infiniband: make sure the src net is infiniband when create new link

When we create a new infiniband link with uninfiniband device, e.g. `ip link
add link em1 type ipoib pkey 0x8001`. We will get a NULL pointer dereference
cause other dev like Ethernet don't have struct ib_device.

The code path is:
rtnl_newlink
  |-- ipoib_new_child_link
        |-- __ipoib_vlan_add
              |-- ipoib_set_dev_features
                    |-- ib_query_device

Fix this bug by make sure the src net is infiniband when create new link.
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/infiniband/ulp/ipoib/ipoib_netlink.c

@@ -31,6 +31,7 @@
  */
 
 #include <linux/netdevice.h>
+#include <linux/if_arp.h>      /* For ARPHRD_xxx */
 #include <linux/module.h>
 #include <net/rtnetlink.h>
 #include "ipoib.h"
@@ -103,7 +104,7 @@ static int ipoib_new_child_link(struct net *src_net, struct net_device *dev,
 		return -EINVAL;
 
 	pdev = __dev_get_by_index(src_net, nla_get_u32(tb[IFLA_LINK]));
-	if (!pdev)
+	if (!pdev || pdev->type != ARPHRD_INFINIBAND)
 		return -ENODEV;
 
 	ppriv = netdev_priv(pdev);