object: fix OBJ_PROP_LINK_UNREF_ON_RELEASE ambivalence

A link property can be set during creation, with
object_property_add_link() and later with object_property_set_link().

add_link() doesn't add a reference to the target object, while
set_link() does.

Furthemore, OBJ_PROP_LINK_UNREF_ON_RELEASE flags, set during add_link,
says whether a reference must be released when the property is destroyed.
This can lead to leaks if the property was later set_link(), as the
added reference is never released.

Instead, rename OBJ_PROP_LINK_UNREF_ON_RELEASE to OBJ_PROP_LINK_STRONG
and use that has an indication on how the link handle reference
management in set_link().

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20180531195119.22021-3-marcandre.lureau@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/qom/object.c b/qom/object.c
index cb7a8cd589..e6462f289c 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1564,9 +1564,11 @@ static void object_set_link_property(Object *obj, Visitor *v,
         return;
     }
 
-    object_ref(new_target);
     *child = new_target;
-    object_unref(old_target);
+    if (prop->flags == OBJ_PROP_LINK_STRONG) {
+        object_ref(new_target);
+        object_unref(old_target);
+    }
 }
 
 static Object *object_resolve_link_property(Object *parent, void *opaque, const gchar *part)
@@ -1581,7 +1583,7 @@ static void object_release_link_property(Object *obj, const char *name,
 {
     LinkProperty *prop = opaque;
 
-    if ((prop->flags & OBJ_PROP_LINK_UNREF_ON_RELEASE) && *prop->child) {
+    if ((prop->flags & OBJ_PROP_LINK_STRONG) && *prop->child) {
         object_unref(*prop->child);
     }
     g_free(prop);