PCI: Check for child busses which use more bus numbers than allocated

pci_scan_child_bus can (potentially) return a bus number higher than the
subordinate value of the child bus. Possible reasons are that bus numbers
are reserved for SR-IOV or for CardBus (SR-IOV is done without checks and
the CardBus checks are sketchy at best).

We clamp the returned value to the actual subordinate value and print a
warning if too many bus numbers are reserved.

[bhelgaas: whitespace]
Signed-off-by: Andreas Noever <andreas.noever@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index e5df03669470..1436288924c3 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -805,10 +805,12 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
                 }
 
                 cmax = pci_scan_child_bus(child);
-                if (cmax > max)
-                        max = cmax;
-                if (child->busn_res.end > max)
-                        max = child->busn_res.end;
+                if (cmax > subordinate)
+                        dev_warn(&dev->dev, "bridge has subordinate %02x but max busn %02x\n",
+                                 subordinate, cmax);
+                /* subordinate should equal child->busn_res.end */
+                if (subordinate > max)
+                        max = subordinate;
         } else {
                 /*
                  * We need to assign a number to this bus which we always