ixgb: fix bug when freeing resources

It was pointed out by Breno Leitao <leitao@linux.vnet.ibm.com> that
ixgb would crash on PPC when an IOMMU was in use, if change_mtu was
called.

It appears to be a pretty simple issue in the driver that wasn't discovered
because most systems don't run with an IOMMU.  The driver needs to only unmap
buffers that are mapped (duh).

CC: Breno Leitao <leitao@linux.vnet.ibm.com>

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/net/ixgb/ixgb_main.c b/drivers/net/ixgb/ixgb_main.c
index aa75385cd6c7..be3c7dc96f63 100644
--- a/drivers/net/ixgb/ixgb_main.c
+++ b/drivers/net/ixgb/ixgb_main.c
@@ -977,15 +977,17 @@ ixgb_clean_rx_ring(struct ixgb_adapter *adapter)
 
         for (i = 0; i < rx_ring->count; i++) {
                 buffer_info = &rx_ring->buffer_info[i];
-                if (buffer_info->skb) {
-
+                if (buffer_info->dma) {
                         pci_unmap_single(pdev,
                                          buffer_info->dma,
                                          buffer_info->length,
                                          PCI_DMA_FROMDEVICE);
+                        buffer_info->dma = 0;
+                        buffer_info->length = 0;
+                }
 
+                if (buffer_info->skb) {
                         dev_kfree_skb(buffer_info->skb);
-
                         buffer_info->skb = NULL;
                 }
         }