Re: [Qemu-devel] [PATCH v2 3/4] qapi: return a 'missing parameter' error

[Marc-André Lureau]

Hi

----- Original Message -----
> Marc-André Lureau <address@hidden> writes:
> 
> > The 'old' dispatch code returned a QERR_MISSING_PARAMETER for missing
> > parameters, but the qapi qmp_dispatch() code uses
> > QERR_INVALID_PARAMETER_TYPE.
> >
> > Improve qapi code to return QERR_INVALID_PARAMETER_TYPE where
> > appropriate.
> >
> > Signed-off-by: Marc-André Lureau <address@hidden>
> > Reviewed-by: Alberto Garcia <address@hidden>
> > ---
> >  qapi/qmp-input-visitor.c | 73
> >  +++++++++++++++++++++++++++++++++++++-----------
> >  1 file changed, 56 insertions(+), 17 deletions(-)
> >
> > diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c
> > index c1019d6..6f85664 100644
> > --- a/qapi/qmp-input-visitor.c
> > +++ b/qapi/qmp-input-visitor.c
> > @@ -56,7 +56,7 @@ static QmpInputVisitor *to_qiv(Visitor *v)
> >  
> >  static QObject *qmp_input_get_object(QmpInputVisitor *qiv,
> >                                       const char *name,
> > -                                     bool consume)
> > +                                     bool consume, Error **errp)
> >  {
> >      StackObject *tos;
> >      QObject *qobj;
> > @@ -80,6 +80,9 @@ static QObject *qmp_input_get_object(QmpInputVisitor
> > *qiv,
> >              bool removed = g_hash_table_remove(tos->h, name);
> >              assert(removed);
> >          }
> > +        if (!ret) {
> > +            error_setg(errp, QERR_MISSING_PARAMETER, name);
> > +        }
> >      } else {
> >          assert(qobject_type(qobj) == QTYPE_QLIST);
> >          assert(!name);
> > @@ -165,13 +168,16 @@ static void qmp_input_start_struct(Visitor *v, const
> > char *name, void **obj,
> >                                     size_t size, Error **errp)
> >  {
> >      QmpInputVisitor *qiv = to_qiv(v);
> > -    QObject *qobj = qmp_input_get_object(qiv, name, true);
> > +    QObject *qobj = qmp_input_get_object(qiv, name, true, errp);
> >      Error *err = NULL;
> >  
> >      if (obj) {
> >          *obj = NULL;
> >      }
> > -    if (!qobj || qobject_type(qobj) != QTYPE_QDICT) {
> > +    if (!qobj) {
> > +        return;
> > +    }
> > +    if (qobject_type(qobj) != QTYPE_QDICT) {
> >          error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name :
> >          "null",
> >                     "QDict");
> >          return;
> > @@ -193,10 +199,13 @@ static void qmp_input_start_list(Visitor *v, const
> > char *name,
> >                                   GenericList **list, size_t size, Error
> >                                   **errp)
> >  {
> >      QmpInputVisitor *qiv = to_qiv(v);
> > -    QObject *qobj = qmp_input_get_object(qiv, name, true);
> > +    QObject *qobj = qmp_input_get_object(qiv, name, true, errp);
> >      const QListEntry *entry;
> >  
> > -    if (!qobj || qobject_type(qobj) != QTYPE_QLIST) {
> > +    if (!qobj) {
> > +        return;
> > +    }
> > +    if (qobject_type(qobj) != QTYPE_QLIST) {
> >          if (list) {
> >              *list = NULL;
> >          }
> > @@ -234,11 +243,10 @@ static void qmp_input_start_alternate(Visitor *v,
> > const char *name,
> >                                        bool promote_int, Error **errp)
> >  {
> >      QmpInputVisitor *qiv = to_qiv(v);
> > -    QObject *qobj = qmp_input_get_object(qiv, name, false);
> > +    QObject *qobj = qmp_input_get_object(qiv, name, false, errp);
> >  
> > +    *obj = NULL;
> >      if (!qobj) {
> > -        *obj = NULL;
> > -        error_setg(errp, QERR_MISSING_PARAMETER, name ? name : "null");
> >          return;
> >      }
> >      *obj = g_malloc0(size);
> 
> The patch does more than one thing: in addition to fixing the 'missing
> parameter' regression, it also messes with *obj = NULL in places.  These
> changes may well make sense, but they should be a separate patch, to
> ease review.

Looking more at it, I think we can leave it only in the error case.

