[Spice-devel] [PATCH spice-server] fixup! dcc-send: remove useless pipe_item assignment pipe_item

[Frediano Ziglio]

> > 
> > On 7/4/19 12:33 PM, Frediano Ziglio wrote:
> > > Remove use-after-free introduced by
> > > a78a7d251042892182b158650291d19a85bbd6b1
> > > ---
> > >   server/dcc-send.c | 9 +++++----
> > >   1 file changed, 5 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/server/dcc-send.c b/server/dcc-send.c
> > > index 565a79f33..4582e3545 100644
> > > --- a/server/dcc-send.c
> > > +++ b/server/dcc-send.c
> > > @@ -725,7 +725,6 @@ static void
> > > red_pipe_replace_rendered_drawables_with_images(DisplayChannelClient
> > >           RedPipeItem *pipe_item = l->data;
> > >           Drawable *drawable;
> > >           RedDrawablePipeItem *dpi;
> > > -        RedImageItem *image;
> > >   
> > >           if (pipe_item->type != RED_PIPE_ITEM_TYPE_DRAW)
> > >               continue;
> > > @@ -745,14 +744,16 @@ static void
> > > red_pipe_replace_rendered_drawables_with_images(DisplayChannelClient
> > >               continue;
> > >           }
> > >   
> > > -        image = dcc_add_surface_area_image(dcc,
> > > drawable->red_drawable->surface_id,
> > > -
> > > &drawable->red_drawable->bbox,
> > > l, TRUE);
> > > +        dcc_add_surface_area_image(dcc,
> > > drawable->red_drawable->surface_id,
> > > +                                   &drawable->red_drawable->bbox, l,
> > > TRUE);
> > >           resent_surface_ids[num_resent] =
> > >           drawable->red_drawable->surface_id;
> > >           resent_areas[num_resent] = drawable->red_drawable->bbox;
> > >           num_resent++;
> > >   
> > > -        spice_assert(image);
> > > +        GList *image_pos = l->next;
> > 
> > l may be the queue tail, and in that case l->next would be
> > NULL, wouldn't it ?
> > 
> 
> No, dcc_add_surface_area_image add an element after l so l->next can't be
> NULL.
> 
> > > +        spice_assert(image_pos);
> > >           red_channel_client_pipe_remove_and_release_pos(RED_CHANNEL_CLIENT(dcc),
> > >           l);
> > > +        l = image_pos;
> > >       }
> > >   }
> > >   
> > > 
> > 
> > I solved it differently:
> > 
> > diff --git a/server/dcc-send.c b/server/dcc-send.c
> > index 84fa1be72..255e893f7 100644
> > --- a/server/dcc-send.c
> > +++ b/server/dcc-send.c
> > @@ -713,7 +713,7 @@ static void
> > red_pipe_replace_rendered_drawables_with_images(DisplayChannelClient
> >       int resent_surface_ids[MAX_PIPE_SIZE];
> >       SpiceRect resent_areas[MAX_PIPE_SIZE]; // not pointers since
> > drawables may be released
> >       int num_resent;
> > -    GList *l;
> > +    GList *l, *lprev;
> 
> I would use just "prev" or "l_prev".
> 
> >       GQueue *pipe;
> > 
> >       resent_surface_ids[0] = first_surface_id;
> > @@ -723,12 +723,13 @@ static void
> > red_pipe_replace_rendered_drawables_with_images(DisplayChannelClient
> >       pipe = red_channel_client_get_pipe(RED_CHANNEL_CLIENT(dcc));
> > 
> >       // going from the oldest to the newest
> > -    for (l = pipe->tail; l != NULL; l = l->prev) {
> > +    for (l = pipe->tail; l != NULL; l = lprev) {
> >           RedPipeItem *pipe_item = l->data;
> >           Drawable *drawable;
> >           RedDrawablePipeItem *dpi;
> >           RedImageItem *image;
> > 
> > +        lprev = l->prev;
> >           if (pipe_item->type != RED_PIPE_ITEM_TYPE_DRAW)
> >               continue;
> >           dpi = SPICE_UPCAST(RedDrawablePipeItem, pipe_item);
> > 
> > 
> > 
> > 
> > Uri.
> > 
> 
> Fine with it.
> Or maybe you can update "l" directly and use a "curr" instead with
> limited scope (inside the "for") and always initialized?
> 

Why not using GLIST_FOREACH_REVERSED ?

Frediano