PCI: Pass domain number to pci_bus_release_domain_nr() explicitly

The pci_bus_release_domain_nr() API is supposed to free the domain
number allocated by pci_bus_find_domain_nr(). Most of the callers of
pci_bus_find_domain_nr(), store the domain number in pci_bus::domain_nr.

As such, the pci_bus_release_domain_nr() implicitly frees the domain
number by dereferencing 'struct pci_bus'. However, one of the callers
of this API, the PCI endpoint subsystem, doesn't have 'struct pci_bus',
so it only passes NULL. Due to this, the API will end up dereferencing
the NULL pointer.

To fix this issue, pass the domain number to this API explicitly. Since
'struct pci_bus' is not used for anything else other than extracting the
domain number, it makes sense to pass the domain number directly.

Fixes: 0328947c5032 ("PCI: endpoint: Assign PCI domain number for endpoint controllers")
Closes: https://lore.kernel.org/linux-pci/[e-mail]
Link: https://lore.kernel.org/linux-pci/[e-mail]
Reported-by: Dan Carpenter <[e-mail]>
Signed-off-by: Manivannan Sadhasivam <[e-mail]>
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <[e-mail]>

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

···
 	device_unregister(&epc->dev);
 
 #ifdef CONFIG_PCI_DOMAINS_GENERIC
-	pci_bus_release_domain_nr(NULL, &epc->dev);
+	pci_bus_release_domain_nr(&epc->dev, epc->domain_nr);
 #endif
 }
 EXPORT_SYMBOL_GPL(pci_epc_destroy);

drivers/pci/pci.c

···
 	return ida_alloc(&pci_domain_nr_dynamic_ida, GFP_KERNEL);
 }
 
-static void of_pci_bus_release_domain_nr(struct pci_bus *bus, struct device *parent)
+static void of_pci_bus_release_domain_nr(struct device *parent, int domain_nr)
 {
-	if (bus->domain_nr < 0)
+	if (domain_nr < 0)
 		return;
 
 	/* Release domain from IDA where it was allocated. */
-	if (of_get_pci_domain_nr(parent->of_node) == bus->domain_nr)
-		ida_free(&pci_domain_nr_static_ida, bus->domain_nr);
+	if (of_get_pci_domain_nr(parent->of_node) == domain_nr)
+		ida_free(&pci_domain_nr_static_ida, domain_nr);
 	else
-		ida_free(&pci_domain_nr_dynamic_ida, bus->domain_nr);
+		ida_free(&pci_domain_nr_dynamic_ida, domain_nr);
 }
 
 int pci_bus_find_domain_nr(struct pci_bus *bus, struct device *parent)
···
 			       acpi_pci_bus_find_domain_nr(bus);
 }
 
-void pci_bus_release_domain_nr(struct pci_bus *bus, struct device *parent)
+void pci_bus_release_domain_nr(struct device *parent, int domain_nr)
 {
 	if (!acpi_disabled)
 		return;
-	of_pci_bus_release_domain_nr(bus, parent);
+	of_pci_bus_release_domain_nr(parent, domain_nr);
 }
 #endif
 

drivers/pci/probe.c

···
 
 free:
 #ifdef CONFIG_PCI_DOMAINS_GENERIC
-	pci_bus_release_domain_nr(bus, parent);
+	pci_bus_release_domain_nr(parent, bus->domain_nr);
 #endif
 	kfree(bus);
 	return err;

drivers/pci/remove.c

···
 #ifdef CONFIG_PCI_DOMAINS_GENERIC
 	/* Release domain_nr if it was dynamically allocated */
 	if (host_bridge->domain_nr == PCI_DOMAIN_NR_NOT_SET)
-		pci_bus_release_domain_nr(bus, host_bridge->dev.parent);
+		pci_bus_release_domain_nr(host_bridge->dev.parent, bus->domain_nr);
 #endif
 
 	pci_remove_bus(bus);

include/linux/pci.h

···
 { return 0; }
 #endif
 int pci_bus_find_domain_nr(struct pci_bus *bus, struct device *parent);
-void pci_bus_release_domain_nr(struct pci_bus *bus, struct device *parent);
+void pci_bus_release_domain_nr(struct device *parent, int domain_nr);
 #endif
 
 /* Some architectures require additional setup to direct VGA traffic */