[FFmpeg-devel] [PATCH] lavformat/utils: Fix a memleak that st->codec->hw_frames_ctx

[Mark Thompson]

On 20/01/17 02:06, Huang, Zhengxu wrote:
> From 9ceb2ac6a89246f2e686eb3ad3448fbaff5328f7 Mon Sep 17 00:00:00 2001
> From: Zhengxu <zhengxu.maxwell at gmail.com>
> Date: Fri, 13 Jan 2017 10:33:05 +0800
> Subject: [PATCH] lavformat/utils: Fix a memleak that st->codec->hw_frames_ctx
>  is not released.
> 
> Signed-off-by: ChaoX A Liu <chaox.a.liu at gmail.com>
> Signed-off-by: Huang, Zhengxu <zhengxu.maxwell at gmail.com>
> Signed-off-by: Andrew, Zhang <huazh407 at gmail.com>
> ---
>  libavformat/utils.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/libavformat/utils.c b/libavformat/utils.c
> index d5dfca7..cadec15 100644
> --- a/libavformat/utils.c
> +++ b/libavformat/utils.c
> @@ -4127,6 +4127,7 @@ static void free_stream(AVStream **pst)
>  FF_DISABLE_DEPRECATION_WARNINGS
>      av_freep(&st->codec->extradata);
>      av_freep(&st->codec->subtitle_header);
> +    av_buffer_unref(&st->codec->hw_frames_ctx);
>      av_freep(&st->codec);
>  FF_ENABLE_DEPRECATION_WARNINGS
>  #endif
> -- 
> 1.8.3.1
> 

As stated elsewhere, this should never happen in a sane program (AVStream.codec was deprecated before AVCodecContext.hw_frames_ctx was introduced), but I admit that ffmpeg.c cannot be said to be a sane program.

I think the patch is probably ok, but it is very difficult to tell.  Why doesn't the code here already call avcodec_free_context() here to free st->codec properly, including unreffing hw_frames_ctx?  I imagine there is some crazy reason for this (some fields have been copied somewhere else, maybe?), and without knowing that I don't think this patch should be applied.

So, I mostly agree with Hendrik that it is probably better to fix ffmpeg.c to not cause the problem in the first place rather than changing this deprecated code in lavf.

Thanks,

- Mark