On 11/10, Arthur Grillo wrote:
>
>
> On 08/11/23 13:36, Harry Wentland wrote:
> > When the floor LUT index (drm_fixp2int(lut_index) is the last
> > index of the array the ceil LUT index will point to an entry
> > beyond the array. Make sure we guard against it and use the
> > value of the floor LUT index.
> >
> > v3:
> > - Drop bits from commit description that didn't contribute
> > anything of value
> >
> > Signed-off-by: Harry Wentland <harry.wentland@xxxxxxx>
> > Cc: Arthur Grillo <arthurgrillo@xxxxxxxxxx>
>
> LGTM
> Reviewed-by: Arthur Grillo <arthurgrillo@xxxxxxxxxx>
Nice catch. Thanks!
I'll already apply this one to drm-misc-next too.
CC'ing other VKMS maintainers/reviewers.
Melissa
>
> Best Regards,
> ~Arthur Grillo
>
> > ---
> > drivers/gpu/drm/vkms/vkms_composer.c | 14 ++++++++++----
> > 1 file changed, 10 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> > index 6f942896036e..25b6b73bece8 100644
> > --- a/drivers/gpu/drm/vkms/vkms_composer.c
> > +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> > @@ -123,6 +123,8 @@ static u16 apply_lut_to_channel_value(const struct vkms_color_lut *lut, u16 chan
> > enum lut_channel channel)
> > {
> > s64 lut_index = get_lut_index(lut, channel_value);
> > + u16 *floor_lut_value, *ceil_lut_value;
> > + u16 floor_channel_value, ceil_channel_value;
> >
> > /*
> > * This checks if `struct drm_color_lut` has any gap added by the compiler
> > @@ -130,11 +132,15 @@ static u16 apply_lut_to_channel_value(const struct vkms_color_lut *lut, u16 chan
> > */
> > static_assert(sizeof(struct drm_color_lut) == sizeof(__u16) * 4);
> >
> > - u16 *floor_lut_value = (__u16 *)&lut->base[drm_fixp2int(lut_index)];
> > - u16 *ceil_lut_value = (__u16 *)&lut->base[drm_fixp2int_ceil(lut_index)];
> > + floor_lut_value = (__u16 *)&lut->base[drm_fixp2int(lut_index)];
> > + if (drm_fixp2int(lut_index) == (lut->lut_length - 1))
> > + /* We're at the end of the LUT array, use same value for ceil and floor */
> > + ceil_lut_value = floor_lut_value;
> > + else
> > + ceil_lut_value = (__u16 *)&lut->base[drm_fixp2int_ceil(lut_index)];
> >
> > - u16 floor_channel_value = floor_lut_value[channel];
> > - u16 ceil_channel_value = ceil_lut_value[channel];
> > + floor_channel_value = floor_lut_value[channel];
> > + ceil_channel_value = ceil_lut_value[channel];
> >
> > return lerp_u16(floor_channel_value, ceil_channel_value,
> > lut_index & DRM_FIXED_DECIMAL_MASK);
