[gtk-vnc] Avoid crash if attempt to connect to an invalid host or port

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

commit c61d47c7e25110073395458cb92d87e53489850a
Author: Christophe Fergeau <cfergeau redhat com>
Date:   Fri Dec 9 16:09:41 2016 +0100

    Avoid crash if attempt to connect to an invalid host or port
    
    If vnc_display_open_host() is called with a NULL port or host,
    vnc_connection_open_host_internal() will eventually crash.
    This commits adds runtime checks to return early with
    g_return_val_if_fail() when this happens rather than
    crashing
    
     #0  0x00007ffff37de3d3 in __strchr_sse2 () at ../sysdeps/x86_64/strchr.S:32
     #1  0x00007ffff4661a17 in g_inet_socket_address_new_from_string (address=0x0, port=0)
         at ginetsocketaddress.c:416
     #2  0x00007ffff466b784 in g_network_address_parse_sockaddr (addr=addr@entry=0x969f50 [GNetworkAddress])
         at gnetworkaddress.c:245
     #3  0x00007ffff466ba94 in g_network_address_address_enumerator_next (enumerator=0x972ca0 
[GNetworkAddressAddressEnumerator], cancellable=0x0, error=<optimized out>) at gnetworkaddress.c:919
     #4  0x00007ffff727130b in vnc_connection_open_host_internal (conn=0x99bbf0 [VncConnection])
         at vncconnection.c:5395
     #5  0x00007ffff7271523 in vnc_connection_coroutine (opaque=0x99bbf0) at vncconnection.c:5448
     #6  0x00007ffff7272e54 in coroutine_trampoline (cc=0x998080) at coroutine_ucontext.c:55
     #7  0x00007ffff7272b65 in continuation_trampoline (i0=10059904, i1=0) at continuation.c:43
     #8  0x00007ffff379dc00 in __start_context () at /lib64/libc.so.6
     #9  0x0000000000998448 in  ()
     #10 0x0000000000000000 in  ()

 src/vncconnection.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/src/vncconnection.c b/src/vncconnection.c
index 8a52346..61f74b4 100644
--- a/src/vncconnection.c
+++ b/src/vncconnection.c
@@ -5425,6 +5425,8 @@ static gboolean vnc_connection_open_host_internal(VncConnection *conn)
 
     VNC_DEBUG("Resolving host %s %s", priv->host, priv->port);
 
+    g_return_val_if_fail((priv->host != NULL) && (port != 0), FALSE);
+
     addr = g_network_address_new(priv->host, port);
 
     enumerator = g_socket_connectable_enumerate (addr);