[FFmpeg-devel] [PATCH 2/5] avcodec/allcodecs: Dont play with NULLs

[James Almer]

On 3/21/2022 5:19 PM, Michael Niedermayer wrote:
> Fixes: member access within null pointer of type 'const FFCodec' (aka 'const struct FFCodec')
> Fixes: 45726/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-6554445419249664
> 
> 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/allcodecs.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
> index b1aa7e266b..22d56760ec 100644
> --- a/libavcodec/allcodecs.c
> +++ b/libavcodec/allcodecs.c
> @@ -882,10 +882,11 @@ const AVCodec *av_codec_iterate(void **opaque)
>   
>       ff_thread_once(&av_codec_static_init, av_codec_init_static);
>   
> -    if (c)
> +    if (c) {
>           *opaque = (void*)(i + 1);
> -
> -    return &c->p;
> +        return &c->p;
> +    }
> +    return NULL;

Can't you just do

return (const AVCodec *)c;

Or is that aliasing a problem?

>   }
>   
>   static enum AVCodecID remap_deprecated_codec_id(enum AVCodecID id)