Re: [PATCH 03/12] macfb: fix overflow of color_palette array

[Laurent Vivier]

Le 02/10/2021 à 12:59, Mark Cave-Ayland a écrit :
> The palette_current index counter has a maximum size of 256 * 3 to cover a 
> full
> color palette of 256 RGB entries. Linux assumes that the palette_current index
> wraps back around to zero after writing 256 RGB entries so ensure that
> palette_current is reset at this point to prevent data corruption within
> MacfbState.
> 
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>  hw/display/macfb.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/hw/display/macfb.c b/hw/display/macfb.c
> index 815870f2fe..f4e789d0d7 100644
> --- a/hw/display/macfb.c
> +++ b/hw/display/macfb.c
> @@ -307,6 +307,9 @@ static void macfb_ctrl_write(void *opaque,
>          if (s->palette_current % 3) {
>              macfb_invalidate_display(s);
>          }
> +        if (s->palette_current >= sizeof(s->color_palette)) {
> +            s->palette_current = 0;
> +        }
>          break;
>      }
>  }
> 

What about "s->palette_current = (s->palette_current + 1) % 
sizeof(s->color_palette)"?

Thanks,
Laurent