[PATCH] powerpc/pci: Fix PHB removal/rescan on PowerNV

["Cédric Le Goater" <clg@kaod.org>]

To fix an issue with PHB hotplug on pSeries machine (HPT/XIVE), commit
3a3181e16fbd introduced a PPC specific pcibios_remove_bus() routine to
clear all interrupt mappings when the bus is removed. This routine
frees an array allocated in pcibios_scan_phb().

This broke PHB hotplug on PowerNV because, when a PHB is removed and
re-scanned through sysfs, the PCI layer un-assigns and re-assigns
resources to the PHB but does not destroy and recreate the PCI
controller structure. Since pcibios_remove_bus() does not clear the
'irq_map' array pointer, a second removal of the PHB will try to free
the array a second time and corrupt memory.

Free the 'irq_map' array in pcibios_free_controller() to fix
corruption and clear interrupt mapping after it has been
disposed. This to avoid filling up the array with successive
remove/rescan of a bus.

Cc: "Oliver O'Halloran" <oohall@gmail.com>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>
Fixes: 3a3181e16fbd ("powerpc/pci: unmap legacy INTx interrupts when a PHB is removed")
Signed-off-by: Cédric Le Goater <clg@kaod.org>
---

Michael, I am not sure the Fixes tag is required. Feel free to drop
it. 

---
 arch/powerpc/kernel/pci-common.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index deb831f0ae13..6fc228e0359d 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -143,6 +143,8 @@ void pcibios_free_controller(struct pci_controller *phb)
 	list_del(&phb->list_node);
 	spin_unlock(&hose_spinlock);
 
+	kfree(phb->irq_map);
+
 	if (phb->is_dynamic)
 		kfree(phb);
 }
@@ -450,10 +452,10 @@ static void pci_irq_map_dispose(struct pci_bus *bus)
 
 	pr_debug("PCI: Clearing interrupt mappings for PHB %04x:%02x...\n",
 		 pci_domain_nr(bus), bus->number);
-	for (i = 0; i < phb->irq_count; i++)
+	for (i = 0; i < phb->irq_count; i++) {
 		irq_dispose_mapping(phb->irq_map[i]);
-
-	kfree(phb->irq_map);
+		phb->irq_map[i] = 0;
+	}
 }
 
 void pcibios_remove_bus(struct pci_bus *bus)
-- 
2.25.4