Hi!
From: Xiyu Yang xiyuyang19@fudan.edu.cn
[ Upstream commit 1adf30f198c26539a62d761e45af72cde570413d ]
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.
Yes.
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.
Yes, some error paths do that. But some callers (arm_smmu_map, arm_smmu_unmap, arm_smmu_flush_iotlb_all, ...) ignore return value of arm_smmu_rpm_get().
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.
So no, this is not fixed; it is just unbalanced in the other (more dangerous) direction now.
Best regards, Pavel