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qapi: fix double free in qmp_output_visitor_cleanup()

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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>
This commit is contained in:
Laszlo Ersek 2012-03-20 11:22:48 +01:00 committed by Luiz Capitulino
parent 8a22565b7c
commit f24582d6ad
1 changed files with 5 additions and 3 deletions
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8
qapi/qmp-output-visitor.c
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@ -199,14 +199,16 @@ void qmp_output_visitor_cleanup(QmpOutputVisitor *v)
{
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);
}