[gtk-vnc] Avoid crash in TLS cleanup code on shutdown

[Daniel P. Berrange <dberrange src gnome org>]

commit 5760a2a28d85cb79e39063cfd8ee8aee975caf24
Author: Daniel P. Berrange <dan berrange com>
Date:   Mon Nov 22 21:44:56 2010 +0000

    Avoid crash in TLS cleanup code on shutdown
    
    The gnutls_bye() method may try to send data on the socket todo
    graceful TLS shutdown. The priv->sock variable is possibly
    already NULL at this point if the close was triggered via the
    vnc_connection_shutdown() method. Change the latter so that
    it only calls g_socket_close, not actually free'ing the
    priv->sock object immediately. Also put sanity check code in
    the TLS push/pull functions to catch future bugs in this area

 src/vncconnection.c |   21 +++++++++++++++++----
 1 files changed, 17 insertions(+), 4 deletions(-)
---
diff --git a/src/vncconnection.c b/src/vncconnection.c
index 4a0c53c..433256a 100644
--- a/src/vncconnection.c
+++ b/src/vncconnection.c
@@ -939,6 +939,12 @@ static ssize_t vnc_connection_tls_push(gnutls_transport_ptr_t transport,
 	int ret;
 	GError *error = NULL;
 
+	if (!priv->sock) {
+		VNC_DEBUG("Unexpected TLS push on closed socket");
+		errno = EBADF;
+		return -1;
+	}
+
 	ret = g_socket_send(priv->sock, data, len, NULL, &error);
 	if (ret < 0) {
 		if (error) {
@@ -962,6 +968,12 @@ static ssize_t vnc_connection_tls_pull(gnutls_transport_ptr_t transport,
 	int ret;
 	GError *error = NULL;
 
+	if (!priv->sock) {
+		VNC_DEBUG("Unexpected TLS pull on closed socket");
+		errno = EBADF;
+		return -1;
+	}
+
 	ret = g_socket_receive(priv->sock, data, len, NULL, &error);
 	if (ret < 0) {
 		if (error) {
@@ -4461,11 +4473,12 @@ void vnc_connection_shutdown(VncConnection *conn)
 	VNC_DEBUG("Waking up couroutine to shutdown gracefully");
 	g_io_wakeup(&priv->wait);
 
-	if (priv->sock) {
+	/* Closing the socket triggers an I/O error in the
+	 * event loop resulting...eventually.. in a call
+	 * to vnc_connection_close for full cleanup
+	 */
+	if (priv->sock)
 		g_socket_close(priv->sock, NULL);
-		g_object_unref(priv->sock);
-		priv->sock = NULL;
-	}
 }
 
 gboolean vnc_connection_is_open(VncConnection *conn)