[PATCH][V2] e1000: avoid null pointer dereference on invalid stat type

[Colin King]

From: Colin Ian King <colin.k...@canonical.com>

Currently if the stat type is invalid then data[i] is being set
either by dereferencing a null pointer p, or it is reading from
an incorrect previous location if we had a valid stat type
previously.  Fix this by nullify pointer p if a stat type is
invalid and only setting data if p is not null.

Detected by CoverityScan, CID#113385 ("Explicit null dereferenced")

Signed-off-by: Colin Ian King <colin.k...@canonical.com>
---
 drivers/net/ethernet/intel/e1000/e1000_ethtool.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000/e1000_ethtool.c 
b/drivers/net/ethernet/intel/e1000/e1000_ethtool.c
index ec8aa4562cc9..724c93a6ea92 100644
--- a/drivers/net/ethernet/intel/e1000/e1000_ethtool.c
+++ b/drivers/net/ethernet/intel/e1000/e1000_ethtool.c
@@ -1824,7 +1824,7 @@ static void e1000_get_ethtool_stats(struct net_device 
*netdev,
 {
        struct e1000_adapter *adapter = netdev_priv(netdev);
        int i;
-       char *p = NULL;
+       char *p;
        const struct e1000_stats *stat = e1000_gstrings_stats;
 
        e1000_update_stats(adapter);
@@ -1837,16 +1837,18 @@ static void e1000_get_ethtool_stats(struct net_device 
*netdev,
                        p = (char *)adapter + stat->stat_offset;
                        break;
                default:
+                       p = NULL;
                        WARN_ONCE(1, "Invalid E1000 stat type: %u index %d\n",
                                  stat->type, i);
                        break;
                }
 
-               if (stat->sizeof_stat == sizeof(u64))
-                       data[i] = *(u64 *)p;
-               else
-                       data[i] = *(u32 *)p;
-
+               if (p) {
+                       if (stat->sizeof_stat == sizeof(u64))
+                               data[i] = *(u64 *)p;
+                       else
+                               data[i] = *(u32 *)p;
+               }
                stat++;
        }
 /* BUG_ON(i != E1000_STATS_LEN); */
-- 
2.14.1