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

[Andreas Rheinhardt]

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
> 
get_plt, not get_tlm. Sorry.

- Andreas