> 
> > @@ -252,8 +260,13 @@ static void qmp_input_type_int64(Visitor *v, const
> > char *name, int64_t *obj,
> >                                   Error **errp)
> >  {
> >      QmpInputVisitor *qiv = to_qiv(v);
> > -    QInt *qint = qobject_to_qint(qmp_input_get_object(qiv, name, true));
> > +    QObject *qobj = qmp_input_get_object(qiv, name, true, errp);
> > +    QInt *qint;
> >  
> > +    if (!qobj) {
> > +        return;
> > +    }
> > +    qint = qobject_to_qint(qobj);
> >      if (!qint) {
> >          error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name :
> >          "null",
> >                     "integer");
> > @@ -268,8 +281,13 @@ static void qmp_input_type_uint64(Visitor *v, const
> > char *name, uint64_t *obj,
> >  {
> >      /* FIXME: qobject_to_qint mishandles values over INT64_MAX */
> >      QmpInputVisitor *qiv = to_qiv(v);
> > -    QInt *qint = qobject_to_qint(qmp_input_get_object(qiv, name, true));
> > +    QObject *qobj = qmp_input_get_object(qiv, name, true, errp);
> > +    QInt *qint;
> >  
> > +    if (!qobj) {
> > +        return;
> > +    }
> > +    qint = qobject_to_qint(qobj);
> >      if (!qint) {
> >          error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name :
> >          "null",
> >                     "integer");
> > @@ -283,8 +301,13 @@ static void qmp_input_type_bool(Visitor *v, const char
> > *name, bool *obj,
> >                                  Error **errp)
> >  {
> >      QmpInputVisitor *qiv = to_qiv(v);
> > -    QBool *qbool = qobject_to_qbool(qmp_input_get_object(qiv, name,
> > true));
> > +    QObject *qobj = qmp_input_get_object(qiv, name, true, errp);
> > +    QBool *qbool;
> >  
> > +    if (!qobj) {
> > +        return;
> > +    }
> > +    qbool = qobject_to_qbool(qobj);
> >      if (!qbool) {
> >          error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name :
> >          "null",
> >                     "boolean");
> > @@ -298,10 +321,15 @@ static void qmp_input_type_str(Visitor *v, const char
> > *name, char **obj,
> >                                 Error **errp)
> >  {
> >      QmpInputVisitor *qiv = to_qiv(v);
> > -    QString *qstr = qobject_to_qstring(qmp_input_get_object(qiv, name,
> > true));
> > +    QObject *qobj = qmp_input_get_object(qiv, name, true, errp);
> > +    QString *qstr;
> >  
> > +    *obj = NULL;
> > +    if (!qobj) {
> > +        return;
> > +    }
> > +    qstr = qobject_to_qstring(qobj);
> >      if (!qstr) {
> > -        *obj = NULL;
> >          error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name :
> >          "null",
> >                     "string");
> >          return;
> > @@ -314,10 +342,13 @@ static void qmp_input_type_number(Visitor *v, const
> > char *name, double *obj,
> >                                    Error **errp)
> >  {
> >      QmpInputVisitor *qiv = to_qiv(v);
> > -    QObject *qobj = qmp_input_get_object(qiv, name, true);
> > +    QObject *qobj = qmp_input_get_object(qiv, name, true, errp);
> >      QInt *qint;
> >      QFloat *qfloat;
> >  
> > +    if (!qobj) {
> > +        return;
> > +    }
> >      qint = qobject_to_qint(qobj);
> >      if (qint) {
> >          *obj = qint_get_int(qobject_to_qint(qobj));
> > @@ -338,7 +369,12 @@ static void qmp_input_type_any(Visitor *v, const char
> > *name, QObject **obj,
> >                                 Error **errp)
> >  {
> >      QmpInputVisitor *qiv = to_qiv(v);
> > -    QObject *qobj = qmp_input_get_object(qiv, name, true);
> > +    QObject *qobj = qmp_input_get_object(qiv, name, true, errp);
> > +
> > +    *obj = NULL;
> > +    if (!qobj) {
> > +        return;
> > +    }
> >  
> >      qobject_incref(qobj);
> >      *obj = qobj;
> 
> The patch does a third thing: it fixes a crash bug.  The old code fails
> to fail when the parameter doesn't exist.  Instead, it sets *obj = NULL,
> violating its contract.  Reproducer:
> 
>     { "execute": "qom-set",
>       "arguments": { "path": "/machine", "property": "rtc-time" } }
> 
> Separate patch, please, cc: qemu-stable.
> 

We can make it a seperate patch, but we still need to return an error, that's 
what this patch does.

A seperate patch will look like:

@@ -338,6 +338,12 @@ static void qmp_input_type_any(Visitor *v, const char 
*name, QObject **obj,
     QmpInputVisitor *qiv = to_qiv(v);
     QObject *qobj = qmp_input_get_object(qiv, name, true);
 
+    if (!qobj) {
+        error_setg(errp, QERR_MISSING_PARAMETER, name ? name : "null");
+        *obj = NULL;
+        return;
+    }

I think we may as well just take this patch, what do you think?


> > @@ -347,8 +383,11 @@ static void qmp_input_type_any(Visitor *v, const char
> > *name, QObject **obj,
> >  static void qmp_input_type_null(Visitor *v, const char *name, Error
> >  **errp)
> >  {
> >      QmpInputVisitor *qiv = to_qiv(v);
> > -    QObject *qobj = qmp_input_get_object(qiv, name, true);
> > +    QObject *qobj = qmp_input_get_object(qiv, name, true, errp);
> >  
> > +    if (!qobj) {
> > +        return;
> > +    }
> >      if (qobject_type(qobj) != QTYPE_QNULL) {
> >          error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name :
> >          "null",
> >                     "null");
> 
> Same bug, I think, but I don't have a reproducer handy.
> 
> > @@ -358,7 +397,7 @@ static void qmp_input_type_null(Visitor *v, const char
> > *name, Error **errp)
> >  static void qmp_input_optional(Visitor *v, const char *name, bool
> >  *present)
> >  {
> >      QmpInputVisitor *qiv = to_qiv(v);
> > -    QObject *qobj = qmp_input_get_object(qiv, name, false);
> > +    QObject *qobj = qmp_input_get_object(qiv, name, false, NULL);
> >  
> >      if (!qobj) {
> >          *present = false;
>