Fix pointer dereference before call to pcie_bus_configure_settings

Commit b03e7495a862 ("PCI: Set PCI-E Max Payload Size on fabric")
introduced a potential NULL pointer dereference in calls to
pcie_bus_configure_settings due to attempts to access pci_bus self
variables when the self pointer is NULL.

To correct this, verify that the self pointer in pci_bus is non-NULL
before dereferencing it.

Reported-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Shyam Iyer <shyam_iyer@dell.com>
Signed-off-by: Jon Mason <mason@myri.com>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
index c95330267f08..039d91315bc5 100644
--- a/arch/x86/pci/acpi.c
+++ b/arch/x86/pci/acpi.c
@@ -365,8 +365,13 @@ struct pci_bus * __devinit pci_acpi_scan_root(struct acpi_pci_root *root)
          */
         if (bus) {
                 struct pci_bus *child;
-                list_for_each_entry(child, &bus->children, node)
-                        pcie_bus_configure_settings(child, child->self->pcie_mpss);
+                list_for_each_entry(child, &bus->children, node) {
+                        struct pci_dev *self = child->self;
+                        if (!self)
+                                continue;
+
+                        pcie_bus_configure_settings(child, self->pcie_mpss);
+                }
         }
 
         if (!bus)