[PATCH] ui/gtk: Handle empty notebook state in menu handlers

[dongwon.kim@intel.com]

From: Dongwon Kim <dongwon.kim@intel.com>

When the GTK notebook has no active page (e.g. before pages are added
or if all pages are detached/removed), gtk_notebook_get_current_page()
returns -1. Previously, this value was passed unchecked to
gd_vc_find_by_page(), which could result in unexpected lookups or NULL
dereferences.

Update gd_vc_find_current() to explicitly return NULL when page < 0.
Additionally, add NULL checks for the current VirtualConsole across all
relevant UI menu callbacks to avoid dereferencing an invalid or NULL
pointer when no console tab is currently focused.

Cc: Daniel P. Berrangé <berrange@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
---
 ui/gtk.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 50 insertions(+), 6 deletions(-)

diff --git a/ui/gtk.c b/ui/gtk.c
index 7078d89d67..0b5139ef31 100644
--- a/ui/gtk.c
+++ b/ui/gtk.c
@@ -184,6 +184,11 @@ static VirtualConsole *gd_vc_find_current(GtkDisplayState *s)
     gint page;
 
     page = gtk_notebook_get_current_page(GTK_NOTEBOOK(s->notebook));
+
+    if (page < 0) {
+        return NULL;
+    }
+
     return gd_vc_find_by_page(s, page);
 }
 
@@ -1462,7 +1467,10 @@ static void gd_menu_show_tabs(GtkMenuItem *item, void *opaque)
     } else {
         gtk_notebook_set_show_tabs(GTK_NOTEBOOK(s->notebook), FALSE);
     }
-    gd_update_windowsize(vc);
+
+    if (vc) {
+        gd_update_windowsize(vc);
+    }
 }
 
 static int gd_vc_notebook_pos(GtkDisplayState *s, VirtualConsole *target)
@@ -1535,6 +1543,10 @@ static void gd_menu_untabify(GtkMenuItem *item, void *opaque)
     GtkDisplayState *s = opaque;
     VirtualConsole *vc = gd_vc_find_current(s);
 
+    if (!vc) {
+        return;
+    }
+
     if (vc->type == GD_VC_GFX &&
         qemu_console_is_graphic(vc->gfx.dcl.con)) {
         gtk_check_menu_item_set_active(GTK_CHECK_MENU_ITEM(s->grab_item),
@@ -1588,7 +1600,10 @@ static void gd_menu_show_menubar(GtkMenuItem *item, void *opaque)
     } else {
         gtk_widget_hide(s->menu_bar);
     }
-    gd_update_windowsize(vc);
+
+    if (vc) {
+        gd_update_windowsize(vc);
+    }
 }
 
 static void gd_accel_show_menubar(void *opaque)
@@ -1605,7 +1620,7 @@ static void gd_menu_full_screen(GtkMenuItem *item, void *opaque)
     if (!s->full_screen) {
         gtk_notebook_set_show_tabs(GTK_NOTEBOOK(s->notebook), FALSE);
         gtk_widget_hide(s->menu_bar);
-        if (vc->type == GD_VC_GFX) {
+        if (vc && vc->type == GD_VC_GFX) {
             gtk_widget_set_size_request(vc->gfx.drawing_area, -1, -1);
         }
         gtk_window_fullscreen(GTK_WINDOW(s->window));
@@ -1618,14 +1633,16 @@ static void gd_menu_full_screen(GtkMenuItem *item, void *opaque)
             gtk_widget_show(s->menu_bar);
         }
         s->full_screen = FALSE;
-        if (vc->type == GD_VC_GFX) {
+        if (vc && vc->type == GD_VC_GFX) {
             vc->gfx.scale_x = vc->gfx.preferred_scale;
             vc->gfx.scale_y = vc->gfx.preferred_scale;
             gd_update_windowsize(vc);
         }
     }
 
-    gd_update_cursor(vc);
+    if (vc) {
+        gd_update_cursor(vc);
+    }
 }
 
 static void gd_accel_full_screen(void *opaque)
@@ -1639,6 +1656,10 @@ static void gd_menu_zoom_in(GtkMenuItem *item, void *opaque)
     GtkDisplayState *s = opaque;
     VirtualConsole *vc = gd_vc_find_current(s);
 
+    if (!vc) {
+        return;
+    }
+
     gtk_check_menu_item_set_active(GTK_CHECK_MENU_ITEM(s->zoom_fit_item),
                                    FALSE);
 
@@ -1659,6 +1680,10 @@ static void gd_menu_zoom_out(GtkMenuItem *item, void *opaque)
     GtkDisplayState *s = opaque;
     VirtualConsole *vc = gd_vc_find_current(s);
 
+    if (!vc) {
+        return;
+    }
+
     gtk_check_menu_item_set_active(GTK_CHECK_MENU_ITEM(s->zoom_fit_item),
                                    FALSE);
 
@@ -1676,6 +1701,10 @@ static void gd_menu_zoom_fixed(GtkMenuItem *item, void *opaque)
     GtkDisplayState *s = opaque;
     VirtualConsole *vc = gd_vc_find_current(s);
 
+    if (!vc) {
+        return;
+    }
+
     vc->gfx.scale_x = vc->gfx.preferred_scale;
     vc->gfx.scale_y = vc->gfx.preferred_scale;
 
@@ -1687,6 +1716,10 @@ static void gd_menu_zoom_fit(GtkMenuItem *item, void *opaque)
     GtkDisplayState *s = opaque;
     VirtualConsole *vc = gd_vc_find_current(s);
 
+    if (!vc) {
+        return;
+    }
+
     if (gtk_check_menu_item_get_active(GTK_CHECK_MENU_ITEM(s->zoom_fit_item))) {
         s->free_scale = TRUE;
     } else {
@@ -1800,6 +1833,11 @@ static void gd_menu_grab_input(GtkMenuItem *item, void *opaque)
     VirtualConsole *vc = gd_vc_find_current(s);
 
     if (gd_is_grab_active(s)) {
+        if (!vc) {
+            gtk_check_menu_item_set_active(GTK_CHECK_MENU_ITEM(s->grab_item),
+                                           FALSE);
+            return;
+        }
         gd_grab_keyboard(vc, "user-request-main-window");
         gd_grab_pointer(vc, "user-request-main-window");
     } else {
@@ -1807,7 +1845,9 @@ static void gd_menu_grab_input(GtkMenuItem *item, void *opaque)
         gd_ungrab_pointer(s);
     }
 
-    gd_update_cursor(vc);
+    if (vc) {
+        gd_update_cursor(vc);
+    }
 }
 
 static void gd_change_page(GtkNotebook *nb, gpointer arg1, guint arg2,
@@ -1983,6 +2023,10 @@ static void gd_menu_copy(GtkMenuItem *item, void *opaque)
     GtkDisplayState *s = opaque;
     VirtualConsole *vc = gd_vc_find_current(s);
 
+    if (!vc) {
+        return;
+    }
+
 #if VTE_CHECK_VERSION(0, 50, 0)
     vte_terminal_copy_clipboard_format(VTE_TERMINAL(vc->vte.terminal),
                                        VTE_FORMAT_TEXT);
-- 
2.43.0