[Qemu-devel] [PATCH] qom: In function object_set_link_property(), first call object_ref(), then object_unref().

[alexander_barabash]

From: Alexander Barabash <address@hidden>

In the old implementation, if the new value of the property links
to the same object, as the old value, that object is first unref-ed,
and then ref-ed. This leads to unintended deinitialization of that object.

In the new implementation, this is fixed.

Signed-off-by: Alexander Barabash <address@hidden>
---
 qom/object.c |   18 +++++++++++++-----
 1 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/qom/object.c b/qom/object.c
index 941c291..d1b3ac7 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -892,19 +892,19 @@ static void object_set_link_property(Object *obj, Visitor 
*v, void *opaque,
                                      const char *name, Error **errp)
 {
     Object **child = opaque;
+    Object *old_target;
     bool ambiguous = false;
     const char *type;
     char *path;
     gchar *target_type;
+    bool clear_old_target = true;
 
     type = object_property_get_type(obj, name, NULL);
 
     visit_type_str(v, &path, name, errp);
 
-    if (*child) {
-        object_unref(*child);
-        *child = NULL;
-    }
+    old_target = *child;
+    *child = NULL;
 
     if (strcmp(path, "") != 0) {
         Object *target;
@@ -916,7 +916,11 @@ static void object_set_link_property(Object *obj, Visitor 
*v, void *opaque,
         if (ambiguous) {
             error_set(errp, QERR_AMBIGUOUS_PATH, path);
         } else if (target) {
-            object_ref(target);
+            if (target != old_target) {
+                object_ref(target);
+            } else {
+                clear_old_target = false;
+            }
             *child = target;
         } else {
             target = object_resolve_path(path, &ambiguous);
@@ -930,6 +934,10 @@ static void object_set_link_property(Object *obj, Visitor 
*v, void *opaque,
     }
 
     g_free(path);
+
+    if (clear_old_target && (old_target != NULL)) {
+        object_unref(old_target);
+    }
 }
 
 void object_property_add_link(Object *obj, const char *name,
-- 
1.7.5.4