KEV status is false. The described behavior is a kernel warning path tied to sched/ext internals; no public source here establishes attacker control, privilege impact, or exploitability.

Researcher notes

Key evidence is narrow: a NULL rq guard in sched/ext macro paths prevents update_locked_rq(NULL) in preemptible context. Missing CVSS, CWE, exploitability analysis, and distro-specific affected ranges limit risk precision.

Mitigation direction

  • Apply a vendor kernel update containing the referenced stable fixes.
  • Check distribution advisories for backported fix status.
  • Prioritize hosts using or testing Linux scheduler extensions.
  • If patching is delayed, follow vendor guidance; no source-named workaround is provided.

Validation and detection

  • Inventory Linux kernel versions across affected fleets.
  • Identify systems where sched_ext is enabled, tested, or operationally relevant.
  • Compare kernel package changelogs against the referenced stable commits.
  • Review kernel logs for the cited preemptible __this_cpu_write warning.
  • Confirm patched kernels in staging before production rollout.
Prepared
Confidence
medium
Sources
4

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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CVE-2025-38522 mapping review

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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
3Source 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
LinuxLinux18853ba782bef65fc81ef2b3370382e5b479c5eb, 18853ba782bef65fc81ef2b3370382e5b479c5ebunaffected
LinuxLinux6.15, 0, 6.15.8, 6.16affected
Weakness

CWE details

No CWE listed

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