[PATCH] e1000: check the return of pci_get_drvdata() in e1000_remove()

[Bo Chen]

This check on pci_get_drvdata() prevents potential invalid pointer dereferences,
and is a common practice in *_remove() functions from other drivers, such as
'intel/e100.c', 'amd/pcnet32.c', 'realtek/8139too.c', and 'broadcom/tg3.c'.

Signed-off-by: Bo Chen <che...@pdx.edu>
---
 drivers/net/ethernet/intel/e1000/e1000_main.c | 41 ++++++++++---------
 1 file changed, 22 insertions(+), 19 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c 
b/drivers/net/ethernet/intel/e1000/e1000_main.c
index d5eb19b86a0a..7f63360dd221 100644
--- a/drivers/net/ethernet/intel/e1000/e1000_main.c
+++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
@@ -1283,32 +1283,35 @@ static int e1000_probe(struct pci_dev *pdev, const 
struct pci_device_id *ent)
 static void e1000_remove(struct pci_dev *pdev)
 {
        struct net_device *netdev = pci_get_drvdata(pdev);
-       struct e1000_adapter *adapter = netdev_priv(netdev);
-       struct e1000_hw *hw = &adapter->hw;
-       bool disable_dev;
 
-       e1000_down_and_stop(adapter);
-       e1000_release_manageability(adapter);
+       if (netdev) {
+               struct e1000_adapter *adapter = netdev_priv(netdev);
+               struct e1000_hw *hw = &adapter->hw;
+               bool disable_dev;
 
-       unregister_netdev(netdev);
+               e1000_down_and_stop(adapter);
+               e1000_release_manageability(adapter);
 
-       e1000_phy_hw_reset(hw);
+               unregister_netdev(netdev);
 
-       kfree(adapter->tx_ring);
-       kfree(adapter->rx_ring);
+               e1000_phy_hw_reset(hw);
 
-       if (hw->mac_type == e1000_ce4100)
-               iounmap(hw->ce4100_gbe_mdio_base_virt);
-       iounmap(hw->hw_addr);
-       if (hw->flash_address)
-               iounmap(hw->flash_address);
-       pci_release_selected_regions(pdev, adapter->bars);
+               kfree(adapter->tx_ring);
+               kfree(adapter->rx_ring);
 
-       disable_dev = !test_and_set_bit(__E1000_DISABLED, &adapter->flags);
-       free_netdev(netdev);
+               if (hw->mac_type == e1000_ce4100)
+                       iounmap(hw->ce4100_gbe_mdio_base_virt);
+               iounmap(hw->hw_addr);
+               if (hw->flash_address)
+                       iounmap(hw->flash_address);
+               pci_release_selected_regions(pdev, adapter->bars);
 
-       if (disable_dev)
-               pci_disable_device(pdev);
+               disable_dev = !test_and_set_bit(__E1000_DISABLED, 
&adapter->flags);
+               free_netdev(netdev);
+
+               if (disable_dev)
+                       pci_disable_device(pdev);
+       }
 }
 
 /**
-- 
2.17.0