Re: [FFmpeg-devel] [PATCH 2/9] avcodec/mpeg4audio: Check that there is enough space for the first 3 elements in ff_mpeg4audio_get_config_gb()

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Michael Niedermayer:
> Fixes: out of array access
> Fixes: 68863/clusterfuzz-testcase-minimized-ffmpeg_dem_IAMF_fuzzer-4833546039525376
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavcodec/mpeg4audio.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/libavcodec/mpeg4audio.c b/libavcodec/mpeg4audio.c
> index fbd2a8f811a..ae18944f0d5 100644
> --- a/libavcodec/mpeg4audio.c
> +++ b/libavcodec/mpeg4audio.c
> @@ -94,6 +94,10 @@ int ff_mpeg4audio_get_config_gb(MPEG4AudioConfig *c, GetBitContext *gb,
>  {
>      int specific_config_bitindex, ret;
>      int start_bit_index = get_bits_count(gb);
> +
> +    if (get_bits_left(gb) < 5+4+4)
> +        return AVERROR_INVALIDDATA;
> +
>      c->object_type = get_object_type(gb);
>      c->sample_rate = get_sample_rate(gb, &c->sampling_index);
>      c->chan_config = get_bits(gb, 4);

This is not a proper fix. The real bug seems to be that
avpriv_mpeg4audio_get_config2() relies on the buffer to be padded, but
iamf_parse.c does not add padding.

- Andreas

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