[FFmpeg-devel] [PATCH 1/3] avcodec/hevc_sei: check size before using it

[lance.lmwang at gmail.com]

On Tue, Sep 14, 2021 at 07:27:04PM +0800, mypopy at gmail.com wrote:
> On Tue, Sep 14, 2021 at 6:50 PM <lance.lmwang at gmail.com> wrote:
> >
> > From: Limin Wang <lance.lmwang at gmail.com>
> >
> > Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> > ---
> >  libavcodec/hevc_sei.c | 31 +++++++++++++++++++++++++------
> >  1 file changed, 25 insertions(+), 6 deletions(-)
> >
> > diff --git a/libavcodec/hevc_sei.c b/libavcodec/hevc_sei.c
> > index 2c326bf..29d0346 100644
> > --- a/libavcodec/hevc_sei.c
> > +++ b/libavcodec/hevc_sei.c
> > @@ -52,9 +52,13 @@ static int decode_nal_sei_decoded_picture_hash(HEVCSEIPictureHash *s, GetBitCont
> >      return 0;
> >  }
> >
> > -static int decode_nal_sei_mastering_display_info(HEVCSEIMasteringDisplay *s, GetBitContext *gb)
> > +static int decode_nal_sei_mastering_display_info(HEVCSEIMasteringDisplay *s, GetBitContext *gb, int size)
> >  {
> >      int i;
> > +
> > +    if (size < 24)
> > +        return AVERROR_INVALIDDATA;
> > +
> I can't find more information about this change, is it the old code
> leading some issue?

By the standard, it's 24 byte for this sei, but the bitstream data may be corrupt. So it's better to check the
size before use it.


> 
> >      // Mastering primaries
> >      for (i = 0; i < 3; i++) {
> >          s->display_primaries[i][0] = get_bits(gb, 16);
> > @@ -67,23 +71,32 @@ static int decode_nal_sei_mastering_display_info(HEVCSEIMasteringDisplay *s, Get
> >      // Max and min luminance of mastering display
> >      s->max_luminance = get_bits_long(gb, 32);
> >      s->min_luminance = get_bits_long(gb, 32);
> > +    size -= 24;
> >
> >      // As this SEI message comes before the first frame that references it,
> >      // initialize the flag to 2 and decrement on IRAP access unit so it
> >      // persists for the coded video sequence (e.g., between two IRAPs)
> >      s->present = 2;
> > +
> > +    skip_bits_long(gb, 8 * size);
> >      return 0;
> >  }
> >
> > -static int decode_nal_sei_content_light_info(HEVCSEIContentLight *s, GetBitContext *gb)
> > +static int decode_nal_sei_content_light_info(HEVCSEIContentLight *s, GetBitContext *gb, int size)
> >  {
> > +    if (size < 4)
> > +        return AVERROR_INVALIDDATA;
> > +
> >      // Max and average light levels
> >      s->max_content_light_level     = get_bits(gb, 16);
> >      s->max_pic_average_light_level = get_bits(gb, 16);
> > +    size -= 4;
> >      // As this SEI message comes before the first frame that references it,
> >      // initialize the flag to 2 and decrement on IRAP access unit so it
> >      // persists for the coded video sequence (e.g., between two IRAPs)
> >      s->present = 2;
> > +
> > +    skip_bits_long(gb, 8 * size);
> >      return  0;
> >  }
> >
> > @@ -342,10 +355,16 @@ static int decode_nal_sei_active_parameter_sets(HEVCSEI *s, GetBitContext *gb, v
> >      return 0;
> >  }
> >
> > -static int decode_nal_sei_alternative_transfer(HEVCSEIAlternativeTransfer *s, GetBitContext *gb)
> > +static int decode_nal_sei_alternative_transfer(HEVCSEIAlternativeTransfer *s, GetBitContext *gb, int size)
> >  {
> > +    if (size < 1)
> > +        return AVERROR_INVALIDDATA;
> > +
> >      s->present = 1;
> >      s->preferred_transfer_characteristics = get_bits(gb, 8);
> > +    size--;
> > +
> > +    skip_bits_long(gb, 8 * size);
> >      return 0;
> >  }
> >
> > @@ -451,9 +470,9 @@ static int decode_nal_sei_prefix(GetBitContext *gb, void *logctx, HEVCSEI *s,
> >      case SEI_TYPE_PIC_TIMING:
> >          return decode_nal_sei_pic_timing(s, gb, ps, logctx, size);
> >      case SEI_TYPE_MASTERING_DISPLAY_COLOUR_VOLUME:
> > -        return decode_nal_sei_mastering_display_info(&s->mastering_display, gb);
> > +        return decode_nal_sei_mastering_display_info(&s->mastering_display, gb, size);
> >      case SEI_TYPE_CONTENT_LIGHT_LEVEL_INFO:
> > -        return decode_nal_sei_content_light_info(&s->content_light, gb);
> > +        return decode_nal_sei_content_light_info(&s->content_light, gb, size);
> >      case SEI_TYPE_ACTIVE_PARAMETER_SETS:
> >          return decode_nal_sei_active_parameter_sets(s, gb, logctx);
> >      case SEI_TYPE_USER_DATA_REGISTERED_ITU_T_T35:
> > @@ -461,7 +480,7 @@ static int decode_nal_sei_prefix(GetBitContext *gb, void *logctx, HEVCSEI *s,
> >      case SEI_TYPE_USER_DATA_UNREGISTERED:
> >          return decode_nal_sei_user_data_unregistered(&s->unregistered, gb, size);
> >      case SEI_TYPE_ALTERNATIVE_TRANSFER_CHARACTERISTICS:
> > -        return decode_nal_sei_alternative_transfer(&s->alternative_transfer, gb);
> > +        return decode_nal_sei_alternative_transfer(&s->alternative_transfer, gb, size);
> >      case SEI_TYPE_TIME_CODE:
> >          return decode_nal_sei_timecode(&s->timecode, gb);
> >      case SEI_TYPE_FILM_GRAIN_CHARACTERISTICS:
> > --
> > 1.8.3.1
> >
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> 
> 
> 
> -- 
> =======================================
> Jun zhao/赵军
> +++++++++++++++++++++++++++++++++++++++

-- 
Thanks,
Limin Wang