Re: [Qemu-devel] [PATCH v3 17/19] target-i386: fix apic object leak when CPU is deleted

[Igor Mammedov]

On Wed, 13 Jul 2016 12:04:44 -0300
Eduardo Habkost <address@hidden> wrote:

> On Wed, Jul 06, 2016 at 08:20:53AM +0200, Igor Mammedov wrote:
> > Signed-off-by: Igor Mammedov <address@hidden>
> > ---
> >  target-i386/cpu.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > index 04c0b79..2fa445d 100644
> > --- a/target-i386/cpu.c
> > +++ b/target-i386/cpu.c
> > @@ -2765,6 +2765,7 @@ static void x86_cpu_apic_create(X86CPU *cpu, Error 
> > **errp)
> >  
> >      object_property_add_child(OBJECT(cpu), "lapic",
> >                                OBJECT(cpu->apic_state), &error_abort);
> > +    object_unref(OBJECT(cpu->apic_state));  
> 
> What kind of event can trigger object_unparent() or
> object_del_property() on "lapic"? Can we guarantee that the child
> property will never be deleted by any other code, only by
> x86_cpu_unrealizefn() and object_finalize(cpu)?
code path that triggers unparent of lapic implicitly is
cpu instance removal when it deletes all children.

So unless someone adds explicit lapic removal somewhere in target-i386/cpu.c
I don't see how it could be deleted by other code path.

> Because with this change, deleting the property will leave us
> with with a dangling cpu->apic_state pointer.
since there aren't other place that deletes lapic property we won't get it
dangling pointer, see the next patch comment for call chain

> 
> >  
> >      qdev_prop_set_uint8(cpu->apic_state, "id", cpu->apic_id);
> >      /* TODO: convert to link<> */
> > -- 
> > 2.7.0
> >   
>