[FFmpeg-devel] [PATCH 3/4] lavfi/nlmeans: Checking number precision when computing integral images

[mypopy at gmail.com]

On Wed, Mar 6, 2019 at 3:55 PM Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>
> 2019-03-06 4:18 GMT+01:00, Jun Zhao <mypopydev at gmail.com>:
> > From: Jun Zhao <barryjzhao at tencent.com>
> >
> > accumulation of 8-bits uint_8 (uint8_t *src) into 32-bits (uint32_t *ii)
> > data type, it will have a risk of an integral value becoming larger than
> > the 32-bits integer capacity and resulting in an integer overflow. For
> > this risk, add a checking with warning message.
> >
> > Signed-off-by: Jun Zhao <barryjzhao at tencent.com>
> > ---
> >  libavfilter/vf_nlmeans.c |    7 +++++++
> >  1 files changed, 7 insertions(+), 0 deletions(-)
> >
> > diff --git a/libavfilter/vf_nlmeans.c b/libavfilter/vf_nlmeans.c
> > index dcb5a03..31c8304 100644
> > --- a/libavfilter/vf_nlmeans.c
> > +++ b/libavfilter/vf_nlmeans.c
> > @@ -236,6 +236,13 @@ static void compute_ssd_integral_image(const
> > NLMeansDSPContext *dsp,
> >      // adjusted end x position of the safe area after width of the safe
> > area gets aligned
> >      const int endx_safe = startx_safe + safe_pw;
> >
> > +    // accumulation of 8-bits uint_8 (uint8_t *src) into 32-bits (uint32_t
> > *ii)
> > +    // data type, it will have a risk of an integral value becoming larger
> > than
> > +    // the 32-bits integer capacity and resulting in an integer overflow.
> > +    if ((w * h * UINT8_MAX) > UINT32_MAX)
>
> I don't think UINT8_MAX increases readability and I suspect
> this should contain "UINT32_MAX / (w*h)" or similar on
> one side.
>
You means like: UINT32_MAX/w < (UINT8_MAX * h) ?
> > +        av_log(NULL, AV_LOG_WARNING,
> > +               "image (%d x %d) integral value maybe overflow.\n", w ,h);
>
> may overflow?
Will update the warning message as the suggestion.Tks