Re: [FFmpeg-devel] [PATCH] avdevice/lavfi: Fix double-free on error

From: Timo Rothenpieler <timo@rothenpieler.org>
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH] avdevice/lavfi: Fix double-free on error
Date: Sat, 30 Sep 2023 11:36:14 +0200
Message-ID: <8dd7bc25-7676-4505-a969-41196e7b4d81@rothenpieler.org> (raw)
In-Reply-To: <AS8P250MB07441928C5711C2185E528FE8FC0A@AS8P250MB0744.EURP250.PROD.OUTLOOK.COM>

On 29.09.2023 19:28, Andreas Rheinhardt wrote:
> After the AVFrame has been wrapped into a buffer,
> it is owned by the buffer and must not be freed manually
> any more. Yet this happens on subsequent errors.
> 
> This bug was introduced in 6ca43a9675d651d7ea47c7ba2fafb1bf831c4d0b.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
> ---
>   libavdevice/lavfi.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/libavdevice/lavfi.c b/libavdevice/lavfi.c
> index ec7ebdbc90..2bfd0b81c7 100644
> --- a/libavdevice/lavfi.c
> +++ b/libavdevice/lavfi.c
> @@ -365,7 +365,7 @@ static int lavfi_read_packet(AVFormatContext *avctx, AVPacket *pkt)
>       LavfiContext *lavfi = avctx->priv_data;
>       double min_pts = DBL_MAX;
>       int stream_idx, min_pts_sink_idx = 0;
> -    AVFrame *frame;
> +    AVFrame *frame, *frame_to_free;
>       AVDictionary *frame_metadata;
>       int ret, i;
>       AVStream *st;
> @@ -378,6 +378,7 @@ static int lavfi_read_packet(AVFormatContext *avctx, AVPacket *pkt)
>       frame = av_frame_alloc();
>       if (!frame)
>           return AVERROR(ENOMEM);
> +    frame_to_free = frame;
>   
>       /* iterate through all the graph sinks. Select the sink with the
>        * minimum PTS */
> @@ -423,6 +424,7 @@ static int lavfi_read_packet(AVFormatContext *avctx, AVPacket *pkt)
>               ret = AVERROR(ENOMEM);
>               goto fail;
>           }
> +        frame_to_free = NULL;
>   
>           pkt->data   = pkt->buf->data;
>           pkt->size   = pkt->buf->size;
> @@ -463,12 +465,11 @@ FF_DISABLE_DEPRECATION_WARNINGS
>   FF_ENABLE_DEPRECATION_WARNINGS
>   #endif
>   
> -    if (st->codecpar->codec_type != AVMEDIA_TYPE_VIDEO)
> -        av_frame_free(&frame);
> +    av_frame_free(&frame_to_free);
>   
>       return pkt->size;
>   fail:
> -    av_frame_free(&frame);
> +    av_frame_free(&frame_to_free);
>       return ret;
>   
>   }

Looks sensible to me
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