SUNRPC: If the rpcbind channel is disconnected, fail the call to unregister

If rpcbind causes our connection to the AF_LOCAL socket to close after
we've registered a service, then we want to be careful about reconnecting
since the mount namespace may have changed.

By simply refusing to reconnect the AF_LOCAL socket in the case of
unregister, we avoid the need to somehow save the mount namespace. While
this may lead to some services not unregistering properly, it should
be safe.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Nix <nix@esperi.org.uk>
Cc: Jeff Layton <jlayton@redhat.com>
Cc: stable@vger.kernel.org # 3.9.x

include/linux/sunrpc/sched.h

@@ -121,6 +121,7 @@ struct rpc_task_setup {
 #define RPC_TASK_SOFTCONN	0x0400		/* Fail if can't connect */
 #define RPC_TASK_SENT		0x0800		/* message was sent */
 #define RPC_TASK_TIMEOUT	0x1000		/* fail with ETIMEDOUT on timeout */
+#define RPC_TASK_NOCONNECT	0x2000		/* return ENOTCONN if not connected */
 
 #define RPC_IS_ASYNC(t)		((t)->tk_flags & RPC_TASK_ASYNC)
 #define RPC_IS_SWAPPER(t)	((t)->tk_flags & RPC_TASK_SWAPPER)

net/sunrpc/clnt.c

@@ -1660,6 +1660,10 @@ call_connect(struct rpc_task *task)
 		task->tk_action = call_connect_status;
 		if (task->tk_status < 0)
 			return;
+		if (task->tk_flags & RPC_TASK_NOCONNECT) {
+			rpc_exit(task, -ENOTCONN);
+			return;
+		}
 		xprt_connect(task);
 	}
 }

net/sunrpc/netns.h

@@ -23,6 +23,7 @@ struct sunrpc_net {
 	struct rpc_clnt *rpcb_local_clnt4;
 	spinlock_t rpcb_clnt_lock;
 	unsigned int rpcb_users;
+	unsigned int rpcb_is_af_local : 1;
 
 	struct mutex gssp_lock;
 	wait_queue_head_t gssp_wq;

net/sunrpc/rpcb_clnt.c

@@ -204,13 +204,15 @@ void rpcb_put_local(struct net *net)
 }
 
 static void rpcb_set_local(struct net *net, struct rpc_clnt *clnt,
-			struct rpc_clnt *clnt4)
+			struct rpc_clnt *clnt4,
+			bool is_af_local)
 {
 	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
 
 	/* Protected by rpcb_create_local_mutex */
 	sn->rpcb_local_clnt = clnt;
 	sn->rpcb_local_clnt4 = clnt4;
+	sn->rpcb_is_af_local = is_af_local ? 1 : 0;
 	smp_wmb(); 
 	sn->rpcb_users = 1;
 	dprintk("RPC:       created new rpcb local clients (rpcb_local_clnt: "
@@ -271,7 +273,7 @@ static int rpcb_create_local_unix(struct net *net)
 		clnt4 = NULL;
 	}
 
-	rpcb_set_local(net, clnt, clnt4);
+	rpcb_set_local(net, clnt, clnt4, true);
 
 out:
 	return result;
@@ -323,7 +325,7 @@ static int rpcb_create_local_net(struct net *net)
 		clnt4 = NULL;
 	}
 
-	rpcb_set_local(net, clnt, clnt4);
+	rpcb_set_local(net, clnt, clnt4, false);
 
 out:
 	return result;
@@ -384,13 +386,16 @@ static struct rpc_clnt *rpcb_create(struct net *net, const char *hostname,
 	return rpc_create(&args);
 }
 
-static int rpcb_register_call(struct rpc_clnt *clnt, struct rpc_message *msg)
+static int rpcb_register_call(struct sunrpc_net *sn, struct rpc_clnt *clnt, struct rpc_message *msg, bool is_set)
 {
-	int result, error = 0;
+	int flags = RPC_TASK_NOCONNECT;
+	int error, result = 0;
 
