PCI: endpoint: Fix PCI domain ID release in pci_epc_destroy()

pci_epc_destroy() invokes pci_bus_release_domain_nr() to release the PCI
domain ID, but there are two issues:

  - 'epc->dev' is passed to pci_bus_release_domain_nr() which was already
    freed by device_unregister(), leading to a use-after-free issue.

  - Domain ID corresponds to the EPC device parent, so passing 'epc->dev'
    is also wrong.

Fix these issues by passing 'epc->dev.parent' to
pci_bus_release_domain_nr() and also do it before device_unregister().

Fixes: 0328947 ("PCI: endpoint: Assign PCI domain number for endpoint controllers")
Signed-off-by: Zijun Hu <[email protected]>
Reviewed-by: Manivannan Sadhasivam <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[mani: reworded subject and description]
Signed-off-by: Manivannan Sadhasivam <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>
Signed-off-by: Krzysztof Wilczyński <[email protected]>
Cc: [email protected]

Author: Zijun Hu

drivers/pci/endpoint/pci-epc-core.c

@@ -923,11 +923,10 @@ EXPORT_SYMBOL_GPL(pci_epc_bus_master_enable_notify);
 void pci_epc_destroy(struct pci_epc *epc)
 {
 	pci_ep_cfs_remove_epc_group(epc->group);
-	device_unregister(&epc->dev);
-
 #ifdef CONFIG_PCI_DOMAINS_GENERIC
-	pci_bus_release_domain_nr(&epc->dev, epc->domain_nr);
+	pci_bus_release_domain_nr(epc->dev.parent, epc->domain_nr);
 #endif
+	device_unregister(&epc->dev);
 }
 EXPORT_SYMBOL_GPL(pci_epc_destroy);