inet: RCU changes in inetdev_by_index()

Convert inetdev_by_index() to not increment in_dev refcount.

Callers hold RCU or RTNL, and should not decrement in_dev refcount.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 9d421f4..d0ffcbe 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1245,10 +1245,8 @@
 	if (ipv4_is_multicast(t->parms.iph.daddr) && t->mlink) {
 		struct in_device *in_dev;
 		in_dev = inetdev_by_index(dev_net(dev), t->mlink);
-		if (in_dev) {
+		if (in_dev)
 			ip_mc_dec_group(in_dev, t->parms.iph.daddr);
-			in_dev_put(in_dev);
-		}
 	}
 	return 0;
 }