Re: [PATCH] migration: Don't free the reason after calling migrate_add_blocker

[Bin Guo <guobin@linux.alibaba.com>]

Markus Armbruster <armbru@redhat.com> writes:

> > Signed-off-by: Bin Guo <guobin@linux.alibaba.com>
> > ---
> >  hw/intc/arm_gicv3_kvm.c | 1 -
> >  target/i386/sev.c       | 1 -
> >  2 files changed, 2 deletions(-)
> >
> > diff --git a/hw/intc/arm_gicv3_kvm.c b/hw/intc/arm_gicv3_kvm.c
> > index 66b0dddfd4..6f311e37ef 100644
> > --- a/hw/intc/arm_gicv3_kvm.c
> > +++ b/hw/intc/arm_gicv3_kvm.c
> > @@ -841,7 +841,6 @@ static void kvm_arm_gicv3_realize(DeviceState *dev, Error **errp)
> >          error_setg(&kvm_nv_migration_blocker,
> >                     "Live migration disabled because KVM nested virt is enabled");
> >          if (migrate_add_blocker(&kvm_nv_migration_blocker, errp)) {
> > -            error_free(kvm_nv_migration_blocker);
> >              return;
> >          }
> >  
> > diff --git a/target/i386/sev.c b/target/i386/sev.c
> > index 1057b8ab2c..fd2dada013 100644
> > --- a/target/i386/sev.c
> > +++ b/target/i386/sev.c
> > @@ -1661,7 +1661,6 @@ sev_snp_launch_finish(SevCommonState *sev_common)
> >      ret = migrate_add_blocker(&sev_mig_blocker, &local_err);
> >      if (local_err) {
> >          error_report_err(local_err);
> > -        error_free(sev_mig_blocker);
> >          exit(1);
> >      }
> >  }
> 
> Does this fix use-after-free bugs?

No, just delete the unnecessary code and follow the best practice.
Function migrate_add_blocker will free the reason and set it to NULL
if failure is returned.