[FFmpeg-devel] [PATCH 1/3] avcodec/cbs_h265_syntax_template: Check inter_ref_pic_set_prediction_flag

James Almer jamrial at gmail.com
Sat Jun 6 20:12:21 EEST 2020


On 6/6/2020 1:12 PM, James Almer wrote:
> On 6/6/2020 1:03 PM, Michael Niedermayer wrote:
>> Fixes: out of array access
>> Fixes: 23034/clusterfuzz-testcase-minimized-ffmpeg_BSF_HEVC_METADATA_fuzzer-5074645169733632.fuzz
>>
>> 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/cbs_h265_syntax_template.c | 5 ++++-
>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/libavcodec/cbs_h265_syntax_template.c b/libavcodec/cbs_h265_syntax_template.c
>> index 5b7d1aa837..900764a3cf 100644
>> --- a/libavcodec/cbs_h265_syntax_template.c
>> +++ b/libavcodec/cbs_h265_syntax_template.c
>> @@ -518,8 +518,11 @@ static int FUNC(st_ref_pic_set)(CodedBitstreamContext *ctx, RWContext *rw,
>>  
>>      if (st_rps_idx != 0)
>>          flag(inter_ref_pic_set_prediction_flag);
>> -    else
>> +    else {
>>          infer(inter_ref_pic_set_prediction_flag, 0);
>> +        if (current->inter_ref_pic_set_prediction_flag)
> 
> This makes no sense. The infer(inter_ref_pic_set_prediction_flag, 0)
> line sets current->inter_ref_pic_set_prediction_flag to 0. How can this
> check even succeed?
> 
> Can you give some context?

Oh, i guess this is during writing, not reading, where you just get a
warning about mismatching values.

Sounds like the bug is elsewhere, then, seeing
inter_ref_pic_set_prediction_flag was set to 1 in an scenario where it
should have been 0.

> 
>> +            return AVERROR_INVALIDDATA;
>> +    }
>>  
>>      if (current->inter_ref_pic_set_prediction_flag) {
>>          unsigned int ref_rps_idx, num_delta_pocs, num_ref_pics;
>>
> 



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