[FFmpeg-devel] [PATCH 4/4] avcodec/jpeg2000dec: Check PLT data somewhat

[Andreas Rheinhardt]

Michael Niedermayer:
> Fixes: Timeout (21sec -> 0.6sec)
> Fixes: 14134/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_JPEG2000_fuzzer-5768371078955008
> 
> 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/jpeg2000dec.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/jpeg2000dec.c b/libavcodec/jpeg2000dec.c
> index 9198cf87cb..62b0b1f9b7 100644
> --- a/libavcodec/jpeg2000dec.c
> +++ b/libavcodec/jpeg2000dec.c
> @@ -832,15 +832,21 @@ static uint8_t get_tlm(Jpeg2000DecoderContext *s, int n)
>  static uint8_t get_plt(Jpeg2000DecoderContext *s, int n)
>  {
>      int i;
> +    int v;
>  
>      av_log(s->avctx, AV_LOG_DEBUG,
>              "PLT marker at pos 0x%X\n", bytestream2_tell(&s->g) - 4);
>  
> +    if (n < 4)
> +        return AVERROR_INVALIDDATA;
> +
>      /*Zplt =*/ bytestream2_get_byte(&s->g);
>  
>      for (i = 0; i < n - 3; i++) {
> -        bytestream2_get_byte(&s->g);
> +        v = bytestream2_get_byte(&s->g);
>      }
> +    if (v & 0x80)
> +        return AVERROR_INVALIDDATA;
>  
>      return 0;
>  }
> 
get_tlm should probably return int as uint8_t can't hold the
AVERROR_INVALIDDATA. gcc gives Woverflow warnings because of that.

Currently, the return value of get_tlm is always >= 0 and so is the
return value of jpeg2000_read_main_headers and of
jpeg2000_decode_frame if one runs into the AVERROR_INVALIDDATA checks.
(I didn't test it, just took a quick glimpse at the code.)

- Andreas