[FFmpeg-devel] [PATCH v3] fftools/opts: Avoid crash when opts could not be allocated

[Andreas Rheinhardt]

Yu Yang:
> If 'opts' could not be allocated, exiting the program to avoid crash when release it. 
> Before setup_find_stream_info_opts(), checking 'orig_nb_streams' is > 0.
> If 'orig_nb_streams' == 0, it doesn't need 'opts' to getting streams info. So directly 
> execute avformat_find_stream_info().
> 
> Reported-by: TOTE Robot <oslab at tsinghua.edu.cn>
> Signed-off-by: Yu Yang <young_chelsea at 163.com>
> ---
>  fftools/cmdutils.c   |  5 ++---
>  fftools/ffmpeg_opt.c | 20 ++++++++++----------
>  2 files changed, 12 insertions(+), 13 deletions(-)
> 
> diff --git a/fftools/cmdutils.c b/fftools/cmdutils.c
> index 3c8e5a82cd..823cc8a632 100644
> --- a/fftools/cmdutils.c
> +++ b/fftools/cmdutils.c
> @@ -2181,13 +2181,12 @@ AVDictionary **setup_find_stream_info_opts(AVFormatContext *s,
>      int i;
>      AVDictionary **opts;
>  
> -    if (!s->nb_streams)
> -        return NULL;
>      opts = av_calloc(s->nb_streams, sizeof(*opts));
>      if (!opts) {
>          av_log(NULL, AV_LOG_ERROR,
>                 "Could not alloc memory for stream options.\n");
> -        return NULL;
> +        avformat_close_input(&s);
> +        exit_program(1);

You went the easy route and exited instead of returning the error; I am
not against this, but notice that you do not need to close s here,
because we are exiting the program anyway; given that this function is
not supposed to receive ownership of s at all, you should not free it.

>      }
>      for (i = 0; i < s->nb_streams; i++)
>          opts[i] = filter_codec_opts(codec_opts, s->streams[i]->codecpar->codec_id,
> diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
> index a703798586..453f3a21dc 100644
> --- a/fftools/ffmpeg_opt.c
> +++ b/fftools/ffmpeg_opt.c
> @@ -1191,17 +1191,17 @@ static int open_input_file(OptionsContext *o, const char *filename)
>          choose_decoder(o, ic, ic->streams[i]);
>  
>      if (find_stream_info) {
> -        AVDictionary **opts = setup_find_stream_info_opts(ic, o->g->codec_opts);
>          int orig_nb_streams = ic->nb_streams;
> -
> -        /* If not enough info to get the stream parameters, we decode the
> -           first frames to get it. (used in mpeg case for example) */
> -        ret = avformat_find_stream_info(ic, opts);
> -
> -        for (i = 0; i < orig_nb_streams; i++)
> -            av_dict_free(&opts[i]);
> -        av_freep(&opts);
> -
> +        if (orig_nb_streams > 0) {
> +            AVDictionary **opts = setup_find_stream_info_opts(ic, o->g->codec_opts);
> +            /* If not enough info to get the stream parameters, we decode the
> +            first frames to get it. (used in mpeg case for example) */
> +            ret = avformat_find_stream_info(ic, opts);
> +            for (i = 0; i < orig_nb_streams; i++)
> +                av_dict_free(&opts[i]);
> +            av_freep(&opts);
> +        } else
> +            ret = avformat_find_stream_info(ic, NULL);

This change makes the code way more uglier than it is.

>          if (ret < 0) {
>              av_log(NULL, AV_LOG_FATAL, "%s: could not find codec parameters\n", filename);
>              if (ic->nb_streams == 0) {
>