[FFmpeg-devel] [PATCH 3/4] avcodec/vp568: Check that there is enough data for ff_vp56_init_range_decoder()

[Michael Niedermayer]

On Tue, Mar 07, 2017 at 08:35:33AM -0500, Ronald S. Bultje wrote:
> Hi,
> 
> On Mon, Mar 6, 2017 at 8:41 PM, Michael Niedermayer <michael at niedermayer.cc>
> wrote:
> 
> > -void ff_vp56_init_range_decoder(VP56RangeCoder *c, const uint8_t *buf,
> > int buf_size)
> > +int ff_vp56_init_range_decoder(VP56RangeCoder *c, const uint8_t *buf,
> > int buf_size)
> >  {
> >      c->high = 255;
> >      c->bits = -16;
> >      c->buffer = buf;
> >      c->end = buf + buf_size;
> > +    if (buf_size < 1)
> > +        return AVERROR_INVALIDDATA;
> >      c->code_word = bytestream_get_be24(&c->buffer);
> > +    return 0;
> >  }
> 
> 
> Isn't this AV_INPUT_BUFFER_PADDING_SIZE?

There was no out of array access, the issue was that the code spend
alot of time doing nothing as a result of 0 bytes input being turned
into 16bits of available data repeatly.

I intended to suggest to adjust the 16 to 8 on a 1 byte buf_size
subsequently

> 
> And this is inconsistent with the silent failure in renorm().

testing each use of renorm likely would cause a speed loss, such
a failure should be caught by the explicit end of bitstream checks
on the other loops

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I do not agree with what you have to say, but I'll defend to the death your
right to say it. -- Voltaire
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