Re: [FFmpeg-devel] [PATCH 3/3] avformat/iamf_parse: check space left for AAC

From: James Almer <jamrial@gmail.com>
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH 3/3] avformat/iamf_parse: check space left for AAC
Date: Sat, 10 May 2025 11:40:36 -0300
Message-ID: <af1a02d1-2323-4f6b-ab99-654a0669b557@gmail.com> (raw)
In-Reply-To: <20250510143608.2309616-3-michael@niedermayer.cc>

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On 5/10/2025 11:36 AM, Michael Niedermayer wrote:
> 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: Michael Niedermayer <michael@niedermayer.cc>
> ---
>   libavformat/iamf_parse.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/libavformat/iamf_parse.c b/libavformat/iamf_parse.c
> index abedfdb0668..37fb25962c4 100644
> --- a/libavformat/iamf_parse.c
> +++ b/libavformat/iamf_parse.c
> @@ -304,6 +304,8 @@ static int update_extradata(AVCodecParameters *codecpar)
>           skip_bits(&gb, 4);
>           put_bits(&pb, 4, codecpar->ch_layout.nb_channels); // set channel config
>           ret = put_bits_left(&pb);
> +        if (ret < 0)
> +            return AVERROR_INVALIDDATA;
>           put_bits(&pb, ret, get_bits_long(&gb, ret));
>           flush_put_bits(&pb);

No, there's something wrong because the buffer for PutBytes is fixed and 
local. Maybe 5 bytes was not enough.

Will have a look.

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