qapi: fix double free in qmp_output_visitor_cleanup()
Stack entries in QmpOutputVisitor are navigation links (weak references),
except the bottom (ie. least recently added) entry, which owns the root
QObject [1]. Make qmp_output_visitor_cleanup() drop the stack entries,
then release the QObject tree by the root.
Attempting to serialize an invalid enum inside a dictionary is an example
for triggering the double free.
[1] http://lists.nongnu.org/archive/html/qemu-devel/2012-03/msg03276.html
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c
index e0697b0..2bce9d5 100644
--- a/qapi/qmp-output-visitor.c
+++ b/qapi/qmp-output-visitor.c
@@ -199,14 +199,16 @@
{
QStackEntry *e, *tmp;
+ /* The bottom QStackEntry, if any, owns the root QObject. See the
+ * qmp_output_push_obj() invocations in qmp_output_add_obj(). */
+ QObject *root = QTAILQ_EMPTY(&v->stack) ? NULL : qmp_output_first(v);
+
QTAILQ_FOREACH_SAFE(e, &v->stack, node, tmp) {
QTAILQ_REMOVE(&v->stack, e, node);
- if (e->value) {
- qobject_decref(e->value);
- }
g_free(e);
}
+ qobject_decref(root);
g_free(v);
}