[Spice-devel] [spice-gtk v1 2/2] channel-usbredir: Fix crash on channel-up

[Christophe Fergeau]

On Tue, Apr 10, 2018 at 02:17:45PM +0200, Victor Toso wrote:
> Hi,
> 
> On Tue, Apr 10, 2018 at 01:37:05PM +0200, Victor Toso wrote:
> > Hi,
> > 
> > On Tue, Apr 10, 2018 at 12:41:16PM +0200, Christophe Fergeau wrote:
> > > On Fri, Apr 06, 2018 at 09:59:44AM +0200, Victor Toso wrote:
> > > > From: Victor Toso <me at victortoso.com>
> > > > 
> > > > By adding a guard to not handle channel-up on SpiceUsbredirChannel in
> > > > case struct usbredirhost wasn't initialized yet. Same guard is in
> > > > place for the generic usbredir_handle_msg() function to avoid handling
> > > > Server's message while Client's initialization is not done.
> > > > 
> > > > As mentioned in commit 291f3e4419e6, this isn't a problem for
> > > > graphical clients as some initialization is done to present the
> > > > shareable usb devices to user.
> > > > 
> > > > Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1399838
> > > > ---
> > > >  src/channel-usbredir.c | 1 +
> > > >  1 file changed, 1 insertion(+)
> > > > 
> > > > diff --git a/src/channel-usbredir.c b/src/channel-usbredir.c
> > > > index f509e49..6df3b61 100644
> > > > --- a/src/channel-usbredir.c
> > > > +++ b/src/channel-usbredir.c
> > > > @@ -819,6 +819,7 @@ static void spice_usbredir_channel_up(SpiceChannel *c)
> > > >      SpiceUsbredirChannel *channel = SPICE_USBREDIR_CHANNEL(c);
> > > >      SpiceUsbredirChannelPrivate *priv = channel->priv;
> > > >  
> > > > +    g_return_if_fail(priv->host != NULL);
> > > 
> > > If this triggers, does this indicates an issue with spice-gtk
> > > code that we need to fix? Or do we just want to ignore
> > > spice_usbredir_channel_up() if host in not set yet?
> > 
> > IMHO, for UI clients like remote-viewer or gnome-boxes, this
> > critical is a problem that needs to be fixed. Same should go on
> > migration. But I haven't seen this been triggered and that's
> > because spice-gtk already calls spice_usb_device_manager_get() in
> > other places.
> > 
> > For non UI tools like spicy-stats, this can be fixed by calling
> > spice_usb_device_manager_get() or disabling usbredir.
> > 
> > Considering that it is possible to have a connection between
> > spice-server and spice-gtk where priv->host is not set, this
> > guard makes sense.
> 
> Sorry, I sent it before I've finished.
> 
> So, I think the guard makes sense to either solve this in the
> client or find where in spice-gtk this might be an issue, if it
> appears to be (not the case so far, IMHO).

I was not questioning the existence of the test, but wondering if this
should be
    g_return_if_fail(priv->host != NULL);
or
    if (priv->host == NULL) return;

Christophe
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