PCIe: AER: during disable, check subordinate before walking

Commit 47a8b0cc (Enable PCIe AER only after checking firmware
support) wants to walk the PCI bus in the remove path to disable
AER, and calls pci_walk_bus for downstream bridges.

Unfortunately, in the remove path, we remove devices and bridges
in a depth-first manner, starting with the furthest downstream
bridge and working our way backwards.

The furthest downstream bridges will not have a dev->subordinate,
and we hit a NULL deref in pci_walk_bus.

Check for dev->subordinate first before attempting to walk the
PCI hierarchy below us.

Acked-by: Andrew Patterson <andrew.patterson@hp.com>
Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>

diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c
index d0c9736858689f62f19dc6fd85572dacc3c2d3ec..38257500738223486758e337cb49d7184ddcef5a 100644 (file)
--- a/drivers/pci/pcie/aer/aerdrv_core.c
+++ b/drivers/pci/pcie/aer/aerdrv_core.c
@@ -133,6 +133,9 @@ static void set_downstream_devices_error_reporting(struct pci_dev *dev,
                                                   bool enable)
 {
        set_device_error_reporting(dev, &enable);
+
+       if (!dev->subordinate)
+               return;
        pci_walk_bus(dev->subordinate, set_device_error_reporting, &enable);
 }