Re: [FFmpeg-devel] [PATCH 2/5] avcodec/smacker: Check input before allocation

From: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH 2/5] avcodec/smacker: Check input before allocation
Date: Thu, 3 Jul 2025 21:14:42 +0200
Message-ID: <AS8P250MB07444270A2BB19C0DC2E05E38F43A@AS8P250MB0744.EURP250.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <20250703020131.2506428-2-michael@niedermayer.cc>

Michael Niedermayer:
> Fixes: Timeout
> Fixes: 421650030/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SMACKAUD_fuzzer-6144441767493632
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavcodec/smacker.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/libavcodec/smacker.c b/libavcodec/smacker.c
> index bd08bc7be28..99009bfd361 100644
> --- a/libavcodec/smacker.c
> +++ b/libavcodec/smacker.c
> @@ -662,6 +662,10 @@ static int smka_decode_frame(AVCodecContext *avctx, AVFrame *frame,
>          } else
>              values[i] = h.entries[0].value;
>      }
> +    if (get_bits_left(&gb) < (stereo+1) * (bits+1) * 8) {
> +        ret = AVERROR_INVALIDDATA;
> +        goto error;
> +    }
>  
>      if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
>          return ret;

What about constant output (which you even optimized in
08e82e5b572b440f4faf160d2eac923ca47a59f8)?

- Andreas

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