[PATCH] netvsc: fix dereference before null check errors

From: Colin King
Date: Sat Mar 25 2017 - 10:27:00 EST


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

ndev is being checked to see if it is a null pointer however before
the null check ndev is being dereferenced; hence there is a potential
null pointer dereference bug that needs fixing. Fix this by only
dereferencing ndev after the null check.

Detected by CoverityScan, CID#1420760, CID#140761 ("Dereference
before null check")

Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
---
drivers/net/hyperv/netvsc_drv.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index f830bbbd8ad4..f24c2891dd0c 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -1135,7 +1135,7 @@ static int netvsc_get_rxfh(struct net_device *dev, u32 *indir, u8 *key,
{
struct net_device_context *ndc = netdev_priv(dev);
struct netvsc_device *ndev = rcu_dereference(ndc->nvdev);
- struct rndis_device *rndis_dev = ndev->extension;
+ struct rndis_device *rndis_dev;
int i;

if (!ndev)
@@ -1144,6 +1144,7 @@ static int netvsc_get_rxfh(struct net_device *dev, u32 *indir, u8 *key,
if (hfunc)
*hfunc = ETH_RSS_HASH_TOP; /* Toeplitz */

+ rndis_dev = ndev->extension;
if (indir) {
for (i = 0; i < ITAB_NUM; i++)
indir[i] = rndis_dev->ind_table[i];
@@ -1160,7 +1161,7 @@ static int netvsc_set_rxfh(struct net_device *dev, const u32 *indir,
{
struct net_device_context *ndc = netdev_priv(dev);
struct netvsc_device *ndev = rtnl_dereference(ndc->nvdev);
- struct rndis_device *rndis_dev = ndev->extension;
+ struct rndis_device *rndis_dev;
int i;

if (!ndev)
@@ -1169,6 +1170,7 @@ static int netvsc_set_rxfh(struct net_device *dev, const u32 *indir,
if (hfunc != ETH_RSS_HASH_NO_CHANGE && hfunc != ETH_RSS_HASH_TOP)
return -EOPNOTSUPP;

+ rndis_dev = ndev->extension;
if (indir) {
for (i = 0; i < ITAB_NUM; i++)
if (indir[i] >= dev->num_rx_queues)
--
2.11.0