Re: [FFmpeg-devel] [PATCH 1/4] avcodec/vvc/vvc_ps: Check before access

[Nuo Mi <nuomi2021@gmail.com>]

On Tue, Feb 20, 2024 at 7:24 AM Andreas Rheinhardt <
andreas.rheinhardt@outlook.com> wrote:

> Andreas Rheinhardt:
> > max_bin_idx can be at most LMCS_MAX_BIN_SIZE - 1 here,
> > so pivot[LCMS_MAX_BIN_SIZE + 1] may be accessed,
> > but pivot has only LCMS_MAX_BIN_SIZE + 1 elements
> > (unless the values of pivot were so that it is always
> > assured that pivot[LCMS_MAX_BIN_SIZE] is always < sample
> > (which it is iff it is always < 2^bit_depth - 1)).
> > So reorder the checks.
> >
> > Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
> > ---
> > I don't know whether this can be triggered at all.
> >
> >  libavcodec/vvc/vvc_ps.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/libavcodec/vvc/vvc_ps.c b/libavcodec/vvc/vvc_ps.c
> > index 53a86321d6..376027ed81 100644
> > --- a/libavcodec/vvc/vvc_ps.c
> > +++ b/libavcodec/vvc/vvc_ps.c
> > @@ -652,7 +652,7 @@ static int lmcs_derive_lut(VVCLMCS *lmcs, const
> H266RawAPS *rlmcs, const H266Raw
> >      i = lmcs->min_bin_idx;
> >      for (uint16_t sample = 0; sample < max; sample++) {
> >          uint16_t inv_sample;
> > -        while (sample >= lmcs->pivot[i + 1] && i <= lmcs->max_bin_idx)
> > +        while (i <= lmcs->max_bin_idx && sample >= lmcs->pivot[i + 1])
> >              i++;
> >
> >          inv_sample = lmcs_derive_lut_sample(sample, input_pivot,
> lmcs->pivot,
>
> Will apply this patchset tomorrow unless there are objections.

LGTM for the enitre patchset.
Thank you, Andreas!

>


> - Andreas
>
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