powerpc/eeh: avoid possible crash when edev->pdev changes

If a PCI device is removed during eeh_pe_report_edev(), edev->pdev
will change and can cause a crash, hold the PCI rescan/remove lock
while taking a copy of edev->pdev->bus.

Signed-off-by: Ganesh Goudar <ganeshgr@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240617140240.580453-1-ganeshgr@linux.ibm.com

Author: Ganesh Goudar

arch/powerpc/kernel/eeh_pe.c

@@ -849,6 +849,7 @@ struct pci_bus *eeh_pe_bus_get(struct eeh_pe *pe)
 {
 	struct eeh_dev *edev;
 	struct pci_dev *pdev;
+	struct pci_bus *bus = NULL;
 
 	if (pe->type & EEH_PE_PHB)
 		return pe->phb->bus;
@@ -859,9 +860,11 @@ struct pci_bus *eeh_pe_bus_get(struct eeh_pe *pe)
 
 	/* Retrieve the parent PCI bus of first (top) PCI device */
 	edev = list_first_entry_or_null(&pe->edevs, struct eeh_dev, entry);
+	pci_lock_rescan_remove();
 	pdev = eeh_dev_to_pci_dev(edev);
 	if (pdev)
-		return pdev->bus;
+		bus = pdev->bus;
+	pci_unlock_rescan_remove();
 
-	return NULL;
+	return bus;
 }