[FFmpeg-devel] [PATCH 2/2] avcodec/arbc: Use ff_reget_buffer()

[Michael Niedermayer]

On Fri, Aug 30, 2019 at 11:15:21AM -0300, James Almer wrote:
> On 8/29/2019 4:33 PM, James Almer wrote:
> > On 8/29/2019 4:04 PM, Michael Niedermayer wrote:
> >> Fixes: Timeout (20sec -> 0.5sec)
> >> Fixes: 16404/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ARBC_fuzzer-5660216355454976
> >>
> >> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> >> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> >> ---
> >>  libavcodec/arbc.c | 21 +++++++--------------
> >>  1 file changed, 7 insertions(+), 14 deletions(-)
> >>
> >> diff --git a/libavcodec/arbc.c b/libavcodec/arbc.c
> >> index 06970f140b..f0de50e243 100644
> >> --- a/libavcodec/arbc.c
> >> +++ b/libavcodec/arbc.c
> >> @@ -136,15 +136,9 @@ static int decode_frame(AVCodecContext *avctx, void *data,
> >>      if (7 * nb_segments > bytestream2_get_bytes_left(&s->gb))
> >>          return AVERROR_INVALIDDATA;
> >>  
> >> -    if ((ret = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0)
> >> +    if ((ret = ff_reget_buffer(avctx, s->prev_frame)) < 0)
> >>          return ret;
> >>  
> >> -    if (s->prev_frame->data[0]) {
> >> -        ret = av_frame_copy(frame, s->prev_frame);
> >> -        if (ret < 0)
> >> -            return ret;
> >> -    }
> >> -
> >>      for (int i = 0; i < nb_segments; i++) {
> >>          int resolution_flag;
> >>          int fill;
> >> @@ -161,19 +155,18 @@ static int decode_frame(AVCodecContext *avctx, void *data,
> >>          resolution_flag = bytestream2_get_byte(&s->gb);
> >>  
> >>          if (resolution_flag & 0x10)
> >> -            prev_pixels -= fill_tileX(avctx, 1024, 1024, fill, frame);
> >> +            prev_pixels -= fill_tileX(avctx, 1024, 1024, fill, s->prev_frame);
> >>          if (resolution_flag & 0x08)
> >> -            prev_pixels -= fill_tileX(avctx, 256, 256, fill, frame);
> >> +            prev_pixels -= fill_tileX(avctx, 256, 256, fill, s->prev_frame);
> >>          if (resolution_flag & 0x04)
> >> -            prev_pixels -= fill_tileX(avctx, 64, 64, fill, frame);
> >> +            prev_pixels -= fill_tileX(avctx, 64, 64, fill, s->prev_frame);
> >>          if (resolution_flag & 0x02)
> >> -            prev_pixels -= fill_tileX(avctx, 16, 16, fill, frame);
> >> +            prev_pixels -= fill_tileX(avctx, 16, 16, fill, s->prev_frame);
> >>          if (resolution_flag & 0x01)
> >> -            prev_pixels -= fill_tile4(avctx, fill, frame);
> >> +            prev_pixels -= fill_tile4(avctx, fill, s->prev_frame);
> >>      }
> >>  
> >> -    av_frame_unref(s->prev_frame);
> >> -    if ((ret = av_frame_ref(s->prev_frame, frame)) < 0)
> >> +    if ((ret = av_frame_ref(frame, s->prev_frame)) < 0)
> >>          return ret;
> >>  
> >>      frame->pict_type = prev_pixels <= 0 ? AV_PICTURE_TYPE_I : AV_PICTURE_TYPE_P;
> > 
> > You could while at it revert 8b10f09fd53, then implement d70bbdc5fa for
> > this decoder as part of this patch.
> 
> Or maybe we should do what you suggested and simplify things by either
> adding a new reget function, or changing the current one to take a new
> argument to request a writable buffer.

> The latter sounds better, IMO, and I can look into implementing it.

sure, ok

thx

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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