In the Linux kernel, the following vulnerability has been resolved:
iommu/amd: Fix pci device refcount leak in ppr_notifier()
As comment of pci_get_domain_bus_and_slot() says, it returns a pci device with refcount increment, when finish using it, the caller must decrement the reference count by calling pci_dev_put(). So call it before returning from ppr_notifier() to avoid refcount leak.