[Qemu-stable] [PATCH] qdev: fix crash by validating the object type

[Amos Kong]

QEMU crashed when I try to list device parameters, the driver name is
actually the available bus name.

 # qemu -device virtio-pci-bus,?
 # qemu -device virtio-bus,?
 # qemu -device virtio-serial-bus,?
 qdev-monitor.c:212:qdev_device_help: Object 0x7fd932f50620 is not an
 instance of type device
 Aborted (core dumped)

We can also reproduce this bug by adding device from monitor, so it's
worth to fix the crash.

 (qemu) device_add virtio-serial-bus
 qdev-monitor.c:491:qdev_device_add: Object 0x7f5e89530920 is not an
 instance of type device
 Aborted (core dumped)

Cc: address@hidden
Signed-off-by: Amos Kong <address@hidden>
---
 qdev-monitor.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/qdev-monitor.c b/qdev-monitor.c
index 9268c87..40c117d 100644
--- a/qdev-monitor.c
+++ b/qdev-monitor.c
@@ -206,7 +206,7 @@ int qdev_device_help(QemuOpts *opts)
         }
     }
 
-    if (!klass) {
+    if (!object_class_dynamic_cast(klass, TYPE_DEVICE)) {
         return 0;
     }
     do {
-- 
1.9.0