PCI ASPM: fix possible null pointer dereference

Fix possible NULL dereference in pcie_aspm_exit_link_state(). This
patch also cleanup some code.

Acked-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

1 files changed, 9 insertions, 8 deletions

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 638881b00f6b..0800c5146826 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -665,16 +665,16 @@ out:
 void pcie_aspm_exit_link_state(struct pci_dev *pdev)
 {
         struct pci_dev *parent = pdev->bus->self;
-        struct pcie_link_state *link_state = parent->link_state;
+        struct pcie_link_state *link;
 
-        if (aspm_disabled || !pdev->is_pcie || !parent || !link_state)
+        if (aspm_disabled || !pdev->is_pcie || !parent || !parent->link_state)
                 return;
         if (parent->pcie_type != PCI_EXP_TYPE_ROOT_PORT &&
-                parent->pcie_type != PCI_EXP_TYPE_DOWNSTREAM)
+            parent->pcie_type != PCI_EXP_TYPE_DOWNSTREAM)
                 return;
+
         down_read(&pci_bus_sem);
         mutex_lock(&aspm_lock);
-
         /*
          * All PCIe functions are in one slot, remove one function will remove
          * the whole slot, so just wait until we are the last function left.
@@ -682,13 +682,14 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
         if (!list_is_last(&pdev->bus_list, &parent->subordinate->devices))
                 goto out;
 
+        link = parent->link_state;
+
         /* All functions are removed, so just disable ASPM for the link */
         __pcie_aspm_config_one_dev(parent, 0);
-        list_del(&link_state->sibling);
-        list_del(&link_state->link);
+        list_del(&link->sibling);
+        list_del(&link->link);
         /* Clock PM is for endpoint device */
-
-        free_link_state(link_state);
+        free_link_state(link);
 out:
         mutex_unlock(&aspm_lock);
         up_read(&pci_bus_sem);