Re: [PATCH v3 16/19] migration: Export tls-[creds|hostname|authz] params to cmdline too

[Peter Xu]

On Wed, Mar 30, 2022 at 05:39:05PM -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.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  migration/migration.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index 899084f993..d99a0ecb7b 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),
> -- 

This simple patch will cause a double-free issue on tls-creds, etc. because
the properties are released before migration object, and since we also
explicitly free tls_* fields in migration_instance_finalize() then it hits
double free.  The details is in object_finalize() where the order is:

    object_property_del_all(obj);
    object_deinit(obj, ti);

It was overlooked when I was testing the preempt+tls functionality and
it'll trigger when we need a graceful quit of qemu.

Meanwhile there's another patch ordering issue I didn't notice when I post
this version: patch "migration: Add helpers to detect TLS capability" needs
to be before "migration: Enable TLS for preempt channel".  No code change
for this, it just needs some re-ordering to guarantee per-commit builds to
be successful.

I'll respin another version..

-- 
Peter Xu