[FFmpeg-devel] [PATCH 3/3] avcodec/alsdec: Set channels from data after data is set

[James Almer]

On 3/17/2022 8:30 PM, Michael Niedermayer wrote:
> Fixes: out of array write
> Fixes: 45624/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-6473487382872064
> Fixes: 45626/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-4874997192065024
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>   libavcodec/alsdec.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
> index 822cf211b0..73af829178 100644
> --- a/libavcodec/alsdec.c
> +++ b/libavcodec/alsdec.c
> @@ -1986,7 +1986,7 @@ static av_cold int decode_init(AVCodecContext *avctx)
>       unsigned int c;
>       unsigned int channel_size;
>       int num_buffers, ret;
> -    int channels = avctx->ch_layout.nb_channels;
> +    int channels;
>       ALSDecContext *ctx = avctx->priv_data;
>       ALSSpecificConfig *sconf = &ctx->sconf;
>       ctx->avctx = avctx;
> @@ -2000,6 +2000,7 @@ static av_cold int decode_init(AVCodecContext *avctx)
>           av_log(avctx, AV_LOG_ERROR, "Reading ALSSpecificConfig failed.\n");
>           return ret;
>       }
> +    channels = avctx->ch_layout.nb_channels;
>   
>       if ((ret = check_specific_config(ctx)) < 0) {
>           return ret;

LGTM