Re: [PATCH for-5.0] xen-block: Fix uninitialized variable

[Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>]

On 4/6/20 6:42 PM, Anthony PERARD wrote:
> Since 7f5d9b206d1e ("object-add: don't create return value if
> failed"), qmp_object_add() don't write any value in 'ret_data', thus
> has random data. Then qobject_unref() fails and abort().
>
> Fix by initialising 'ret_data' properly.
Or move qobject_unref() after the error check?

-- >8 --
diff --git a/hw/block/xen-block.c b/hw/block/xen-block.c
index 07bb32e22b..f3f1cbef65 100644
--- a/hw/block/xen-block.c
+++ b/hw/block/xen-block.c
@@ -869,7 +869,6 @@ static XenBlockIOThread 
*xen_block_iothread_create(const char *id,
     qdict_put_str(opts, "id", id);
     qmp_object_add(opts, &ret_data, &local_err);
     qobject_unref(opts);
-    qobject_unref(ret_data);

     if (local_err) {
         error_propagate(errp, local_err);
@@ -878,6 +877,7 @@ static XenBlockIOThread 
*xen_block_iothread_create(const char *id,
         g_free(iothread);
         return NULL;
     }
+    qobject_unref(ret_data);

     return iothread;
 }
---

> Fixes: 5f07c4d60d09 ("qapi: Flatten object-add")
> Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> ---
>   hw/block/xen-block.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/block/xen-block.c b/hw/block/xen-block.c
> index 07bb32e22b51..99cb4c67cb09 100644
> --- a/hw/block/xen-block.c
> +++ b/hw/block/xen-block.c
> @@ -860,7 +860,7 @@ static XenBlockIOThread *xen_block_iothread_create(const 
> char *id,
>       XenBlockIOThread *iothread = g_new(XenBlockIOThread, 1);
>       Error *local_err = NULL;
>       QDict *opts;
> -    QObject *ret_data;
> +    QObject *ret_data = NULL;
>   
>       iothread->id = g_strdup(id);
>