CVE-2021-47327

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.