qom: Check for wellformed id in user_creatable_add_type()

Most code paths for creating a user creatable object go through
QemuOpts, which ensures that the provided 'id' option is actually a
valid identifier.

However, there are some code paths that don't go through QemuOpts:
qemu-storage-daemon --object (since commit 8db1efd) and QMP object-add
(since it was first introduced in commit cff8b2c). We need to have the
same validity check for those, too.

This adds the check and makes it print the same error message as
QemuOpts on failure.

Signed-off-by: Kevin Wolf <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

qom/object_interfaces.c

@@ -8,6 +8,7 @@
 #include "qapi/qobject-input-visitor.h"
 #include "qom/object_interfaces.h"
 #include "qemu/help_option.h"
+#include "qemu/id.h"
 #include "qemu/module.h"
 #include "qemu/option.h"
 #include "qapi/opts-visitor.h"
@@ -41,11 +42,19 @@ Object *user_creatable_add_type(const char *type, const char *id,
                                 const QDict *qdict,
                                 Visitor *v, Error **errp)
 {
+    ERRP_GUARD();
     Object *obj;
     ObjectClass *klass;
     const QDictEntry *e;
     Error *local_err = NULL;
 
+    if (id != NULL && !id_wellformed(id)) {
+        error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "id", "an identifier");
+        error_append_hint(errp, "Identifiers consist of letters, digits, "
+                          "'-', '.', '_', starting with a letter.\n");
+        return NULL;
+    }
+
     klass = object_class_by_name(type);
     if (!klass) {
         error_setg(errp, "invalid object type: %s", type);