PCI: Don't scan random busses in pci_scan_bridge()

When assigning a new bus number in pci_scan_bridge we check whether
max+1 is free by calling pci_find_bus. If it does already exist then we
assume that we are rescanning and that this is the right bus to scan.

This is fragile. If max+1 lies outside of bus->busn_res.end then we will
rescan some random bus from somewhere else in the hierachy. This patch
checks for this case and prints a warning.

[bhelgaas: add parent/child bus number info to dev_warn()]
Signed-off-by: Andreas Noever <andreas.noever@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 1436288924c3..509494381a7a 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -829,12 +829,16 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
                         goto out;
                 }
 
+                if (max >= bus->busn_res.end) {
+                        dev_warn(&dev->dev, "can't allocate child bus %02x from %pR\n",
+                                 max, &bus->busn_res);
+                        goto out;
+                }
+
                 /* Clear errors */
                 pci_write_config_word(dev, PCI_STATUS, 0xffff);
 
-                /* Prevent assigning a bus number that already exists.
-                 * This can happen when a bridge is hot-plugged, so in
-                 * this case we only re-scan this bus. */
+                /* The bus will already exist if we are rescanning */
                 child = pci_find_bus(pci_domain_nr(bus), max+1);
                 if (!child) {
                         child = pci_add_new_bus(bus, dev, max+1);