drbd: Restore late assigning of tconn->data.sock and meta.sock

With commit from Mon Mar 28 16:33:12 2011 +0200
"drbd: drbd_connect(): Initialize struct drbd_socket before sending anything"

tconn->data.sock and tconn->meta.sock get assigned early, in
conn_connect.

The early assigning can trigger an OOPS, because it may released the socket
without acquiring the mutex protecting the socket. An other thread (worker)
might use setsockopt() on the socket while it gets free()ed.

Restored the (proven) 8.3 behavior of assigning these sockets after the two
connections are established.

Credits for reporting the issue are going to Arne Redlich.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_receiver.c

@@ -842,7 +842,7 @@ int drbd_connected(struct drbd_conf *mdev)
  */
 static int conn_connect(struct drbd_tconn *tconn)
 {
-	struct socket *sock, *msock;
+	struct drbd_socket sock, msock;
 	struct drbd_conf *mdev;
 	struct net_conf *nc;
 	int vnr, timeout, try, h, ok;
@@ -851,6 +851,15 @@ static int conn_connect(struct drbd_tconn *tconn)
 	if (conn_request_state(tconn, NS(conn, C_WF_CONNECTION), CS_VERBOSE) < SS_SUCCESS)
 		return -2;
 
+	mutex_init(&sock.mutex);
+	sock.sbuf = tconn->data.sbuf;
+	sock.rbuf = tconn->data.rbuf;
+	sock.socket = NULL;
+	mutex_init(&msock.mutex);
+	msock.sbuf = tconn->meta.sbuf;
+	msock.rbuf = tconn->meta.rbuf;
+	msock.socket = NULL;
+
 	clear_bit(DISCARD_CONCURRENT, &tconn->flags);
 
 	/* Assume that the peer only understands protocol 80 until we know better.  */
@@ -869,22 +878,26 @@ static int conn_connect(struct drbd_tconn *tconn)
 		}
 
 		if (s) {
-			if (!tconn->data.socket) {
-				tconn->data.socket = s;
-				send_first_packet(tconn, &tconn->data, P_INITIAL_DATA);
-			} else if (!tconn->meta.socket) {
-				tconn->meta.socket = s;
-				send_first_packet(tconn, &tconn->meta, P_INITIAL_META);
+			if (!sock.socket) {
+				sock.socket = s;
+				send_first_packet(tconn, &sock, P_INITIAL_DATA);
+			} else if (!msock.socket) {
+				msock.socket = s;
+				send_first_packet(tconn, &msock, P_INITIAL_META);
 			} else {
 				conn_err(tconn, "Logic error in conn_connect()\n");
 				goto out_release_sockets;
 			}
 		}
 
-		if (tconn->data.socket && tconn->meta.socket) {
-			schedule_timeout_interruptible(tconn->net_conf->ping_timeo*HZ/10);
-			ok = drbd_socket_okay(&tconn->data.socket);
-			ok = drbd_socket_okay(&tconn->meta.socket) && ok;
+		if (sock.socket && msock.socket) {
+			rcu_read_lock();
+			nc = rcu_dereference(tconn->net_conf);
+			timeout = nc->ping_timeo * HZ / 10;
+			rcu_read_unlock();
+			schedule_timeout_interruptible(timeout);
+			ok = drbd_socket_okay(&sock.socket);
+			ok = drbd_socket_okay(&msock.socket) && ok;
 			if (ok)
 				break;
 		}
@@ -893,22 +906,22 @@ retry:
 		s = drbd_wait_for_connect(tconn);
 		if (s) {
 			try = receive_first_packet(tconn, s);
-			drbd_socket_okay(&tconn->data.socket);
-			drbd_socket_okay(&tconn->meta.socket);
+			drbd_socket_okay(&sock.socket);
+			drbd_socket_okay(&msock.socket);
 			switch (try) {
 			case P_INITIAL_DATA:
-				if (tconn->data.socket) {
+				if (sock.socket) {
 					conn_warn(tconn, "initial packet S crossed\n");
-					sock_release(tconn->data.socket);
+					sock_release(sock.socket);
 				}
-				tconn->data.socket = s;
+				sock.socket = s;
 				break;
 			case P_INITIAL_META:
-				if (tconn->meta.socket) {
+				if (msock.socket) {
 					conn_warn(tconn, "initial packet M crossed\n");
-					sock_release(tconn->meta.socket);
+					sock_release(msock.socket);
 				}
-				tconn->meta.socket = s;
+				msock.socket = s;
 				set_bit(DISCARD_CONCURRENT, &tconn->flags);
 				break;
 			default:
@@ -928,49 +941,48 @@ retry:
 				goto out_release_sockets;
 		}
 
