pci: Don't crash when reading mpss from root complex

In pcie_find_smpss(), we have the following statement:

 	if (dev->is_hotplug_bridge && (!list_is_singular(&dev->bus->devices) ||
	    dev->bus->self->pcie_type != PCI_EXP_TYPE_ROOT_PORT))

The problem is that at least on my machine, this gets called for the
root complex (virtual P2P bridge), and dev->bus->self is NULL since
the parent bus for this is not itself anchor to a PCI device.

This adds the necessary NULL check.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Jon Mason <mason@myri.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index b1187ff..f3f94a5 100644 (file)
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1351,7 +1351,8 @@ static int pcie_find_smpss(struct pci_dev *dev, void *data)
         * will occur as normal.
         */
        if (dev->is_hotplug_bridge && (!list_is_singular(&dev->bus->devices) ||
-           dev->bus->self->pcie_type != PCI_EXP_TYPE_ROOT_PORT))
+            (dev->bus->self &&
+             dev->bus->self->pcie_type != PCI_EXP_TYPE_ROOT_PORT)))
                *smpss = 0;
 
        if (*smpss > dev->pcie_mpss)