avformat/mxfdec: Fix DoS issues in mxf_read_index_entry_array()

Fixes: 20170829A.mxf

Co-Author: 张洪亮(望初)" <wangchu.zhl@alibaba-inc.com>
Found-by: Xiaohei and Wangchu from Alibaba Security Team
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
static int mxf_read_source_clip(void *arg, AVIOContext *pb, int tag, int size, UID uid, int64_t klv_offset)
{
    MXFStructuralComponent *source_clip = arg;
    switch(tag) {
    case 0x0202:
        source_clip->duration = avio_rb64(pb);
        break;
    case 0x1201:
        source_clip->start_position = avio_rb64(pb);
        break;
    case 0x1101:
        /* UMID, only get last 16 bytes */
        avio_read(pb, source_clip->source_package_ul, 16);
        avio_read(pb, source_clip->source_package_uid, 16);
        break;
    case 0x1102:
        source_clip->source_track_id = avio_rb32(pb);
        break;
    }
    return 0;
}

static int mxf_read_source_clip(void *arg, AVIOContext *pb, int tag, int size, UID uid, int64_t klv_offset)
{
    MXFStructuralComponent *source_clip = arg;
    switch(tag) {
    case 0x0202:
        source_clip->duration = avio_rb64(pb);
        break;
    case 0x1201:
        source_clip->start_position = avio_rb64(pb);
        break;
    case 0x1101:
        /* UMID, only get last 16 bytes */
        avio_read(pb, source_clip->source_package_ul, 16);
        avio_read(pb, source_clip->source_package_uid, 16);
        break;
    case 0x1102:
        source_clip->source_track_id = avio_rb32(pb);
        break;
    }
    return 0;
}
