Re: [Qemu-devel] [PATCH] spapr: fix write-past-end-of-array error in cpu core device init code

[Greg Kurz]

On Tue, 28 Jun 2016 12:55:07 +1000
David Gibson <address@hidden> wrote:

> On Mon, Jun 27, 2016 at 06:28:15PM +0200, Greg Kurz wrote:
> > This fixes a potential QEMU crash introduced by commit 3b542549661.
> > 
> > Signed-off-by: Greg Kurz <address@hidden>
> > ---
> >  hw/ppc/spapr_cpu_core.c |    3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)  
> 
> Ugh.  The existing code is wrong in the case where the failure happens
> after the loop.
> 
> But this version is wrong in the case it happens during the loop - it
> will fail to clean up the last object created.
> 

Hmm... unless I'm missing something, if object_property_add_child() fails to
add object i, we don't want to unparent it, and we should start rollback
at index i-1.

Another weirdness is that I see no rollback for the object_child_foreach()
loop: in case of failure, we will unparent realized objects... is it okay ?

> > diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> > index 3a5da09b9902..8b802a6fcf0b 100644
> > --- a/hw/ppc/spapr_cpu_core.c
> > +++ b/hw/ppc/spapr_cpu_core.c
> > @@ -309,10 +309,9 @@ static void spapr_cpu_core_realize(DeviceState *dev, 
> > Error **errp)
> >      }
> >  
> >  err:
> > -    while (i >= 0) {
> > +    while (--i >= 0) {
> >          obj = sc->threads + i * size;
> >          object_unparent(obj);
> > -        i--;
> >      }
> >      g_free(sc->threads);
> >      error_propagate(errp, local_err);
> >   
>

pgpXOYBKaYX6x.pgp
Description: OpenPGP digital signature