From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:38157) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S8dRl-0006M8-QO for qemu-devel@nongnu.org; Fri, 16 Mar 2012 16:08:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S8dRj-0004N4-Mo for qemu-devel@nongnu.org; Fri, 16 Mar 2012 16:08:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36459) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S8dRj-0004Mu-En for qemu-devel@nongnu.org; Fri, 16 Mar 2012 16:08:19 -0400 From: Laszlo Ersek Date: Fri, 16 Mar 2012 20:16:12 +0100 Message-Id: <1331925372-5429-1-git-send-email-lersek@redhat.com> In-Reply-To: <20120316170056.GA24953@illuin> References: <20120316170056.GA24953@illuin> Subject: [Qemu-devel] [PATCH] qmp_output_visitor_cleanup(): fix double free List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, pbonzini@redhat.com, lcapitulino@redhat.com, jcody@redhat.com, aliguori@us.ibm.com, mdroth@linux.vnet.ibm.com, lersek@redhat.com 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 --- qapi/qmp-output-visitor.c | 8 +++++--- 1 files changed, 5 insertions(+), 3 deletions(-) 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 @@ 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); } -- 1.7.1