On 04/16/2014 01:39 PM, Eduardo Habkost wrote:
> Currently it is very easy to crash QEMU by issuing an object-add command
> using an abstract class or a class that doesn't support
> TYPE_USER_CREATABLE as parameter.
>
> Example: with the following QMP command:
>
> (QEMU) object-add qom-type=cpu id=foo
>
> QEMU aborts at:
>
> ERROR:qom/object.c:335:object_initialize_with_type: assertion failed:
> (type->abstract == false)
>
> This patch moves the check for TYPE_USER_CREATABLE before object_new(),
> and adds a check to prevent the code from trying to instantiate abstract
> classes.
>
> Signed-off-by: Eduardo Habkost <ehabk...@redhat.com>
> ---
> Changes v2:
> * Change ordering: first check for TYPE_USER_CREATABLE and then check
> if class is abstract. This makes the ordering of checks closer to
> what's already done on device_add.
Changes look fine to me, re-tested to verify.
Reviewed-by: Matthew Rosato <mjros...@linux.vnet.ibm.com>
Tested-by: Matthew Rosato <mjros...@linux.vnet.ibm.com>
> ---
> qmp.c | 21 ++++++++++++++-------
> 1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/qmp.c b/qmp.c
> index 87a28f7..9a93ab1 100644
> --- a/qmp.c
> +++ b/qmp.c
> @@ -540,14 +540,27 @@ void object_add(const char *type, const char *id, const
> QDict *qdict,
> Visitor *v, Error **errp)
> {
> Object *obj;
> + ObjectClass *klass;
> const QDictEntry *e;
> Error *local_err = NULL;
>
> - if (!object_class_by_name(type)) {
> + klass = object_class_by_name(type);
> + if (!klass) {
> error_setg(errp, "invalid class name");
> return;
> }
>
> + if (!object_class_dynamic_cast(klass, TYPE_USER_CREATABLE)) {
> + error_setg(errp, "object type '%s' isn't supported by object-add",
> + type);
> + return;
> + }
> +
> + if (object_class_is_abstract(klass)) {
> + error_setg(errp, "object type '%s' is abstract", type);
> + return;
> + }
> +
> obj = object_new(type);
> if (qdict) {
> for (e = qdict_first(qdict); e; e = qdict_next(qdict, e)) {
> @@ -558,12 +571,6 @@ void object_add(const char *type, const char *id, const
> QDict *qdict,
> }
> }
>
> - if (!object_dynamic_cast(obj, TYPE_USER_CREATABLE)) {
> - error_setg(&local_err, "object type '%s' isn't supported by
> object-add",
> - type);
> - goto out;
> - }
> -
> user_creatable_complete(obj, &local_err);
> if (local_err) {
> goto out;
>
