[FFmpeg-devel] [PATCH] avcodec/pthread_frame: fix hw_device_ctx leak

[Andreas Rheinhardt]

Thomas Guillem:
> Reproduced when using the VAAPI va module on VLC 4.0. No leaks when
> setting thread count to 1.
> ---
>  libavcodec/pthread_frame.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/libavcodec/pthread_frame.c b/libavcodec/pthread_frame.c
> index 73b1b7d7d9..4c578aa44a 100644
> --- a/libavcodec/pthread_frame.c
> +++ b/libavcodec/pthread_frame.c
> @@ -747,6 +747,7 @@ void ff_frame_thread_free(AVCodecContext *avctx, int thread_count)
>              av_buffer_unref(&ctx->internal->pool);
>              av_freep(&ctx->internal);
>              av_buffer_unref(&ctx->hw_frames_ctx);
> +            av_buffer_unref(&ctx->hw_device_ctx);
>          }
>  
>          av_frame_free(&p->frame);
> 

The AVCodecContext that is freed here is not a full AVCodecContext: It
never received a reference to hw_device_ctx of its own. Unreferencing
this here will therefore mess up the refcount and lead to use-after-frees.
(What is the reference count of hw_device_ctx at this point? Libavcodec
should only hold one reference at that point, namely the one in the main
(user-facing) AVCodecContext; this reference will be unreferenced when
avcodec_close()/avcodec_free_context() is called for the main context.)

- Andreas