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CVE Record

CVE-2021-46937: mm/damon/dbgfs: fix 'struct pid' leaks in 'dbgfs_target_ids_write()'

In the Linux kernel, the following vulnerability has been resolved: mm/damon/dbgfs: fix 'struct pid' leaks in 'dbgfs_target_ids_write()' DAMON debugfs interface increases the reference counts of 'struct pid's for targets from the 'target_ids' file write callback ('dbgfs_target_ids_write()'), but decreases the counts only in DAMON monitoring termination callback ('dbgfs_before_terminate()'). Therefore, when 'target_ids' file is repeatedly written without DAMON monitoring start/termination, the reference count is not decreased and therefore memory for the 'struct pid' cannot be freed. This commit fixes this issue by decreasing the reference counts when 'target_ids' is written.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysislow

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue can leak small kernel memory objects when the DAMON debugfs target list is rewritten repeatedly. Over time, that may contribute to resource exhaustion. The source does not show remote impact, privilege escalation, or active exploitation.

Executive priority

Treat as routine kernel maintenance unless sensitive multi-user systems expose DAMON debugfs. Prioritize affected shared hosts where untrusted local users may write debugfs controls.

Technical view

DAMON debugfs increments struct pid reference counts in dbgfs_target_ids_write() but previously released them only during monitoring termination. Repeated writes to target_ids without starting and terminating monitoring could leave references unreleased. The fix releases previous target references when target_ids is written.

Likely exposure

Exposure appears limited to Linux systems running affected kernel versions with DAMON debugfs available and writable. Practical risk depends on local access controls, debugfs mounting, and distro backports.

Exploitation context

The bundle reports no KEV listing and provides no cited evidence of active exploitation. The described condition requires repeated writes to a DAMON debugfs control file, suggesting local operational or insider abuse rather than internet-facing exposure.

Researcher notes

The evidence supports a reference-count leak causing kernel memory not to be freed. The source does not provide CVSS, CWE, exploit status, or a complete distro-specific affected matrix, so validation should rely on kernel commit ancestry and vendor backports.

Mitigation direction

  • Apply vendor or distro kernel updates containing the referenced stable fixes.
  • Check Linux vendor advisories for exact package versions and backports.
  • Restrict access to debugfs and DAMON controls to trusted administrators.
  • Disable or avoid mounting debugfs where it is not operationally required.

Validation and detection

  • Inventory hosts running Linux kernels in the affected 5.15-era range.
  • Confirm whether debugfs and DAMON debugfs interfaces are enabled.
  • Verify installed kernel packages include the referenced stable fix commits or distro backports.
  • Review local permissions for writes to DAMON target_ids controls.
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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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
2ADP providers
3Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

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

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ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux4bc05954d0076655cfaf6f0135585bdc20cd6b11, 4bc05954d0076655cfaf6f0135585bdc20cd6b11unaffected
LinuxLinux5.15, 0, 5.15.13, 5.16affected
Weakness

CWE details

No CWE listed

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