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

["Rémi Denis-Courmont" <remi@remlab.net>]

Le 19 juin 2024 14:34:59 GMT+02:00, James Almer <jamrial@gmail.com> a écrit :
>On 6/18/2024 4:07 AM, Rémi Denis-Courmont wrote:
>> 
>> 
>> Le 17 juin 2024 01:08:27 GMT+02:00, Michael Niedermayer <michael@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@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() one?

I'd rather the ckd_*() stuff but the differences are mostly stylistic.

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