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CVE Record

CVE-2024-56706: s390/cpum_sf: Fix and protect memory allocation of SDBs with mutex

In the Linux kernel, the following vulnerability has been resolved: s390/cpum_sf: Fix and protect memory allocation of SDBs with mutex Reservation of the PMU hardware is done at first event creation and is protected by a pair of mutex_lock() and mutex_unlock(). After reservation of the PMU hardware the memory required for the PMUs the event is to be installed on is allocated by allocate_buffers() and alloc_sampling_buffer(). This done outside of the mutex protection. Without mutex protection two or more concurrent invocations of perf_event_init() may run in parallel. This can lead to allocation of Sample Data Blocks (SDBs) multiple times for the same PMU. Prevent this and protect memory allocation of SDBs by mutex.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A race condition in the Linux kernel’s IBM Z (s390) performance-monitoring code can allocate sampling memory more than once for the same hardware unit. A local, low-privileged user may be able to trigger serious confidentiality, integrity, or availability consequences. Exposure appears limited to affected s390 systems using this performance-monitoring path.

Executive priority

Prioritize prompt assessment of s390 Linux systems, especially shared hosts or systems running untrusted workloads. Patch confirmed affected systems through supported distribution channels. Other architectures are not identified as affected by the supplied evidence. Escalate if local users can access performance monitoring or if kernel provenance cannot be verified.

Technical view

Concurrent perf_event_init() calls can reach allocate_buffers() and alloc_sampling_buffer() outside the PMU reservation mutex. This permits duplicate Sample Data Block allocations for one PMU. The correction extends mutex protection around SDB allocation. The supplied CVSS 3.1 score is 7.8: local access, low complexity, low privileges, no user interaction, and high C/I/A impact.

Likely exposure

Likely exposure is limited to Linux on s390 where the cpum_sf PMU sampling facility is present and accessible to local users. The bundle identifies Linux 6.12-related versions and a 6.13 boundary, but its version data is ambiguous. Confirm exact exposure against the CVE record, distribution advisories, and installed kernel provenance.

Exploitation context

The weakness requires local access and low privileges according to the supplied CVSS vector. Triggering involves concurrent performance-event initialization. The bundle marks the CVE as absent from KEV and provides no cited evidence of active exploitation or a public exploit. Exploitability under specific distribution security settings is not established.

Researcher notes

The reported flaw is a mutex coverage error in s390/cpum_sf SDB allocation, not PMU reservation itself. Duplicate allocation for a single PMU is the described failure condition. The bundle provides fix commits but no crash trace, exploit evidence, affected-distribution mapping, or precise consequences connecting the race to each rated C/I/A impact.

Mitigation direction

  • Install a vendor-supported kernel containing the referenced mutex-protection fix.
  • Check distribution advisories for exact fixed package versions and reboot requirements.
  • Restrict unnecessary local access and performance-monitoring privileges until patched.
  • Prioritize affected multi-user or untrusted-workload s390 systems.

Validation and detection

  • Confirm each host uses the s390 architecture and identify its exact kernel build.
  • Compare kernel provenance with the CVE record, stable commits, and distribution advisories.
  • Verify the installed kernel incorporates one of the referenced fixes or its backport.
  • Confirm patched systems booted into the updated kernel after maintenance.
  • Review local perf access controls and exposure to untrusted users.
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-2024-56706 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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.

1CVSS vectors
3Timeline events
0ADP providers
3Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2024-56706Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

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
LinuxLinux8a6fe8f21ec4f049a7b1fe120ad50a5065a9c7a8, 8a6fe8f21ec4f049a7b1fe120ad50a5065a9c7a8unaffected
LinuxLinux6.12, 0, 6.12.2, 6.13affected
Weakness

CWE details

No CWE listed

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