Re: [Qemu-devel] [PATCH 2/8] block: fix unbounded stack for dump_qdict

[Peter Xu]

On Tue, Mar 08, 2016 at 01:17:03PM +0100, Paolo Bonzini wrote:
> 
> 
> On 08/03/2016 09:12, Markus Armbruster wrote:
> > I'm afraid this isn't a good idea.  It relies on the non-local argument
> > that nobody will ever put a key longer than 255 into a qdict that gets
> > dumped.  That may even be the case, but you need to *prove* it, not just
> > assert it.  The weakest acceptable proof might be assertions in every
> > place that put keys into a dict that might get dumped.  I suspect that's
> > practical and maintainable only if there's a single place that does it.
> > 
> > If this was a good idea, I'd recommend to avoid the awkward macro:
> > 
> >            char key[256];
> >            int i;
> >    
> >            assert(strlen(entry->key) + 1 <= ARRAY_SIZE(key));
> > 
> > There are several other ways to limit the stack usage:
> > 
> > 1. Move the array from stack to heap.  Fine unless it's on a hot path.
> >    As far as I can tell, this dumping business is for HMP and qemu-io,
> >    i.e. not hot.
> 
> I think this is the best.  You can just g_strdup, modify in place, print
> and free.

g_strdup() will bring one more loop? One to copy the strings, one
for replacing "-" to " ". Though I will first need to replace
g_malloc0() with g_malloc(), which seems more suitable here. :)

Thanks!
Peter