Re: [Qemu-devel] [PATCH] char: don't skip client cleanup if 'connected' flag is unset

[Marc-André Lureau]

Hi

On Thu, Oct 5, 2017 at 5:28 PM, Daniel P. Berrange <address@hidden> wrote:
> The tcp_chr_free_connection & tcp_chr_disconnect methods both
> skip all of their cleanup work unless the 's->connected' flag
> is set.  This flag is set when the incoming client connection
> is ready to use. Crucially this is *after* the TLS handshake
> has been completed. So if the TLS handshake fails and we try
> to cleanup the failed client, all the cleanup is skipped as
> 's->connected' is still false.
>
> The only important thing that should be skipped in this case
> is sending of the CHR_EVENT_CLOSED, because we never got as
> far as sending the corresponding CHR_EVENT_OPENED. Every other
> bit of cleanup can be robust against being called even when
> s->connected is false.
>
> Signed-off-by: Daniel P. Berrange <address@hidden>
> ---
>  chardev/char-socket.c | 31 +++++++++++++++++--------------
>  1 file changed, 17 insertions(+), 14 deletions(-)
>
> diff --git a/chardev/char-socket.c b/chardev/char-socket.c
> index e65148fe97..a34d4d72c2 100644
> --- a/chardev/char-socket.c
> +++ b/chardev/char-socket.c
> @@ -332,10 +332,6 @@ static void tcp_chr_free_connection(Chardev *chr)
>      SocketChardev *s = SOCKET_CHARDEV(chr);
>      int i;
>
> -    if (!s->connected) {
> -        return;
> -    }
> -
>      if (s->read_msgfds_num) {
>          for (i = 0; i < s->read_msgfds_num; i++) {
>              close(s->read_msgfds[i]);
> @@ -347,10 +343,14 @@ static void tcp_chr_free_connection(Chardev *chr)
>
>      tcp_set_msgfds(chr, NULL, 0);
>      remove_fd_in_watch(chr);
> -    object_unref(OBJECT(s->sioc));
> -    s->sioc = NULL;
> -    object_unref(OBJECT(s->ioc));
> -    s->ioc = NULL;
> +    if (s->sioc) {
> +        object_unref(OBJECT(s->sioc));
> +        s->sioc = NULL;
> +    }
> +    if (s->ioc) {
> +        object_unref(OBJECT(s->ioc));
> +        s->ioc = NULL;
> +    }

object_unref() and OBJECT() are null-safe.

>      g_free(chr->filename);
>      chr->filename = NULL;
>      s->connected = 0;
> @@ -394,22 +394,25 @@ static void update_disconnected_filename(SocketChardev 
> *s)
>                                           s->is_listen, s->is_telnet);
>  }
>
> +/* NB may be called even if tcp_chr_connect has not been
> + * reached, due to TLS or telnet initialization failure,
> + * so can *not* assume s->connected == true
> + */
>  static void tcp_chr_disconnect(Chardev *chr)
>  {
>      SocketChardev *s = SOCKET_CHARDEV(chr);
> -
> -    if (!s->connected) {
> -        return;
> -    }
> +    bool emitClose = s->connected;

ewh, which code style do you pick today? :)

>
>      tcp_chr_free_connection(chr);
>
> -    if (s->listen_ioc) {
> +    if (s->listen_ioc && s->listen_tag == 0) {
>          s->listen_tag = qio_channel_add_watch(
>              QIO_CHANNEL(s->listen_ioc), G_IO_IN, tcp_chr_accept, chr, NULL);
>      }
>      update_disconnected_filename(s);
> -    qemu_chr_be_event(chr, CHR_EVENT_CLOSED);
> +    if (emitClose) {
> +        qemu_chr_be_event(chr, CHR_EVENT_CLOSED);
> +    }
>      if (s->reconnect_time) {
>          qemu_chr_socket_restart_timer(chr);
>      }
> --
> 2.13.5
>
>

other than that, looks good to me

-- 
Marc-André Lureau