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

[Frediano Ziglio]

> 
> Hi,
> 
> On Tue, May 31, 2016 at 11:20:04AM +0100, 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.
> > 
> > Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
> > ---
> >  server/reds.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/server/reds.c b/server/reds.c
> > index e4d806c..72dee84 100644
> > --- a/server/reds.c
> > +++ b/server/reds.c
> > @@ -1120,6 +1120,9 @@ 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));
> > +    if (!dev->priv->recv_from_client_buf) {
> > +        return NULL;
> > +    }
> 
> Is this expected? If not, maybe a g_return_val_if_fail would fit better.
> 

Thought was clear from the comment.
Yes, in case of flow control it's the way char device tell the
user of the class to wait.
There is already a warning in char device.

> >      dev->priv->recv_from_client_buf_pushed = FALSE;
> >      return dev->priv->recv_from_client_buf->buf + sizeof(VDIChunkHeader);
> >  }

Frediano