Re: [PATCH v4 15/19] migration: Export tls-[creds|hostname|authz] params to cmdline too

[Daniel P . Berrangé]

On Thu, Mar 31, 2022 at 11:08:53AM -0400, Peter Xu wrote:
> It's useful for specifying tls credentials all in the cmdline (along with
> the -object tls-creds-*), especially for debugging purpose.
> 
> The trick here is we must remember to not free these fields again in the
> finalize() function of migration object, otherwise it'll cause double-free.
> 
> The thing is when destroying an object, we'll first destroy the properties
> that bound to the object, then the object itself.  To be explicit, when
> destroy the object in object_finalize() we have such sequence of
> operations:
> 
>     object_property_del_all(obj);
>     object_deinit(obj, ti);
> 
> So after this change the two fields are properly released already even
> before reaching the finalize() function but in object_property_del_all(),
> hence we don't need to free them anymore in finalize() or it's double-free.


I believe this is also fixing a small memory leak

> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  migration/migration.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index 899084f993..1dc80be1f4 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -4349,6 +4349,9 @@ static Property migration_properties[] = {
>                        DEFAULT_MIGRATE_ANNOUNCE_STEP),
>      DEFINE_PROP_BOOL("x-postcopy-preempt-break-huge", MigrationState,
>                        postcopy_preempt_break_huge, true),
> +    DEFINE_PROP_STRING("tls-creds", MigrationState, parameters.tls_creds),
> +    DEFINE_PROP_STRING("tls-hostname", MigrationState, 
> parameters.tls_hostname),
> +    DEFINE_PROP_STRING("tls-authz", MigrationState, parameters.tls_authz),
>  
>      /* Migration capabilities */
>      DEFINE_PROP_MIG_CAP("x-xbzrle", MIGRATION_CAPABILITY_XBZRLE),
> @@ -4382,12 +4385,9 @@ static void migration_class_init(ObjectClass *klass, 
> void *data)
>  static void migration_instance_finalize(Object *obj)
>  {
>      MigrationState *ms = MIGRATION_OBJ(obj);
> -    MigrationParameters *params = &ms->parameters;
>  
>      qemu_mutex_destroy(&ms->error_mutex);
>      qemu_mutex_destroy(&ms->qemu_file_lock);
> -    g_free(params->tls_hostname);
> -    g_free(params->tls_creds);

tls_authz wasn't previously freed here, and now it will be

>      qemu_sem_destroy(&ms->wait_unplug_sem);
>      qemu_sem_destroy(&ms->rate_limit_sem);
>      qemu_sem_destroy(&ms->pause_sem);

With regards,
Daniel
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