Re: [FFmpeg-devel] [PATCH 4/6] avformat/demux_utils: Avoid leaking the packet in ff_add_attached_pic()

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Michael Niedermayer:
> Fixes: memleak
> Fixes: 67714/clusterfuzz-testcase-minimized-ffmpeg_dem_MOV_fuzzer-5671570999476224
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavformat/demux_utils.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavformat/demux_utils.c b/libavformat/demux_utils.c
> index 86f551245be..96e6e20d1ec 100644
> --- a/libavformat/demux_utils.c
> +++ b/libavformat/demux_utils.c
> @@ -123,9 +123,9 @@ int ff_add_attached_pic(AVFormatContext *s, AVStream *st0, AVIOContext *pb,
>      if (!st && !(st = avformat_new_stream(s, NULL)))
>          return AVERROR(ENOMEM);
>      pkt = &st->attached_pic;
> +    av_packet_unref(pkt);
>      if (buf) {
>          av_assert1(*buf);
> -        av_packet_unref(pkt);
>          pkt->buf  = *buf;
>          pkt->data = (*buf)->data;
>          pkt->size = (*buf)->size - AV_INPUT_BUFFER_PADDING_SIZE;

This seems to be from the ff_add_attached_pic() call in
mov_read_chapters() with the referenced stream having been created in
mov_read_covr(). The latter does not set a proper id -- it just takes
what avformat_new_stream() sets as id on every new stream (namely zero).
So it makes no real sense to compare it to the ids contained in
chapter_tracks (can really every track be reinterpreted as chapter
track?). But I am no mov/mp4 expert.
Anyway, does the following fix it?

diff --git a/libavformat/mov.c b/libavformat/mov.c
index 7bdeeb99f9..51d97296f1 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -8820,7 +8820,7 @@ static void mov_read_chapters(AVFormatContext *s)

         if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
             st->disposition |= AV_DISPOSITION_ATTACHED_PIC |
AV_DISPOSITION_TIMED_THUMBNAILS;
-            if (sti->nb_index_entries) {
+            if (!st->attached_pic.data && sti->nb_index_entries) {
                 // Retrieve the first frame, if possible
                 AVIndexEntry *sample = &sti->index_entries[0];
                 if (avio_seek(sc->pb, sample->pos, SEEK_SET) !=
sample->pos) {
s

- Andreas

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