-		if (tconn->data.socket && &tconn->meta.socket) {
-			ok = drbd_socket_okay(&tconn->data.socket);
-			ok = drbd_socket_okay(&tconn->meta.socket) && ok;
+		if (sock.socket && &msock.socket) {
+			ok = drbd_socket_okay(&sock.socket);
+			ok = drbd_socket_okay(&msock.socket) && ok;
 			if (ok)
 				break;
 		}
 	} while (1);
 
-	sock  = tconn->data.socket;
-	msock = tconn->meta.socket;
+	sock.socket->sk->sk_reuse = 1; /* SO_REUSEADDR */
+	msock.socket->sk->sk_reuse = 1; /* SO_REUSEADDR */
 
-	msock->sk->sk_reuse = 1; /* SO_REUSEADDR */
-	sock->sk->sk_reuse = 1; /* SO_REUSEADDR */
+	sock.socket->sk->sk_allocation = GFP_NOIO;
+	msock.socket->sk->sk_allocation = GFP_NOIO;
 
-	sock->sk->sk_allocation = GFP_NOIO;
-	msock->sk->sk_allocation = GFP_NOIO;
-
-	sock->sk->sk_priority = TC_PRIO_INTERACTIVE_BULK;
-	msock->sk->sk_priority = TC_PRIO_INTERACTIVE;
+	sock.socket->sk->sk_priority = TC_PRIO_INTERACTIVE_BULK;
+	msock.socket->sk->sk_priority = TC_PRIO_INTERACTIVE;
 
 	/* NOT YET ...
-	 * sock->sk->sk_sndtimeo = tconn->net_conf->timeout*HZ/10;
-	 * sock->sk->sk_rcvtimeo = MAX_SCHEDULE_TIMEOUT;
+	 * sock.socket->sk->sk_sndtimeo = tconn->net_conf->timeout*HZ/10;
+	 * sock.socket->sk->sk_rcvtimeo = MAX_SCHEDULE_TIMEOUT;
 	 * first set it to the P_CONNECTION_FEATURES timeout,
 	 * which we set to 4x the configured ping_timeout. */
 	rcu_read_lock();
 	nc = rcu_dereference(tconn->net_conf);
 
-	sock->sk->sk_sndtimeo =
-	sock->sk->sk_rcvtimeo = nc->ping_timeo*4*HZ/10;
+	sock.socket->sk->sk_sndtimeo =
+	sock.socket->sk->sk_rcvtimeo = nc->ping_timeo*4*HZ/10;
 
-	msock->sk->sk_rcvtimeo = nc->ping_int*HZ;
+	msock.socket->sk->sk_rcvtimeo = nc->ping_int*HZ;
 	timeout = nc->timeout * HZ / 10;
 	discard_my_data = nc->discard_my_data;
 	rcu_read_unlock();
 
-	msock->sk->sk_sndtimeo = timeout;
+	msock.socket->sk->sk_sndtimeo = timeout;
 
 	/* we don't want delays.
 	 * we use TCP_CORK where appropriate, though */
-	drbd_tcp_nodelay(sock);
-	drbd_tcp_nodelay(msock);
+	drbd_tcp_nodelay(sock.socket);
+	drbd_tcp_nodelay(msock.socket);
 
+	tconn->data.socket = sock.socket;
+	tconn->meta.socket = msock.socket;
 	tconn->last_received = jiffies;
 
 	h = drbd_do_features(tconn);
@@ -989,8 +1001,8 @@ retry:
 		}
 	}
 
-	sock->sk->sk_sndtimeo = timeout;
-	sock->sk->sk_rcvtimeo = MAX_SCHEDULE_TIMEOUT;
+	tconn->data.socket->sk->sk_sndtimeo = timeout;
+	tconn->data.socket->sk->sk_rcvtimeo = MAX_SCHEDULE_TIMEOUT;
 
 	if (drbd_send_protocol(tconn) == -EOPNOTSUPP)
 		return -1;
@@ -1027,14 +1039,10 @@ retry:
 	return h;
 
 out_release_sockets:
-	if (tconn->data.socket) {
-		sock_release(tconn->data.socket);
-		tconn->data.socket = NULL;
-	}
-	if (tconn->meta.socket) {
-		sock_release(tconn->meta.socket);
-		tconn->meta.socket = NULL;
-	}
+	if (sock.socket)
+		sock_release(sock.socket);
+	if (msock.socket)
+		sock_release(msock.socket);
 	return -1;
 }