[gupnp] Avoid a crash in gupnp_root_device_constructor()

[Jens Georg <jensgeorg src gnome org>]

commit 47c1514285d1229533c9c0e933f6a627db02f3f4
Author: Sven Neumann <neumann teufel de>
Date:   Tue Mar 28 09:39:54 2017 +0200

    Avoid a crash in gupnp_root_device_constructor()
    
    The network interface used by GUPnPContext might not be usable
    at the point where gupnp_root_device_constructor() is run, which
    resulted in warnings and a crash when the code tried to use a
    SoupURI pointer that was NULL.
    
    Handle this by letting the GUPnPRootDevice construction fail.
    
    Signed-off-by: Sven Neumann <neumann teufel de>
    
    https://bugzilla.gnome.org/show_bug.cgi?id=780640

 libgupnp/gupnp-context.c     |    5 ++++-
 libgupnp/gupnp-error.h       |    2 ++
 libgupnp/gupnp-root-device.c |   14 ++++++++++++--
 3 files changed, 18 insertions(+), 3 deletions(-)
---
diff --git a/libgupnp/gupnp-context.c b/libgupnp/gupnp-context.c
index 6296684..47a5cb6 100644
--- a/libgupnp/gupnp-context.c
+++ b/libgupnp/gupnp-context.c
@@ -628,7 +628,10 @@ _gupnp_context_get_server_uri (GUPnPContext *context)
         if (context->priv->server_uri == NULL)
                 context->priv->server_uri = make_server_uri (context);
 
-        return soup_uri_copy (context->priv->server_uri);
+        if (context->priv->server_uri)
+                return soup_uri_copy (context->priv->server_uri);
+
+        return NULL;
 }
 
 /**
diff --git a/libgupnp/gupnp-error.h b/libgupnp/gupnp-error.h
index ba0bfb0..3816492 100644
--- a/libgupnp/gupnp-error.h
+++ b/libgupnp/gupnp-error.h
@@ -128,6 +128,7 @@ gupnp_rootdevice_error_quark (void) G_GNUC_CONST;
  * @GUPNP_ROOT_DEVICE_ERROR_NO_CONTEXT: No #GUPnPContext was passed to the root device.
  * @GUPNP_ROOT_DEVICE_ERROR_NO_DESCRIPTION_PATH: Device description path was missing
  * @GUPNP_ROOT_DEVICE_ERROR_NO_DESCRIPTION_FOLDER: Description folder was missing
+ * @GUPNP_ROOT_DEVICE_ERROR_NO_NETWORK: Network interface is not usable
  *
  * #GError codes used for errors during #GUPnPRootDevice creation
  */
@@ -135,6 +136,7 @@ typedef enum {
         GUPNP_ROOT_DEVICE_ERROR_NO_CONTEXT,
         GUPNP_ROOT_DEVICE_ERROR_NO_DESCRIPTION_PATH,
         GUPNP_ROOT_DEVICE_ERROR_NO_DESCRIPTION_FOLDER,
+        GUPNP_ROOT_DEVICE_ERROR_NO_NETWORK,
         GUPNP_ROOT_DEVICE_ERROR_FAIL
 } GUPnPRootdeviceError;
 
diff --git a/libgupnp/gupnp-root-device.c b/libgupnp/gupnp-root-device.c
index 55a2740..4112e94 100644
--- a/libgupnp/gupnp-root-device.c
+++ b/libgupnp/gupnp-root-device.c
@@ -333,6 +333,15 @@ gupnp_root_device_initable_init (GInitable     *initable,
                 return FALSE;
         }
 
+        uri = _gupnp_context_get_server_uri (context);
+        if (uri == NULL) {
+                g_set_error_literal (error,
+                                     GUPNP_ROOT_DEVICE_ERROR,
+                                     GUPNP_ROOT_DEVICE_ERROR_NO_NETWORK,
+                                     "Network interface is not usable");
+
+                return FALSE;
+        }
 
         if (g_path_is_absolute (device->priv->description_path))
                 desc_path = g_strdup (device->priv->description_path);
@@ -401,10 +410,8 @@ gupnp_root_device_initable_init (GInitable     *initable,
         gupnp_context_host_path (context, device->priv->description_dir, "");
 
         /* Generate full location */
-        uri = _gupnp_context_get_server_uri (context);
         soup_uri_set_path (uri, relative_location);
         location = soup_uri_to_string (uri, FALSE);
-        soup_uri_free (uri);
 
         g_free (relative_location);
 
@@ -440,6 +447,9 @@ gupnp_root_device_initable_init (GInitable     *initable,
 
  DONE:
         /* Cleanup */
+        if (uri)
+                soup_uri_free (uri);
+
         g_free (desc_path);
         g_free (location);