Bug#1131016: gtk+3.0: refresh_rate calculation overflows on 32-bit targets

[Alberto Garcia]

Source: gtk+3.0
Version: 3.24.49-3
Severity: normal
Tags: upstream patch

Hi,

gdk_monitor_get_refresh_rate() overflows on 32-bit systems, returning
a bogus value. This has been confirmed to crash webkitgtk-based apps
(#1085710).

The problem is in this line from gdk/x11/gdkscreen-x11.c (there are
actually two of them in the file):

   refresh_rate = (1000 * xmode->dotClock) / (xmode->hTotal * xmode->vTotal);

xmode->dotClock is an unsigned long (32 bits in i386) so a pixel clock
of e.g. 106500000 will result in an overflow.

I confirmed that using 1000ULL instead of 1000 solves the crash (patch
attached), but in case you prefer to wait for the upstream fix, here's
the issue:

   https://gitlab.gnome.org/GNOME/gtk/-/issues/8103

Regards,

Berto

Index: gtk+3.0-3.24.49/gdk/x11/gdkscreen-x11.c
===================================================================
--- gtk+3.0-3.24.49.orig/gdk/x11/gdkscreen-x11.c
+++ gtk+3.0-3.24.49/gdk/x11/gdkscreen-x11.c
@@ -587,7 +587,7 @@ init_randr15 (GdkScreen *screen, gboolea
               if (xmode->id == crtc->mode)
                 {
                   if (xmode->hTotal != 0 && xmode->vTotal != 0)
-                    refresh_rate = (1000 * xmode->dotClock) / (xmode->hTotal * 
xmode->vTotal);
+                    refresh_rate = (1000ULL * xmode->dotClock) / 
(xmode->hTotal * xmode->vTotal);
                   break;
                 }
             }
@@ -837,7 +837,7 @@ init_randr13 (GdkScreen *screen, gboolea
               if (xmode->id == crtc->mode)
                 {
                   if (xmode->hTotal != 0 && xmode->vTotal != 0)
-                    refresh_rate = (1000 * xmode->dotClock) / (xmode->hTotal * 
xmode->vTotal);
+                    refresh_rate = (1000ULL * xmode->dotClock) / 
(xmode->hTotal * xmode->vTotal);
                   break;
                 }
             }