Re: [PATCH 2/4] chardev: fix qemu_chr_open_fd() with fd_in==fd_out

From: "Daniel P. Berrangé" <berrange@redhat.com>
To: marcandre.lureau@redhat.com
Cc: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Subject: Re: [PATCH 2/4] chardev: fix qemu_chr_open_fd() with fd_in==fd_out
Date: Tue, 3 Aug 2021 09:44:08 +0100	[thread overview]
Message-ID: <YQkB2OVWERulr/UQ@redhat.com> (raw)
In-Reply-To: <20210723102825.1790112-3-marcandre.lureau@redhat.com>

On Fri, Jul 23, 2021 at 02:28:23PM +0400, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> The "serial" chardev calls qemu_chr_open_fd() with the same fd. This
> may lead to double-close as each QIOChannel owns the fd.
> 
> Instead, share the reference to the same QIOChannel.
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>  chardev/char-fd.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/chardev/char-fd.c b/chardev/char-fd.c
> index ee85a52c06..32166182bf 100644
> --- a/chardev/char-fd.c
> +++ b/chardev/char-fd.c
> @@ -139,13 +139,24 @@ void qemu_chr_open_fd(Chardev *chr,
>          qio_channel_set_name(QIO_CHANNEL(s->ioc_in), name);
>          g_free(name);
>      }
> -    if (fd_out >= 0) {
> +
> +    if (fd_out < 0) {
> +        return;
> +    }
> +
> +    if (fd_out == fd_in) {
> +        s->ioc_out = QIO_CHANNEL(object_ref(s->ioc_in));
> +        name = g_strdup_printf("chardev-file-%s", chr->label);
> +        qio_channel_set_name(QIO_CHANNEL(s->ioc_in), name);
> +        g_free(name);

This is overwriting the name set a few lines earlier. I think the
code ought to be refactor to eliminate this duplication.

ie

  if (fd_out == fd_in) {
    s->ioc_out = s->ioc_in = QIO_CHANNEL(qio_channel_file_new_fd(fd_in));
    ....
  } else {
    s->ioc_in = QIO_CHANNEL(qio_channel_file_new_fd(fd_in));
    ...
    s->ioc_out = QIO_CHANNEL(qio_channel_file_new_fd(fd_out));
    ...
  }

> +    } else {
>          s->ioc_out = QIO_CHANNEL(qio_channel_file_new_fd(fd_out));
>          name = g_strdup_printf("chardev-file-out-%s", chr->label);
>          qio_channel_set_name(QIO_CHANNEL(s->ioc_out), name);
>          g_free(name);
> -        qemu_set_nonblock(fd_out);
>      }
> +
> +    qemu_set_nonblock(fd_out);
>  }
>  
>  static void char_fd_class_init(ObjectClass *oc, void *data)
> -- 
> 2.32.0.264.g75ae10bc75
> 

Regards,
Daniel
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