Re: [Qemu-devel] [PATCH] qapi: fix memory leak in QmpOutputVisitor

[Pino Toscano]

On Tuesday, 18 October 2016 06:13:30 CEST Eric Blake wrote:
> On 10/18/2016 04:17 AM, Pino Toscano wrote:
> > qmp_output_start_struct() and qmp_output_start_list() create a new
> > QObject (QDict, QList) and push it to the stack of the QmpOutputVisitor,
> > where it is saved as 'value'.  When freeing the iterator in
> > qmp_output_free(), these values are never freed properly.
> 
> Do any of the tests (perhaps run under valgrind) show this leak? If not,
> maybe we should enhance their coverage.

Running a simple `qemu-img info file.qcow2` under valgrind was enough
for me to show the leak.

In this case, another simple fix is needed to fully fix the leak:
http://lists.nongnu.org/archive/html/qemu-devel/2016-10/msg04023.html
(Yes, I just saw your ACK on this, Eric, just leaving it here for
reference.)

> > 
> > The simple solution is to qobject_decref() them.
> > ---
> >  qapi/qmp-output-visitor.c | 1 +
> >  1 file changed, 1 insertion(+)
> 
> Reviewed-by: Eric Blake <address@hidden>
> 
> > 
> > diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c
> > index 9e3b67c..eedf256 100644
> > --- a/qapi/qmp-output-visitor.c
> > +++ b/qapi/qmp-output-visitor.c
> > @@ -220,6 +220,7 @@ static void qmp_output_free(Visitor *v)
> >      while (!QSLIST_EMPTY(&qov->stack)) {
> >          e = QSLIST_FIRST(&qov->stack);
> >          QSLIST_REMOVE_HEAD(&qov->stack, node);
> > +        qobject_decref(e->value);
> >          g_free(e);
> >      }
> >  
> > 
> 
> 


-- 
Pino Toscano

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