CVE-2021-47327: iommu/arm-smmu: Fix arm_smmu_device refcount leak when arm_smmu_rpm_get fails

Severity: high (CVSS 7.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-05-21 · updated 2026-06-17
Weakness: CWE-911

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.

Affected products

Linux kernel: before 5.4.134; from 5.5 before 5.10.52; from 5.11 before 5.12.19; from 5.13 before 5.13.4 — fixed in 5.10.52, 5.12.19, 5.13.4, 5.4.134

How to fix

Upgrade to a fixed version: Linux kernel 5.10.52, 5.12.19, 5.13.4, 5.4.134. Check the vendor advisory for mitigations.

References

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