powerpc/eeh: Null check uses of eeh_pe_bus_get

commit 04fec21c upstream.

eeh_pe_bus_get() can return NULL if a PCI bus isn't found for a given PE.
Some callers don't check this, and can cause a null pointer dereference
under certain circumstances.

Fix this by checking NULL everywhere eeh_pe_bus_get() is called.

Fixes: 8a6b1bc7 ("powerpc/eeh: EEH core to handle special event")
Signed-off-by: Russell Currey <ruscur@russell.cc>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

arch/powerpc/kernel/eeh_driver.c

@@ -697,6 +697,14 @@ static void eeh_handle_special_event(void)
 
 				/* Notify all devices to be down */
 				bus = eeh_pe_bus_get(phb_pe);
+				if (!bus) {
+					pr_err("%s: Cannot find PCI bus for "
+					       "PHB#%d-PE#%x\n",
+					       __func__,
+					       pe->phb->global_number,
+					       pe->addr);
+					break;
+				}
 				eeh_pe_dev_traverse(pe,
 					eeh_report_failure, NULL);
 				pcibios_remove_pci_devices(bus);

arch/powerpc/platforms/powernv/eeh-ioda.c

@@ -493,6 +493,11 @@ static int ioda_eeh_reset(struct eeh_pe *pe, int option)
 		ret = ioda_eeh_phb_reset(hose, option);
 	} else {
 		bus = eeh_pe_bus_get(pe);
+		if (!bus) {
+			pr_err("%s: Cannot find PCI bus for PHB#%d-PE#%x\n",
+			       __func__, pe->phb->global_number, pe->addr);
+			return -EIO;
+		}
 		if (pci_is_root_bus(bus) ||
 		    pci_is_root_bus(bus->parent))
 			ret = ioda_eeh_root_reset(hose, option);