Re: [Qemu-devel] [PATCH v10 10/24] migration: In case of error just end the migration

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Mar 07, 2018 at 11:59:56AM +0100, Juan Quintela wrote:
> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---
>  migration/socket.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

> diff --git a/migration/socket.c b/migration/socket.c
> index 08606c665d..b12b0a462e 100644
> --- a/migration/socket.c
> +++ b/migration/socket.c
> @@ -139,9 +139,8 @@ static gboolean socket_accept_incoming_migration(QIOChannel *ioc,
>      sioc = qio_channel_socket_accept(QIO_CHANNEL_SOCKET(ioc),
>                                       &err);
>      if (!sioc) {
> -        error_report("could not accept migration connection (%s)",
> -                     error_get_pretty(err));
> -        goto out;
> +        migrate_set_error(migrate_get_current(), err);
> +        return G_SOURCE_REMOVE;

It will only return NULL if a client connected & then went away. This should
not happen with a "normal" mgmt app usage. On the flip side this allows a
malicious network attacker to inflict a denial of service on the migration
by simply connecting to target QEMU & immediately exiting.

Our "authentication" for migration relies on being able to validate the TLS
certs during TLS handshake. So in general we ought to allow repeated incoming
connections until we get a successful handshake. 

So in fact, I think a better fix here is to simply remove the original
'error_report' line, and ensure we return G_SOURCE_CONTINUE to wait for
another incoming connection from the real mgmt app.

>      }
>  
>      trace_migration_socket_incoming_accepted();
> @@ -150,7 +149,6 @@ static gboolean socket_accept_incoming_migration(QIOChannel *ioc,
>      migration_channel_process_incoming(QIO_CHANNEL(sioc));
>      object_unref(OBJECT(sioc));
>  
> -out:
>      if (migration_has_all_channels()) {
>          /* Close listening socket as its no longer needed */
>          qio_channel_close(ioc, NULL);
> -- 
> 2.14.3
> 
> 

Regards,
Daniel
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