On 02/10/16 17:17, Paolo Bonzini wrote:
> The "max" value is being compared with >=, but addr + width points to
> the first byte that will _not_ be copied. Laszlo suggested using a
> "greater than" comparison, instead of subtracting one like it is
> already done above for the height, so that max remains always positive.
>
> The mistake is "safe"---it will reject some blits, but will never cause
> out-of-bounds writes.
>
> Cc: Gerd Hoffmann <kra...@redhat.com>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> hw/display/cirrus_vga.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c
> index b6ce1c8..57b91a7 100644
> --- a/hw/display/cirrus_vga.c
> +++ b/hw/display/cirrus_vga.c
> @@ -276,14 +276,14 @@ static bool blit_region_is_unsafe(struct CirrusVGAState
> *s,
> + ((int64_t)s->cirrus_blt_height-1) * pitch;
> int32_t max = addr
> + s->cirrus_blt_width;
> - if (min < 0 || max >= s->vga.vram_size) {
> + if (min < 0 || max > s->vga.vram_size) {
> return true;
> }
> } else {
> int64_t max = addr
> + ((int64_t)s->cirrus_blt_height-1) * pitch
> + s->cirrus_blt_width;
> - if (max >= s->vga.vram_size) {
> + if (max > s->vga.vram_size) {
> return true;
> }
> }
>
Thank you for your patience. :)
Reviewed-by: Laszlo Ersek <ler...@redhat.com>
