[RESEND PATCH weston v3] pixman: Destroy pixman images when underlying buffer is destroyed

[Lubomir Rintel]

On Mon, 2013-12-02 at 15:53 -0800, Kristian Høgsberg wrote:
> On Sat, Nov 30, 2013 at 03:41:00PM +0100, Lubomir Rintel wrote:
> > While the pixman image might be attached, the underlying buffer might be
> > already gone under certain circumstances. This is easily reproduced by
> > attempting to resize gnome-terminal on a fbdev backend.
> > 
> > $ WAYLAND_DEBUG=1 strace -emunmap weston --backend=fbdev-backend.so
> > ...
> > [1524826.942] wl_shm at 7.create_pool(new id wl_shm_pool at 23, fd 40, 1563540)
> > [1524827.315] wl_shm_pool at 23.create_buffer(new id wl_buffer at 24, 0, 759, 515, 3036, 0)
> > ...
> > [1524829.488] wl_surface at 14.attach(wl_buffer at 24, 0, 0)
> > [1524829.766] wl_surface at 14.set_buffer_scale(1)
> > [1524829.904] wl_surface at 14.damage(0, 0, 759, 515)
> > [1524830.248] wl_surface at 14.frame(new id wl_callback at 25)
> > [1524830.450] wl_surface at 14.commit()
> > ...
> > [1524846.706] wl_shm at 7.create_pool(new id wl_shm_pool at 26, fd 40, 1545000)
> > [1524847.215] wl_shm_pool at 26.create_buffer(new id wl_buffer at 27, 0, 750, 515, 3000, 0)
> > [1524847.735] wl_buffer at 24.destroy()
> > [1524847.953]  -> wl_display at 1.delete_id(24)
> > [1524848.144] wl_shm_pool at 23.destroy()
> > munmap(0xb5b2e000, 1563540)             = 0
> > [1524849.021]  -> wl_display at 1.delete_id(23)
> > [1524849.425] wl_surface at 14.attach(wl_buffer at 27, 0, 0)
> > [1524849.730] wl_surface at 14.set_buffer_scale(1)
> > [1524849.821] wl_surface at 14.damage(0, 0, 750, 515)
> > <No commit yet, so drawing is attempted from older buffer that used to be
> >  attached to the surface, which happens to come from a destroyed pool,
> >  resulting it an invalid read from address 0xb5b2e000>
> > 
> > Signed-off-by: Lubomir Rintel <lkundrak at v3.sk>
> > ---
> > Hi,
> > 
> > This has been previously discussed in this thread:
> > http://lists.freedesktop.org/archives/wayland-devel/2013-November/012122.html
> > 
> > Pekka doesn't mind, Arnaud's suggestion does not seem doable.
> > Please let me know if there's anything else that should be done before this is 
> > merged.
> > 
> > Thank you!
> > Lubo
> > 
> >  src/pixman-renderer.c | 27 ++++++++++++++++++++++++++-
> >  1 file changed, 26 insertions(+), 1 deletion(-)
> > 
> > diff --git a/src/pixman-renderer.c b/src/pixman-renderer.c
> > index 5961965..1a1e6ae 100644
> > --- a/src/pixman-renderer.c
> > +++ b/src/pixman-renderer.c
> > @@ -42,6 +42,7 @@ struct pixman_surface_state {
> >  	pixman_image_t *image;
> >  	struct weston_buffer_reference buffer_ref;
> >  
> > +	struct wl_listener buffer_destroy_listener;
> >  	struct wl_listener surface_destroy_listener;
> >  	struct wl_listener renderer_destroy_listener;
> >  };
> > @@ -450,6 +451,22 @@ pixman_renderer_flush_damage(struct weston_surface *surface)
> >  }
> >  
> >  static void
> > +buffer_state_handle_buffer_destroy(struct wl_listener *listener, void *data)
> > +{
> > +	struct pixman_surface_state *ps;
> > +
> > +	ps = container_of(listener, struct pixman_surface_state,
> > +			  buffer_destroy_listener);
> > +
> > +	if (ps->image) {
> > +		pixman_image_unref(ps->image);
> > +		ps->image = NULL;
> > +	}
> > +
> > +	ps->buffer_destroy_listener.notify = NULL;
> > +}
> > +
> > +static void
> >  pixman_renderer_attach(struct weston_surface *es, struct weston_buffer *buffer)
> >  {
> >  	struct pixman_surface_state *ps = get_surface_state(es);
> > @@ -499,6 +516,13 @@ pixman_renderer_attach(struct weston_surface *es, struct weston_buffer *buffer)
> >  		buffer->width, buffer->height,
> >  		wl_shm_buffer_get_data(shm_buffer),
> >  		wl_shm_buffer_get_stride(shm_buffer));
> > +
> > +	if (ps->buffer_destroy_listener.notify)
> > +		wl_list_remove(&ps->buffer_destroy_listener.link);
> 
> We need to remove the old listener early in the function, before
> 
>         if (!buffer)
>                 return;
> 
> so that we also remove the listener if a NULL buffer is attached.

Why? There's no harm invoking the listener if a null buffer has been
reattached to a surface. It checks for actual presence for pixmap data
and still gets unhooked upon surface destroy. (Apart from that the code
might look a bit more elegant and the ps->image NULL check in the
listener might be unnecessary.)

> 
> Kristian
> 
> > +	ps->buffer_destroy_listener.notify =
> > +		buffer_state_handle_buffer_destroy;
> > +	wl_signal_add(&buffer->destroy_signal,
> > +		      &ps->buffer_destroy_listener);
> >  }
> >  
> >  static void
> > @@ -506,7 +530,8 @@ pixman_renderer_surface_state_destroy(struct pixman_surface_state *ps)
> >  {
> >  	wl_list_remove(&ps->surface_destroy_listener.link);
> >  	wl_list_remove(&ps->renderer_destroy_listener.link);
> > -
> > +	if (ps->buffer_destroy_listener.notify)
> > +		wl_list_remove(&ps->buffer_destroy_listener.link);
> >  
> >  	ps->surface->renderer_state = NULL;
> >  
> > -- 
> > 1.8.4.2
> > 
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