Re: [PATCH 1/2] liveupdate: Use refcount_t for FLB reference counts

[David Matlack]

On Thu, Apr 23, 2026 at 11:11 AM Pasha Tatashin
<pasha.tatashin@xxxxxxxxxx> wrote:
> On 04-23 17:40, David Matlack wrote:

> > @@ -126,8 +126,10 @@ static int luo_flb_file_preserve_one(struct liveupdate_flb *flb)
> >                       }
> >                       private->outgoing.data = args.data;
> >                       private->outgoing.obj = args.obj;
> > +                     refcount_set(&private->outgoing.count, 1);
> > +             } else {
> > +                     refcount_inc(&private->outgoing.count);
> >               }
> > -             private->outgoing.count++;
>
> It should be: refcount_inc(&private->outgoing.count); for both
> cases, as it was before.

Calling refcount_inc() when the refcount is 0 triggers the
REFCOUNT_ADD_UAF warning.

> Additionally, please add refcount_set(&private->outgoing.count, 0) to
> luo_flb_get_private, where the rest of the private fields are
> initialized.

Will do.

> In general, I prefer to avoid refcount_set() because it breaks
> continuity and makes debugging hard. It should only be used only during
> initialization, so moving it to where the other fields are initialized
> is the correct approach.