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

From: Colin King
Date: Fri Sep 22 2017 - 09:41:43 EST


From: Colin Ian King <colin.king@xxxxxxxxxxxxx>

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.king@xxxxxxxxxxxxx>
---
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