Hi On Thu, Feb 28, 2019 at 8:12 PM Jakub Janků <jjanku@xxxxxxxxxx> wrote: > > If two grab messages in opposite directions "meet" on their way > to their destinations, we end up in a state when both spice-gtk > and spice-vdagent think that the other component can provide > clipboard data. As a consequence of this, neither of them can. > > This is a bug in the spice-protocol. To mitigate the issue, > accept grab only from the side that currently has keyboard focus, > this means: > (1) spice-gtk has focus ==> > * accept grabs from vdagent, > * ignore grabs from other apps running in the host > (2) spice-gtk doesn't have focus ==> > * accept grabs from other apps running in the host > * ignore grabs from vdagent > > The check in clipboard_owner_change() is X11-specific, > because on Wayland, spice-gtk is first notified about the > owner-change once it gains focus. > > The check in clipboard_grab() can be generic. > Note that on Wayland, calling gtk_clipboard_set_with_owner() > while not having focus doesn't have any effect anyway, > only focused clients can set clipboard. > > With this patch, the race can still occur around the time > when focus changes (rare, but possible), on X11 as well as Wayland. > > Related: https://gitlab.freedesktop.org/spice/spice-gtk/issues/82 > Related: https://bugzilla.redhat.com/show_bug.cgi?id=1594876 > > Signed-off-by: Jakub Janků <jjanku@xxxxxxxxxx> > --- > > Victor, half of this patch is basically yours, > so feel free to add signed-off or something, > in the case this gets upstream :) > > --- > src/spice-gtk-session.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/src/spice-gtk-session.c b/src/spice-gtk-session.c > index b48f92a..7b7370c 100644 > --- a/src/spice-gtk-session.c > +++ b/src/spice-gtk-session.c > @@ -680,6 +680,13 @@ static void clipboard_owner_change(GtkClipboard *clipboard, > s->clip_hasdata[selection] = FALSE; > return; > } > + > + if (GDK_IS_X11_DISPLAY(gdk_display_get_default()) && > + spice_gtk_session_get_keyboard_has_focus(self)) { > + SPICE_DEBUG("%s: spice-gtk has keyboard focus, " > + "ignoring grab from other app", __FUNCTION__); > + return; > + } > #endif This will break clipboard managers interactions, which may take the clipboard content, save it and/or modify it. > > s->clip_hasdata[selection] = TRUE; > @@ -823,6 +830,12 @@ static gboolean clipboard_grab(SpiceMainChannel *main, guint selection, > cb = get_clipboard_from_selection(s, selection); > g_return_val_if_fail(cb != NULL, FALSE); > > + if (!spice_gtk_session_get_keyboard_has_focus(self)) { > + SPICE_DEBUG("%s: spice-gtk doesn't have keyboard focus, " > + "ignoring grab from guest agent", __FUNCTION__); > + return FALSE; > + } Beside automation, the cursor alone may easily create a new clipboard content which won't be available to the client side (the auto-grab may fail to follow cursor etc). It's a bit unclear why it's not X11 specific but for client side change it is, this could deserve a code comment. All in all, this feels weak and breaks some legitimate cases. I am not very strongly against this, as I understand it may help with some races we discussed, but it feels like the problem is elsewhere and we need a better solution to prevent the race from happening. I haven't read the bug reports: this kind of workaround needs a description of a broken use case (not a theoretical description of a race that "never" happen in practice). > + > for (n = 0; n < ntypes; ++n) { > found = FALSE; > for (m = 0; m < SPICE_N_ELEMENTS(atom2agent); m++) { > -- > 2.20.1 > > _______________________________________________ > Spice-devel mailing list > Spice-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/spice-devel -- Marc-André Lureau _______________________________________________ Spice-devel mailing list Spice-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/spice-devel