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CVE Record

CVE-2021-47305: dma-buf/sync_file: Don't leak fences on merge failure

In the Linux kernel, the following vulnerability has been resolved: dma-buf/sync_file: Don't leak fences on merge failure Each add_fence() call does a dma_fence_get() on the relevant fence. In the error path, we weren't calling dma_fence_put() so all those fences got leaked. Also, in the krealloc_array failure case, we weren't freeing the fences array. Instead, ensure that i and fences are always zero-initialized and dma_fence_put() all the fences and kfree(fences) on every error path.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-47305 is a Linux kernel resource-leak bug in dma-buf sync file fence merging. When a merge failed, the kernel could retain fence references and an array instead of releasing them. The public record does not provide CVSS, CWE, exploitability details, or confirmed business impact.

Executive priority

Treat this as a kernel hygiene issue with incomplete severity data. It does not justify emergency response based on the provided sources alone, but affected kernels should be brought into normal security patch cycles.

Technical view

The flaw is in dma-buf/sync_file error handling. add_fence() increments fence references with dma_fence_get(), but merge-failure paths did not consistently call dma_fence_put(); one krealloc_array failure path also missed kfree(fences). Stable commits add cleanup on every error path.

Likely exposure

Exposure is limited to Linux systems running affected kernel code paths. The bundle lists Linux kernel affected versions and stable commit references, but not distribution package mappings, enabled subsystems, or reachable attack surfaces.

Exploitation context

No active exploitation is stated in the source bundle, and KEV is false. The provided material describes a resource leak on failure paths, not a public exploit, privilege boundary, or remote attack scenario.

Researcher notes

The useful evidence is the upstream fix rationale: missing dma_fence_put() and kfree(fences) on merge error paths. The bundle lacks CVSS, CWE, proof-of-concept status, distribution advisories, or details proving local or remote exploitability.

Mitigation direction

  • Check Linux vendor advisories for patched kernels containing the referenced stable commits.
  • Prioritize kernel updates where untrusted users or workloads can reach graphics or dma-buf functionality.
  • Track distribution-specific package versions rather than upstream commit hashes alone.
  • If patch timing is unclear, ask the OS vendor for exposure guidance.

Validation and detection

  • Inventory Linux kernel versions across servers, endpoints, containers, and appliances.
  • Map each kernel package to vendor advisories or the referenced upstream stable commits.
  • Confirm whether dma-buf/sync_file functionality is present and relevant on affected systems.
  • Document systems where kernel updates cannot be applied promptly.
Prepared
Confidence
medium
Sources
8

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2021-47305 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
2ADP providers
7Source 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

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

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
LinuxLinuxa02b9dc90d844cc7df7b63264e7920cc425052d9, a02b9dc90d844cc7df7b63264e7920cc425052d9, a02b9dc90d844cc7df7b63264e7920cc425052d9, a02b9dc90d844cc7df7b63264e7920cc425052d9, a02b9dc90d844cc7df7b63264e7920cc425052d9, a02b9dc90d844cc7df7b63264e7920cc425052d9unaffected
LinuxLinux4.9, 0, 4.14.241, 4.19.199, 5.4.135, 5.10.53, 5.13.5, 5.14affected
Weakness

CWE details

No CWE listed

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