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Re: [Qemu-devel] [PATCH 02/10] qapi: fail hard on stack imbalance
From: |
Michael Roth |
Subject: |
Re: [Qemu-devel] [PATCH 02/10] qapi: fail hard on stack imbalance |
Date: |
Mon, 26 Mar 2012 10:06:02 -0500 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Mon, Mar 26, 2012 at 11:15:46AM -0300, Luiz Capitulino wrote:
> On Thu, 22 Mar 2012 12:51:04 +0100
> Paolo Bonzini <address@hidden> wrote:
>
> > QmpOutputVisitor will segfault if an imbalanced end function is
> > called. So we can abort in QmpInputVisitor too.
> >
> > Signed-off-by: Paolo Bonzini <address@hidden>
> > ---
> > qapi/qmp-input-visitor.c | 5 +----
> > 1 files changed, 1 insertions(+), 4 deletions(-)
> >
> > diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c
> > index e6b6152..b4013cc 100644
> > --- a/qapi/qmp-input-visitor.c
> > +++ b/qapi/qmp-input-visitor.c
> > @@ -77,11 +77,8 @@ static void qmp_input_push(QmpInputVisitor *qiv, const
> > QObject *obj, Error **err
> >
> > static void qmp_input_pop(QmpInputVisitor *qiv, Error **errp)
> > {
> > + assert(qiv->nb_stack > 0);
> > qiv->nb_stack--;
> > - if (qiv->nb_stack < 0) {
> > - error_set(errp, QERR_BUFFER_OVERRUN);
> > - return;
> > - }
> > }
>
> Just to confirm: this can't be triggered by malicious clients, right?
>
> The original series submitted by Michael had this, but I asked him to
> change because I thought clients could trigger it. But by reading the code
> now it seems to me that the end_struct() function is only generated by types
> we know about.
>
Yah, looked into this as well. I can't see anything outside of a
bug triggering this: even if they did manage to get past the parser and
have some wonky qobject fed to us, the generated visitor code should
still always be balanced, and end_list/end_struct are the only way to
induce a pop so nb_stack should never go below 0. There may be other areas
where we need to watch out for this kind of stuff though.
> >
> > static void qmp_input_start_struct(Visitor *v, void **obj, const char
> > *kind,
>
>
- [Qemu-devel] [PATCH 00/10] QAPI minor fixes and strict mode, Paolo Bonzini, 2012/03/22
- [Qemu-devel] [PATCH 02/10] qapi: fail hard on stack imbalance, Paolo Bonzini, 2012/03/22
- [Qemu-devel] [PATCH 01/10] qapi: add a test case for type errors, Paolo Bonzini, 2012/03/22
- [Qemu-devel] [PATCH 04/10] qapi: shortcut visits on errors, Paolo Bonzini, 2012/03/22
- [Qemu-devel] [PATCH 03/10] qapi: fix memory leak on error, Paolo Bonzini, 2012/03/22
- [Qemu-devel] [PATCH 05/10] qapi: allow freeing partially-allocated objects, Paolo Bonzini, 2012/03/22
- [Qemu-devel] [PATCH 06/10] qapi: simplify qmp_input_next_list, Paolo Bonzini, 2012/03/22