RDMA/core: Fix double put of resource

Do not decrease the reference count of resource tracker object twice in
the error flow of res_get_common_doit.

Fixes: c5dfe0e ("RDMA/nldev: Add resource tracker doit callback")
Link: https://lore.kernel.org/r/20200507062942.98305-1-leon@kernel.org
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/nldev.c

@@ -1292,11 +1292,10 @@ static int res_get_common_doit(struct sk_buff *skb, struct nlmsghdr *nlh,
 	has_cap_net_admin = netlink_capable(skb, CAP_NET_ADMIN);
 
 	ret = fill_func(msg, has_cap_net_admin, res, port);
-
-	rdma_restrack_put(res);
 	if (ret)
 		goto err_free;
 
+	rdma_restrack_put(res);
 	nlmsg_end(msg, nlh);
 	ib_device_put(device);
 	return rdma_nl_unicast(sock_net(skb->sk), msg, NETLINK_CB(skb).portid);