avformat/cafdec: Check for EOF in index read loop

Fixes: OOM
Fixes: 27398/clusterfuzz-testcase-minimized-ffmpeg_dem_CAF_fuzzer-541296033975500

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit eb46939e3a)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/cafdec.c

@@ -205,6 +205,8 @@ static int read_pakt_chunk(AVFormatContext *s, int64_t size)
 
     st->duration = 0;
     for (i = 0; i < num_packets; i++) {
+        if (avio_feof(pb))
+            return AVERROR_INVALIDDATA;
         av_add_index_entry(s->streams[0], pos, st->duration, 0, 0, AVINDEX_KEYFRAME);
         pos += caf->bytes_per_packet ? caf->bytes_per_packet : ff_mp4_read_descr_len(pb);
         st->duration += caf->frames_per_packet ? caf->frames_per_packet : ff_mp4_read_descr_len(pb);