netvsc: fix dereference before null check errors

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@canonical.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index f830bbbd8ad476e11768cd96665e9ed248e0015d..f24c2891dd0cf3e9f65af49c83fd723ccbcbc5ee 100644 (file)
--- 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)