Created attachment 42484 [details]
Backtrace of crash.

When full-screen application is running and I am changing volume from keyboard, kwin(KDE's window manager) is crashing. Usually, when one changes a volume in KDE, a progress-window appears. Full screen application in my case - Angry Birds game(Wine).

Bug appears only when I am using a OpenGL compositing, with XRender compositing all is OK.

Bug is quite reproductable. I tested it with mesa from git and with mesa 7.10. I have a Intel Corporation Mobile GM965 Graphics Controller.

I think there is a problem with prepare_wm_surfaces(..) in mesa/drivers/dri/i965/brw_wm_surface_state.c :
   if (ctx->DrawBuffer->_NumColorDrawBuffers >= 1) {
      for (i = 0; i < ctx->DrawBuffer->_NumColorDrawBuffers; i++) {

        struct gl_renderbuffer *rb = ctx->DrawBuffer->_ColorDrawBuffers[i];
        struct intel_renderbuffer *irb = intel_renderbuffer(rb);
        struct intel_region *region = irb ? irb->region : NULL;
        brw_add_validated_bo(brw, region->buffer);
        ........

When irb is NULL, region is NULL too, and region->buffer causes a segfault.