Re: [PATCH] ui/gtk: fix NULL pointer dereference

[Christian Schoenebeck <qemu_oss@crudebyte.com>]

On Montag, 8. März 2021 04:45:24 CET Akihiko Odaki wrote:
> 2021年3月8日(月) 4:57 Christian Schoenebeck <qemu_oss@crudebyte.com>:
> > DisplaySurface pointer passed to gd_switch() can be NULL, so check this
> > before trying to dereference it.
> > 
> > Fixes: c821a58ee7 ("ui/console: Pass placeholder surface to display")
> > Reported-by: Coverity (CID 1448421)
> > Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
> > ---
> > 
> >  ui/gtk.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/ui/gtk.c b/ui/gtk.c
> > index 3edaf041de..a27b27d004 100644
> > --- a/ui/gtk.c
> > +++ b/ui/gtk.c
> > @@ -567,7 +567,7 @@ static void gd_switch(DisplayChangeListener *dcl,
> > 
> >      }
> >      vc->gfx.ds = surface;
> > 
> > -    if (surface->format == PIXMAN_x8r8g8b8) {
> > +    if (surface && surface->format == PIXMAN_x8r8g8b8) {
> > 
> >          /*
> >          
> >           * PIXMAN_x8r8g8b8 == CAIRO_FORMAT_RGB24
> >           *
> > 
> > @@ -580,7 +580,7 @@ static void gd_switch(DisplayChangeListener *dcl,
> > 
> >               surface_width(surface),
> >               surface_height(surface),
> >               surface_stride(surface));
> > 
> > -    } else {
> > +    } else if (surface) {
> > 
> >          /* Must convert surface, use pixman to do it. */
> >          vc->gfx.convert = pixman_image_create_bits(PIXMAN_x8r8g8b8,
> >          
> >                                                     surface_width(surface)
> >                                                     ,
> > 
> > --
> > 2.20.1
> 
> When will the DisplaySurface pointer passed to gd_switch() be NULL?
> Also, it affects other displays so it should be fixed in ui/console.c,
> or fix all relevant displays.

This was just about silencing the mentioned automated Coverity defects report.
If you have a better solution, then just ignore this patch.

Best regards,
Christian Schoenebeck