Re: [PATCH v7 4/5] hw/mem/cxl-type3: Add CXL CDAT Data Object Exchange

[Jonathan Cameron via <qemu-devel@nongnu.org>]

On Wed, 12 Oct 2022 12:01:54 -0400
Gregory Price <gregory.price@memverge.com> wrote:

> This code contains heap corruption on free, and I think should be
> refactored to pre-allocate all the entries we're interested in putting
> into the table.  This would flatten the code and simplify the error
> handling steps.
> 
> Also, should we consider making a union with all the possible entries to
> make entry allocation easier?  It may eat a few extra bytes of memory,
> but it would simplify the allocation/cleanup code here further.
> 
> Given that every allocation has to be checked, i'm also not convinced
> the use of g_autofree is worth the potential footguns associated with
> it.
> 
> > diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> > index 568c9d62f5..3fa5d70662 100644
> > --- a/hw/mem/cxl_type3.c
> > +++ b/hw/mem/cxl_type3.c
> > @@ -12,9 +12,218 @@
> > +static int ct3_build_cdat_table(CDATSubHeader ***cdat_table,
> > +                                void *priv)
> > +{  
> (snip)
> > +        /* For now, no memory side cache, plausiblish numbers */
> > +        dslbis_nonvolatile = g_malloc(sizeof(*dslbis_nonvolatile) * dslbis_nonvolatile_num);
> > +        if (!dslbis_nonvolatile)
> > +            return -ENOMEM;  
> 
> this allocation creates a table of entries, which is later freed
> incorrectly
> 
> > +
> > +    *cdat_table = g_malloc0(len * sizeof(*cdat_table));  
> 
> this allocation needs to be checked
I just realized that sizeof should be sizeof(**cdat_table)

I've moved to a local autofree pointer after factoring out the
guts of the code so this gets simpler anyway (and was more obviously wrong!)

Jonathan