qdev-monitor: fix segmentation fault on qdev_device_help()

Normally, qmp_device_list_properties() may return NULL when
a device haven't special properties excpet Object and DeviceState
properties, such as virtio-balloon-device.

We just need check local_err instead of prop_list.

Example:

Segmentation fault (core dumped)

The backtrace as below:

Program received signal SIGSEGV, Segmentation fault.
0x00005555559af1a8 in error_get_pretty (err=0x0) at util/error.c:152
152         return err->msg;
(gdb) bt
    func=0x55555574a6ca <device_help_func>, opaque=0x0, abort_on_failure=0) at util/qemu-option.c:1072

Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

diff --git a/qdev-monitor.c b/qdev-monitor.c
index fb9ee24..5ec6606 100644 (file)
--- a/qdev-monitor.c
+++ b/qdev-monitor.c
@@ -206,7 +206,7 @@ int qdev_device_help(QemuOpts *opts)
     }
 
     prop_list = qmp_device_list_properties(driver, &local_err);
-    if (!prop_list) {
+    if (local_err) {
         error_printf("%s\n", error_get_pretty(local_err));
         error_free(local_err);
         return 1;