+	if (is_set || !sn->rpcb_is_af_local)
+		flags = RPC_TASK_SOFTCONN;
 	msg->rpc_resp = &result;
 
-	error = rpc_call_sync(clnt, msg, RPC_TASK_SOFTCONN);
+	error = rpc_call_sync(clnt, msg, flags);
 	if (error < 0) {
 		dprintk("RPC:       failed to contact local rpcbind "
 				"server (errno %d).\n", -error);
@@ -447,16 +452,19 @@ int rpcb_register(struct net *net, u32 prog, u32 vers, int prot, unsigned short
 		.rpc_argp	= &map,
 	};
 	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
+	bool is_set = false;
 
 	dprintk("RPC:       %sregistering (%u, %u, %d, %u) with local "
 			"rpcbind\n", (port ? "" : "un"),
 			prog, vers, prot, port);
 
 	msg.rpc_proc = &rpcb_procedures2[RPCBPROC_UNSET];
-	if (port)
+	if (port != 0) {
 		msg.rpc_proc = &rpcb_procedures2[RPCBPROC_SET];
+		is_set = true;
+	}
 
-	return rpcb_register_call(sn->rpcb_local_clnt, &msg);
+	return rpcb_register_call(sn, sn->rpcb_local_clnt, &msg, is_set);
 }
 
 /*
@@ -469,6 +477,7 @@ static int rpcb_register_inet4(struct sunrpc_net *sn,
 	const struct sockaddr_in *sin = (const struct sockaddr_in *)sap;
 	struct rpcbind_args *map = msg->rpc_argp;
 	unsigned short port = ntohs(sin->sin_port);
+	bool is_set = false;
 	int result;
 
 	map->r_addr = rpc_sockaddr2uaddr(sap, GFP_KERNEL);
@@ -479,10 +488,12 @@ static int rpcb_register_inet4(struct sunrpc_net *sn,
 			map->r_addr, map->r_netid);
 
 	msg->rpc_proc = &rpcb_procedures4[RPCBPROC_UNSET];
-	if (port)
+	if (port != 0) {
 		msg->rpc_proc = &rpcb_procedures4[RPCBPROC_SET];
+		is_set = true;
+	}
 
-	result = rpcb_register_call(sn->rpcb_local_clnt4, msg);
+	result = rpcb_register_call(sn, sn->rpcb_local_clnt4, msg, is_set);
 	kfree(map->r_addr);
 	return result;
 }
@@ -497,6 +508,7 @@ static int rpcb_register_inet6(struct sunrpc_net *sn,
 	const struct sockaddr_in6 *sin6 = (const struct sockaddr_in6 *)sap;
 	struct rpcbind_args *map = msg->rpc_argp;
 	unsigned short port = ntohs(sin6->sin6_port);
+	bool is_set = false;
 	int result;
 
 	map->r_addr = rpc_sockaddr2uaddr(sap, GFP_KERNEL);
@@ -507,10 +519,12 @@ static int rpcb_register_inet6(struct sunrpc_net *sn,
 			map->r_addr, map->r_netid);
 
 	msg->rpc_proc = &rpcb_procedures4[RPCBPROC_UNSET];
-	if (port)
+	if (port != 0) {
 		msg->rpc_proc = &rpcb_procedures4[RPCBPROC_SET];
+		is_set = true;
+	}
 
-	result = rpcb_register_call(sn->rpcb_local_clnt4, msg);
+	result = rpcb_register_call(sn, sn->rpcb_local_clnt4, msg, is_set);
 	kfree(map->r_addr);
 	return result;
 }
@@ -527,7 +541,7 @@ static int rpcb_unregister_all_protofamilies(struct sunrpc_net *sn,
 	map->r_addr = "";
 	msg->rpc_proc = &rpcb_procedures4[RPCBPROC_UNSET];
 
-	return rpcb_register_call(sn->rpcb_local_clnt4, msg);
+	return rpcb_register_call(sn, sn->rpcb_local_clnt4, msg, false);
 }
 
 /**