Re: [PATCH 13/13] Turn virNetClient* into virObject instances

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

On Tue, Jul 17, 2012 at 02:36:18PM -0600, Eric Blake wrote:
> On 07/11/2012 07:35 AM, Daniel P. Berrange wrote:
> > From: "Daniel P. Berrange" <berrange@xxxxxxxxxx>
> > 
> > Make all the virNetClient* objects use virObject APIs for
> > reference counting
> > 
> > Signed-off-by: Daniel P. Berrange <berrange@xxxxxxxxxx>
> > ---
> 
> > @@ -286,19 +294,22 @@ static virNetClientPtr virNetClientNew(virNetSocketPtr sock,
> 
> >  
> > -    if (virMutexInit(&client->lock) < 0)
> > +    if (virMutexInit(&client->lock) < 0) {
> > +        VIR_FREE(client);
> >          goto error;
> 
> Hmm - this discards the fact that client has a ref-count of 1, and thus
> fails to poison that memory (one of the benefits of always going through
> unref is that that poisoning helps detect use-after-free bugs).
> Thankfully, though, there is no other allocated memory owned by 'client'
> at this point in time, so skipping the dispose method is not technically
> a leak; furthermore, since the dispose method tries to call
> virMutexDestroy but we know the mutex failed to initialize, I think it's
> the best we can do.  You made me think about this, but in the end I
> agree it is right, even though it looks fishy.

FYI, this will be temporary nastiness.  I intend to actually add a
virMutex to the virObjectPtr base object in a future patch series,
so subclasses won't need to maintain their own mutexes. So we'll
easily be able todo the right thing wrt to poisoning then.


Daniel
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