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Subject[PATCH] e1000: avoid null pointer dereference on invalid stat type
Date
From: Colin Ian King <colin.king@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.king@canonical.com>
---
drivers/net/ethernet/intel/e1000/e1000_ethtool.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000/e1000_ethtool.c b/drivers/net/ethernet/intel/e1000/e1000_ethtool.c
index ec8aa4562cc9..2ef6f08b580b 100644
--- a/drivers/net/ethernet/intel/e1000/e1000_ethtool.c
+++ b/drivers/net/ethernet/intel/e1000/e1000_ethtool.c
@@ -1824,11 +1824,12 @@ static void e1000_get_ethtool_stats(struct net_device *netdev,
{
struct e1000_adapter *adapter = netdev_priv(netdev);
int i;
- char *p = NULL;
const struct e1000_stats *stat = e1000_gstrings_stats;

e1000_update_stats(adapter);
for (i = 0; i < E1000_GLOBAL_STATS_LEN; i++) {
+ char *p;
+
switch (stat->type) {
case NETDEV_STATS:
p = (char *)netdev + stat->stat_offset;
@@ -1837,12 +1838,13 @@ 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))
+ if (p && stat->sizeof_stat == sizeof(u64))
data[i] = *(u64 *)p;
else
data[i] = *(u32 *)p;
--
2.14.1
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