SUNRPC: Ensure that the gssproxy client can start in a connected state

Ensure that the gssproxy client connects to the server from the gssproxy
daemon process context so that the AF_LOCAL socket connection is done
using the correct path and namespaces.

Fixes: 1d65833 ("SUNRPC: Add RPC based upcall mechanism for RPCGSS auth")
Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Author: Trond Myklebust

include/linux/sunrpc/clnt.h

@@ -160,6 +160,7 @@ struct rpc_add_xprt_test {
 #define RPC_CLNT_CREATE_NO_RETRANS_TIMEOUT	(1UL << 9)
 #define RPC_CLNT_CREATE_SOFTERR		(1UL << 10)
 #define RPC_CLNT_CREATE_REUSEPORT	(1UL << 11)
+#define RPC_CLNT_CREATE_CONNECTED	(1UL << 12)
 
 struct rpc_clnt *rpc_create(struct rpc_create_args *args);
 struct rpc_clnt	*rpc_bind_new_program(struct rpc_clnt *,

net/sunrpc/auth_gss/gss_rpc_upcall.c

@@ -98,6 +98,7 @@ static int gssp_rpc_create(struct net *net, struct rpc_clnt **_clnt)
 		 * done without the correct namespace:
 		 */
 		.flags		= RPC_CLNT_CREATE_NOPING |
+				  RPC_CLNT_CREATE_CONNECTED |
 				  RPC_CLNT_CREATE_NO_IDLE_TIMEOUT
 	};
 	struct rpc_clnt *clnt;

net/sunrpc/clnt.c

@@ -76,6 +76,7 @@ static int	rpc_encode_header(struct rpc_task *task,
 static int	rpc_decode_header(struct rpc_task *task,
 				  struct xdr_stream *xdr);
 static int	rpc_ping(struct rpc_clnt *clnt);
+static int	rpc_ping_noreply(struct rpc_clnt *clnt);
 static void	rpc_check_timeout(struct rpc_task *task);
 
 static void rpc_register_client(struct rpc_clnt *clnt)
@@ -483,6 +484,12 @@ static struct rpc_clnt *rpc_create_xprt(struct rpc_create_args *args,
 			rpc_shutdown_client(clnt);
 			return ERR_PTR(err);
 		}
+	} else if (args->flags & RPC_CLNT_CREATE_CONNECTED) {
+		int err = rpc_ping_noreply(clnt);
+		if (err != 0) {
+			rpc_shutdown_client(clnt);
+			return ERR_PTR(err);
+		}
 	}
 
 	clnt->cl_softrtry = 1;
@@ -2709,6 +2716,10 @@ static const struct rpc_procinfo rpcproc_null = {
 	.p_decode = rpcproc_decode_null,
 };
 
+static const struct rpc_procinfo rpcproc_null_noreply = {
+	.p_encode = rpcproc_encode_null,
+};
+
 static void
 rpc_null_call_prepare(struct rpc_task *task, void *data)
 {
@@ -2762,6 +2773,28 @@ static int rpc_ping(struct rpc_clnt *clnt)
 	return status;
 }
 
+static int rpc_ping_noreply(struct rpc_clnt *clnt)
+{
+	struct rpc_message msg = {
+		.rpc_proc = &rpcproc_null_noreply,
+	};
+	struct rpc_task_setup task_setup_data = {
+		.rpc_client = clnt,
+		.rpc_message = &msg,
+		.callback_ops = &rpc_null_ops,
+		.flags = RPC_TASK_SOFT | RPC_TASK_SOFTCONN | RPC_TASK_NULLCREDS,
+	};
+	struct rpc_task	*task;
+	int status;
+
+	task = rpc_run_task(&task_setup_data);
+	if (IS_ERR(task))
+		return PTR_ERR(task);
+	status = task->tk_status;
+	rpc_put_task(task);
+	return status;
+}
+
 struct rpc_cb_add_xprt_calldata {
 	struct rpc_xprt_switch *xps;
 	struct rpc_xprt *xprt;