[Spice-devel] [PATCH v2] Handle flow control without crashing for agent

[Uri Lublin]

On 05/31/2016 03:06 PM, Frediano Ziglio wrote:
> RedCharDevice used for the agent has flow control enabled.
> This make possible for red_char_device_write_buffer_get to return NULL.
> Handle such situation without crashing avoiding NULL dereference.
>
> This fixes https://bugs.freedesktop.org/show_bug.cgi?id=95416.

Hi Frediano

Ack.

I'd like to mention that there may be other cases where
red_char_device_write_buffer_get returns NULL, and
that the case you mentioned is the one happens on
fdo bug 95416 mentioned above.

Regards,
     Uri

>
> Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
> ---
>  server/reds.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> Changes from v1:
> - put inline comment to explain the reason of the check.
>
> Victor (bug reporter) tested this patch successfully.
>
> diff --git a/server/reds.c b/server/reds.c
> index e4d806c..f8cfdfb 100644
> --- a/server/reds.c
> +++ b/server/reds.c
> @@ -1120,6 +1120,11 @@ uint8_t *reds_get_agent_data_buffer(RedsState *reds, MainChannelClient *mcc, siz
>      dev->priv->recv_from_client_buf = red_char_device_write_buffer_get(RED_CHAR_DEVICE(dev),
>                                                                         client,
>                                                                         size + sizeof(VDIChunkHeader));



> +    /* check if buffer was allocated, as flow control is enabled for
> +     * this device this is a normal condition */
> +    if (!dev->priv->recv_from_client_buf) {
> +        return NULL;
> +    }
>      dev->priv->recv_from_client_buf_pushed = FALSE;
>      return dev->priv->recv_from_client_buf->buf + sizeof(VDIChunkHeader);
>  }
>