[FFmpeg-devel] [PATCH 2/2] avcodec/h264: Check weight values to be within the specs limits.

[Michael Niedermayer]

On Wed, Mar 22, 2017 at 09:06:09AM -0400, Ronald S. Bultje wrote:
> Hi,
> 
> On Tue, Mar 21, 2017 at 9:59 PM, Michael Niedermayer <michael at niedermayer.cc
> > wrote:
> 
> > @@ -59,6 +59,9 @@ int ff_h264_pred_weight_table(GetBitContext *gb, const
> > SPS *sps,
> >              if (luma_weight_flag) {
> >                  pwt->luma_weight[i][list][0] = get_se_golomb(gb);
> >                  pwt->luma_weight[i][list][1] = get_se_golomb(gb);
> > +                if (   (int8_t)pwt->luma_weight[i][list][0] !=
> > pwt->luma_weight[i][list][0]
> > +                    || (int8_t)pwt->luma_weight[i][list][1] !=
> > pwt->luma_weight[i][list][1])
> > +                    goto error;
> >
> 
> Can we please put || on the line before? h264* and a very limited subset of
> other files in our codebase have always been an exception to the large
> majority of the codebase and it's about time we fix that [1].

i find putting the operators in the first column more readable
but if its preferred in the last, iam happy to change it.


> 
> It's interesting (I mean that in a positive way) how you use casting to
> check for the range. It's a little obscure, but it's OK.

yes, it caused me to pause to but it was the simplest way i saw to do
the check


> 
> +error:
> > +    avpriv_request_sample(logctx, "Out of range weight\n");
> > +    return AVERROR_INVALIDDATA;
> 
> 
> Same comment as previously in other, but related, threads: unless there is
> real, demonstrable evidence that this happens in real-world files, this is
> fuzz/corruption only and shouldn't be accompanied by an explicit log
> message. Just return AVERROR_INVALIDDATA directly and remove the goto/error
> message.

If there is "real, demonstrable evidence that this happens in real-world
files" then we would likely have a sample and not ask for one with
avpriv_request_sample()

I think its very plausible that a encoder would use a weight that is
outside the range. Printing something does make sense.


off topic, but i saw some spurious errors in h264s output that were
new, maybe i can reduce these.

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Concerning the gods, I have no means of knowing whether they exist or not
or of what sort they may be, because of the obscurity of the subject, and
the brevity of human life -- Protagoras
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