[FFmpeg-devel] [PATCH]lavc/h264_ps: Check chroma_location limits

[wm4]

On Fri, 24 Mar 2017 11:23:44 +0100
Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:

> 2017-03-24 10:59 GMT+01:00 wm4 <nfxjfg at googlemail.com>:
> > On Fri, 24 Mar 2017 10:40:21 +0100
> > Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
> >  
> >> From 1c249440c62271565be12112f321ad9aa6a922fb Mon Sep 17 00:00:00 2001
> >> From: Carl Eugen Hoyos <cehoyos at ag.or.at>
> >> Date: Fri, 24 Mar 2017 10:38:22 +0100
> >> Subject: [PATCH] lavc/h264_ps: Check that chroma_location is within limits.
> >>
> >> Fixes ticket #6255.
> >> ---
> >>  libavcodec/h264_ps.c |    2 ++
> >>  1 file changed, 2 insertions(+)
> >>
> >> diff --git a/libavcodec/h264_ps.c b/libavcodec/h264_ps.c
> >> index b78ad25..55e6a6e 100644
> >> --- a/libavcodec/h264_ps.c
> >> +++ b/libavcodec/h264_ps.c
> >> @@ -181,6 +181,8 @@ static inline int decode_vui_parameters(GetBitContext *gb, AVCodecContext *avctx
> >>      if (get_bits1(gb)) {
> >>          /* chroma_sample_location_type_top_field */
> >>          avctx->chroma_sample_location = get_ue_golomb(gb) + 1;
> >> +        if (avctx->chroma_sample_location >= AVCHROMA_LOC_NB)
> >> +            avctx->chroma_sample_location = AVCHROMA_LOC_UNSPECIFIED;  
> >
> > AVCHROMA_LOC_NB is not part of the libavutil ABI, so libavcodec can in
> > theory not use it.  
> 
> I suspect you misread this rule (we cannot make _NB smaller), in any case
> please look a few lines up from the patch, there are several similar
> cases there.

Quoting the source code:

    AVCHROMA_LOC_NB               ///< Not part of ABI

Seems pretty clear.