From 1d10b44546e2605b6dd8a006dcc0d03166649e2d Mon Sep 17 00:00:00 2001
From: Marcel Apfelbaum <marcel.a@redhat.com>
Date: Mon, 26 May 2014 15:40:55 +0300
Subject: [PATCH] qapi: Avoid output visitor crashing if it encounters a NULL
 value
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A NULL value is not added to visitor's stack, but there
is no check for that when the visitor tries to return
that value, leading to QEMU crash.

Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
---
 qapi/qmp-output-visitor.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c
index 74a5684ed3..96b338463e 100644
--- a/qapi/qmp-output-visitor.c
+++ b/qapi/qmp-output-visitor.c
@@ -66,6 +66,12 @@ static QObject *qmp_output_pop(QmpOutputVisitor *qov)
 static QObject *qmp_output_first(QmpOutputVisitor *qov)
 {
     QStackEntry *e = QTAILQ_LAST(&qov->stack, QStack);
+
+    /* FIXME - find a better way to deal with NULL values */
+    if (!e) {
+        return NULL;
+    }
+
     return e->value;
 }