[FFmpeg-devel] [PATCH] avcodec/h2645_parse: remove initial skipped_bytes_pos buffer

Andreas Rheinhardt andreas.rheinhardt at gmail.com
Sat Oct 10 01:43:53 EEST 2020


James Almer:
> Allocate it only when it's needed.
> 
> Fixes: OOM
> Fixes: 23817/clusterfuzz-testcase-minimized-ffmpeg_BSF_H264_METADATA_fuzzer-6300869057576960
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
>  libavcodec/h2645_parse.c | 28 ++++++++++------------------
>  1 file changed, 10 insertions(+), 18 deletions(-)
> 
> diff --git a/libavcodec/h2645_parse.c b/libavcodec/h2645_parse.c
> index 0f98b49fbe..929fb34eef 100644
> --- a/libavcodec/h2645_parse.c
> +++ b/libavcodec/h2645_parse.c
> @@ -108,22 +108,20 @@ int ff_h2645_extract_rbsp(const uint8_t *src, int length,
>                  dst[di++] = 0;
>                  si       += 3;
>  
> -                if (nal->skipped_bytes_pos) {
> -                    nal->skipped_bytes++;
> -                    if (nal->skipped_bytes_pos_size < nal->skipped_bytes) {
> -                        nal->skipped_bytes_pos_size *= 2;
> -                        av_assert0(nal->skipped_bytes_pos_size >= nal->skipped_bytes);
> -                        av_reallocp_array(&nal->skipped_bytes_pos,
> +                nal->skipped_bytes++;
> +                if (nal->skipped_bytes_pos_size < nal->skipped_bytes) {
> +                    nal->skipped_bytes_pos_size = nal->skipped_bytes * 2;
> +                    av_assert0(nal->skipped_bytes_pos_size >= nal->skipped_bytes);
> +                    av_reallocp_array(&nal->skipped_bytes_pos,
>                                  nal->skipped_bytes_pos_size,
>                                  sizeof(*nal->skipped_bytes_pos));
> -                        if (!nal->skipped_bytes_pos) {
> -                            nal->skipped_bytes_pos_size = 0;
> -                            return AVERROR(ENOMEM);
> -                        }
> +                    if (!nal->skipped_bytes_pos) {
> +                        nal->skipped_bytes_pos_size = 0;
> +                        return AVERROR(ENOMEM);
>                      }
> -                    if (nal->skipped_bytes_pos)
> -                        nal->skipped_bytes_pos[nal->skipped_bytes-1] = di - 1;
>                  }
> +                if (nal->skipped_bytes_pos)
> +                    nal->skipped_bytes_pos[nal->skipped_bytes-1] = di - 1;
>                  continue;
>              } else // next start code
>                  goto nsc;
> @@ -466,12 +464,6 @@ int ff_h2645_packet_split(H2645Packet *pkt, const uint8_t *buf, int length,
>              pkt->nals = tmp;
>              memset(pkt->nals + pkt->nals_allocated, 0, sizeof(*pkt->nals));
>  
> -            nal = &pkt->nals[pkt->nb_nals];
> -            nal->skipped_bytes_pos_size = 1024; // initial buffer size
> -            nal->skipped_bytes_pos = av_malloc_array(nal->skipped_bytes_pos_size, sizeof(*nal->skipped_bytes_pos));
> -            if (!nal->skipped_bytes_pos)
> -                return AVERROR(ENOMEM);
> -
>              pkt->nals_allocated = new_size;
>          }
>          nal = &pkt->nals[pkt->nb_nals];
> 
This has the disadvantage that it always keeps the position of the 0x03
even when the caller does not want it; most callers don't want it, the
only exception is the HEVC decoder. Your patch will lead to memleaks for
the users that use ff_h2645_extract_rbsp() directly.

- Andreas


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