decnet: use __dev_get_by_index instead of dev_get_by_index to find interface

The following call chain we can identify that dn_cache_getroute() is
protected under rtnl_lock. So if we use __dev_get_by_index() instead
of dev_get_by_index() to find interface handlers in it, this would help
us avoid to change interface reference counter.

rtnetlink_rcv()
  rtnl_lock()
    netlink_rcv_skb()
      dn_cache_getroute()
  rtnl_unlock()

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 8 deletions

diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index ad2efa5b861b..ce0cbbfe0f43 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -1666,12 +1666,8 @@ static int dn_cache_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh)
 
         if (fld.flowidn_iif) {
                 struct net_device *dev;
-                if ((dev = dev_get_by_index(&init_net, fld.flowidn_iif)) == NULL) {
-                        kfree_skb(skb);
-                        return -ENODEV;
-                }
-                if (!dev->dn_ptr) {
-                        dev_put(dev);
+                dev = __dev_get_by_index(&init_net, fld.flowidn_iif);
+                if (!dev || !dev->dn_ptr) {
                         kfree_skb(skb);
                         return -ENODEV;
                 }
@@ -1693,8 +1689,6 @@ static int dn_cache_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh)
                 err = dn_route_output_key((struct dst_entry **)&rt, &fld, 0);
         }
 
-        if (skb->dev)
-                dev_put(skb->dev);
         skb->dev = NULL;
         if (err)
                 goto out_free;