e1000: remove races when changing mtu

this patch fixes a bug that occurs when routing packets and simultaneously
changing the mtu.  the rx_buffer_len variable is used during the rx cleanup
and if that changes on the fly without stopping traffic bad things happen

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 2 deletions

diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c
index cdbf4fb8150d..2178e0d39c01 100644
--- a/drivers/net/e1000/e1000_main.c
+++ b/drivers/net/e1000/e1000_main.c
@@ -3141,6 +3141,13 @@ static int e1000_change_mtu(struct net_device *netdev, int new_mtu)
                 break;
         }
 
+        while (test_and_set_bit(__E1000_RESETTING, &adapter->flags))
+                msleep(1);
+        /* e1000_down has a dependency on max_frame_size */
+        hw->max_frame_size = max_frame;
+        if (netif_running(netdev))
+                e1000_down(adapter);
+
         /* NOTE: netdev_alloc_skb reserves 16 bytes, and typically NET_IP_ALIGN
          * means we reserve 2 more, this pushes us to allocate from the next
          * larger slab size.
@@ -3169,11 +3176,16 @@ static int e1000_change_mtu(struct net_device *netdev, int new_mtu)
              (max_frame == MAXIMUM_ETHERNET_VLAN_SIZE)))
                 adapter->rx_buffer_len = MAXIMUM_ETHERNET_VLAN_SIZE;
 
+        printk(KERN_INFO "e1000: %s changing MTU from %d to %d\n",
+               netdev->name, netdev->mtu, new_mtu);
         netdev->mtu = new_mtu;
-        hw->max_frame_size = max_frame;
 
         if (netif_running(netdev))
-                e1000_reinit_locked(adapter);
+                e1000_up(adapter);
+        else
+                e1000_reset(adapter);
+
+        clear_bit(__E1000_RESETTING, &adapter->flags);
 
         return 0;
 }