[FFmpeg-devel] [PATCH] avformat/iamf_parse: increase PutBytes buffer when writing AAC extradata

[Michael Niedermayer]

On Sat, May 10, 2025 at 12:51:09PM -0300, James Almer wrote:
> We may write up to 43 bits, so 5 bytes is not enough.
> 
> Fixes: Assertion n>=0 && n<=32 failed at ./libavcodec/get_bits.h:406
> Fixes: 398527871/clusterfuzz-testcase-minimized-ffmpeg_dem_IAMF_fuzzer-6602025714647040
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
>  libavformat/iamf_parse.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavformat/iamf_parse.c b/libavformat/iamf_parse.c
> index abedfdb066..14b69855c9 100644
> --- a/libavformat/iamf_parse.c
> +++ b/libavformat/iamf_parse.c
> @@ -285,7 +285,7 @@ static int update_extradata(AVCodecParameters *codecpar)
>          AV_WL16A(codecpar->extradata + 16, AV_RB16A(codecpar->extradata + 16)); // Byte swap Output Gain
>          break;
>      case AV_CODEC_ID_AAC: {
> -        uint8_t buf[5];
> +        uint8_t buf[6];

fails fate (with assertions enabled)

  libavutil      60.  2.100 / 60.  2.100
  libavcodec     62.  3.101 / 62.  3.101
  libavformat    62.  0.102 / 62.  0.102
  libavdevice    62.  0.100 / 62.  0.100
  libavfilter    11.  0.100 / 11.  0.100
  libswscale      9.  0.100 /  9.  0.100
  libswresample   6.  0.100 /  6.  0.100
Assertion n>=0 && n<=32 failed at ./libavcodec/get_bits.h:406
Aborted (core dumped)
threads=1
make: *** [tests/Makefile:316: fate-iamf-stereo-demux] Error 134


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

He who knows, does not speak. He who speaks, does not know. -- Lao Tsu
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