[FFmpeg-devel] [PATCH 1/3] avcodec/h2645_parse: Limit initial skipped_bytes_pos_size to nal size / 16

[James Almer]

On 10/4/2020 4:41 PM, Michael Niedermayer wrote:
> 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: Michael Niedermayer <michael at niedermayer.cc>
> ---
>  libavcodec/h2645_parse.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavcodec/h2645_parse.c b/libavcodec/h2645_parse.c
> index 0f98b49fbe..61105a6eb5 100644
> --- a/libavcodec/h2645_parse.c
> +++ b/libavcodec/h2645_parse.c
> @@ -467,7 +467,7 @@ int ff_h2645_packet_split(H2645Packet *pkt, const uint8_t *buf, int length,
>              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_size = FFMIN(1024, 1+(extract_length>>4)); // initial buffer size

Why is there even an initial buffer? Why not just let
ff_h2645_extract_rbsp() allocate it when needed?

You could even replace the av_reallocp_array() call there that doubles
the buffer size each time with an av_fast_realloc(). Should also help
with memory usage.

>              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);
>