From 56a6f02b8ce1fe41a2a9077593e46eca7d98267d Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Thu, 28 Apr 2016 15:45:26 -0600 Subject: [PATCH] qmp: Tighten output visitor rules Tighten assertions in the QMP output visitor, so that: - qmp_output_get_qobject() can only be called after pairing a visit_end_* for every visit_start_* (rather than allowing it on a partially built object) - qmp_output_get_qobject() cannot be called unless at least one visit_type_* or visit_start/visit_end pair has occurred since creation/reset (the accidental return of NULL fixed by commit ab8bf1d7 would have been much easier to diagnose) - ensure that we are encountering the expected object or list type, to provide protection against mismatched push(struct)/ pop(list) or push(list)/pop(struct), similar to the qmp-input protection added in commit bdd8e6b5. - ensure that except for the root, 'name' is non-null inside a dict, and NULL inside a list (this may need changing later if we add "name.0" support for better error messages for a list, but for now it makes sure all users are at least consistent) Signed-off-by: Eric Blake Message-Id: <1461879932-9020-19-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster --- qapi/qmp-output-visitor.c | 30 +++++++++++++++--------------- 1 file changed, 15 insertions(+), 15 deletions(-) diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c index 5681ad3471..4e21f1ddf0 100644 --- a/qapi/qmp-output-visitor.c +++ b/qapi/qmp-output-visitor.c @@ -82,9 +82,8 @@ static void qmp_output_add_obj(QmpOutputVisitor *qov, const char *name, QObject *cur = e ? e->value : NULL; if (!cur) { - /* FIXME we should require the user to reset the visitor, rather - * than throwing away the previous root */ - qobject_decref(qov->root); + /* Don't allow reuse of visitor on more than one root */ + assert(!qov->root); qov->root = value; } else { switch (qobject_type(cur)) { @@ -93,6 +92,7 @@ static void qmp_output_add_obj(QmpOutputVisitor *qov, const char *name, qdict_put_obj(qobject_to_qdict(cur), name, value); break; case QTYPE_QLIST: + assert(!name); qlist_append_obj(qobject_to_qlist(cur), value); break; default: @@ -114,7 +114,8 @@ static void qmp_output_start_struct(Visitor *v, const char *name, void **obj, static void qmp_output_end_struct(Visitor *v, Error **errp) { QmpOutputVisitor *qov = to_qov(v); - qmp_output_pop(qov); + QObject *value = qmp_output_pop(qov); + assert(qobject_type(value) == QTYPE_QDICT); } static void qmp_output_start_list(Visitor *v, const char *name, Error **errp) @@ -145,7 +146,8 @@ static GenericList *qmp_output_next_list(Visitor *v, GenericList **listp, static void qmp_output_end_list(Visitor *v) { QmpOutputVisitor *qov = to_qov(v); - qmp_output_pop(qov); + QObject *value = qmp_output_pop(qov); + assert(qobject_type(value) == QTYPE_QLIST); } static void qmp_output_type_int64(Visitor *v, const char *name, int64_t *obj, @@ -202,18 +204,16 @@ static void qmp_output_type_null(Visitor *v, const char *name, Error **errp) qmp_output_add_obj(qov, name, qnull()); } -/* Finish building, and return the root object. Will not be NULL. */ +/* Finish building, and return the root object. + * The root object is never null. The caller becomes the object's + * owner, and should use qobject_decref() when done with it. */ QObject *qmp_output_get_qobject(QmpOutputVisitor *qov) { - /* FIXME: we should require that a visit occurred, and that it is - * complete (no starts without a matching end) */ - QObject *obj = qov->root; - if (obj) { - qobject_incref(obj); - } else { - obj = qnull(); - } - return obj; + /* A visit must have occurred, with each start paired with end. */ + assert(qov->root && QTAILQ_EMPTY(&qov->stack)); + + qobject_incref(qov->root); + return qov->root; } Visitor *qmp_output_get_visitor(QmpOutputVisitor *v) -- 2.11.0