[FFmpeg-devel] [PATCH] avformat/aviobuf: realloc memory in ffio_ensure_seekback()

[Marton Balint]

On Tue, 15 Sep 2020, Paul B Mahol wrote:

> This removes big CPU overhead for demuxing chained ogg streams.
>
> Signed-off-by: Paul B Mahol <onemda at gmail.com>
> ---
> libavformat/aviobuf.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/libavformat/aviobuf.c b/libavformat/aviobuf.c
> index a77517d712..6d01150f66 100644
> --- a/libavformat/aviobuf.c
> +++ b/libavformat/aviobuf.c
> @@ -1005,12 +1005,11 @@ int ffio_ensure_seekback(AVIOContext *s, int64_t buf_size)
>         return 0;
>     av_assert0(!s->write_flag);
> 
> -    buffer = av_malloc(buf_size);
> +    buffer = s->buffer;
> +    buffer = av_realloc(buffer, buf_size);

It is not guaranteed that buffer is allocated with av_realloc, so you 
cannot realloc it.

Regards,
Marton

>     if (!buffer)
>         return AVERROR(ENOMEM);
> 
> -    memcpy(buffer, s->buffer, filled);
> -    av_free(s->buffer);
>     s->buf_ptr = buffer + (s->buf_ptr - s->buffer);
>     s->buf_end = buffer + (s->buf_end - s->buffer);
>     s->buffer = buffer;
> -- 
> 2.17.1
>
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