[FFmpeg-devel] [PATCH 5/9] avformat/mov: Check extend and base offset

[James Almer]

On 6/18/2024 4:07 AM, Rémi Denis-Courmont wrote:
> 
> 
> Le 17 juin 2024 01:08:27 GMT+02:00, Michael Niedermayer <michael at niedermayer.cc> a écrit :
>> Fixes: signed integer overflow: 2314885530818453536 + 9151314442816847872 cannot be represented in type 'long'
>> Fixes: 68359/clusterfuzz-testcase-minimized-ffmpeg_dem_MOV_fuzzer-6571950311800832
>>
>> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
>> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
>> ---
>> libavformat/mov.c | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/libavformat/mov.c b/libavformat/mov.c
>> index 9016cd5ad08..46cbce98040 100644
>> --- a/libavformat/mov.c
>> +++ b/libavformat/mov.c
>> @@ -8131,7 +8131,9 @@ static int mov_read_iloc(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>>          }
>>          for (int j = 0; j < extent_count; j++) {
>>              if (rb_size(pb, &extent_offset, offset_size) < 0 ||
>> -                rb_size(pb, &extent_length, length_size) < 0)
>> +                rb_size(pb, &extent_length, length_size) < 0 ||
>> +                base_offset < 0 || extent_offset < 0 ||
>> +                base_offset + (uint64_t)extent_offset > INT64_MAX)
> 
> Can we please stop with the bespoke arithmetic overflow checks and add dedicated helpers instead, similar to what GCC and C23 have?

You mean the __builtin_*_overflow() ones?

> 
>>                  return AVERROR_INVALIDDATA;
>>              if (offset_type == 1)
>>                  c->heif_item[i].is_idat_relative = 1;
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