[FFmpeg-devel] [PATCH 3/4] avformat/dvdvideodec: Only free allocated buffers

[Marth64]

Nevermind, disregard. They do not, and I misread. Thanks for catching this.

On Sat, Mar 2, 2024 at 8:31 PM Marth64 <marth64 at proxyid.net> wrote:

> FYI: hls, dashdec do the same av_freep(). Doesn't make this right, but
> saying that was where I used as an example (so they should probably fixed
> too?)
>
> On Sat, Mar 2, 2024 at 10:17 AM Andreas Rheinhardt <
> andreas.rheinhardt at outlook.com> wrote:
>
>> James Almer:
>> > On 3/2/2024 12:47 PM, Andreas Rheinhardt wrote:
>> >> Andreas Rheinhardt:
>> >>> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
>> >>> ---
>> >>> How has this slipped through?
>> >>
>> >> Answer: AVIOContext starts with an AVClass* that is unset when using
>> >> ffio_init_context(). Therefore the av_freep() leads to freeing of a
>> NULL
>> >> pointer which does not segfault.
>> >
>> > Would setting s->av_class to &ff_avio_options in ffio_init_context()
>> > prevent this from happening again?
>> >
>>
>> ff_avio_options is not an AVClass, so this is wrong; setting it to
>> ff_avio_class would also be wrong, because said class is only to be used
>> with the URLProtocol-based AVIOContexts (the child_next and
>> child_class_iterate callbacks are designed for this; the former returns
>> the AVIOContext's opaque, believing it to point to an URLContext, yet in
>> general it need not point to an AVClass-enabled struct at all).
>>
>> In fact, ff_avio_options etc. should be moved to avio.c. I'll look into
>> this.
>>
>> >>
>> >>> Btw: This patchset is based upon code inspection, not on reading
>> >>> actual files.
>> >>>
>> >>>   libavformat/dvdvideodec.c | 1 -
>> >>>   1 file changed, 1 deletion(-)
>> >>>
>> >>> diff --git a/libavformat/dvdvideodec.c b/libavformat/dvdvideodec.c
>> >>> index ef2d4e6df4..f2f23affb2 100644
>> >>> --- a/libavformat/dvdvideodec.c
>> >>> +++ b/libavformat/dvdvideodec.c
>> >>> @@ -1202,7 +1202,6 @@ static void
>> >>> dvdvideo_subdemux_close(AVFormatContext *s)
>> >>>       DVDVideoDemuxContext *c = s->priv_data;
>> >>>         av_freep(&c->mpeg_pb.pub.buffer);
>> >>> -    av_freep(&c->mpeg_pb);
>> >>>       avformat_close_input(&c->mpeg_ctx);
>> >>>   }
>> >>>
>> >>
>>
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>