Re: [FFmpeg-devel] [PATCH v4 2/3] avformat/sapenc: fix leak in sap_write_header()

[Michael Niedermayer <michael@niedermayer.cc>]

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On Mon, Jun 30, 2025 at 11:01:13PM +0800, Lidong Yan wrote:
> In sap_write_header(), ff_format_set_url() assign new allocated new_url
> to contexts[i]->url but forgot to free it later. Add for loop to free
> contexts[i]->url before av_free(context).
> 
> To prevent from writing free-for-loop in every return point, replace
> `return 0` with `ret = 0` so normal execution can fall through cleanup
> code.
> 
> Signed-off-by: Lidong Yan <502024330056@smail.nju.edu.cn>
> ---
>  libavformat/sapenc.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/libavformat/sapenc.c b/libavformat/sapenc.c
> index 87a834a8d8..0882690ba5 100644
> --- a/libavformat/sapenc.c
> +++ b/libavformat/sapenc.c
> @@ -244,11 +244,15 @@ static int sap_write_header(AVFormatContext *s)
>          goto fail;
>      }
>  
> -    return 0;
> +    ret = 0;
>  


    av_freep(&contexts);
...
    if (sap->ann_size > sap->ann_fd->max_packet_size) {
        av_log(s, AV_LOG_ERROR, "Announcement too large to send in one "
                                "packet\n");
        goto fail;

>  fail:
> +    for (i = 0; i < s->nb_streams; i++)
> +        if (contexts[i])
> +            av_free(contexts[i]->url);


contexts will be NULL so i would assume contexts[i] will segfault

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Rewriting code that is poorly written but fully understood is good.
Rewriting code that one doesnt understand is a sign that one is less smart
than the original author, trying to rewrite it will not make it better.

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