Code: long Segment::ParseNext(
    const Cluster* pCurr,
    const Cluster*& pResult,
    long long& pos,
    long& len)
{
    assert(pCurr);
    assert(!pCurr->EOS());
    assert(m_clusters);
 
    pResult = 0;
 
    if (pCurr->m_index >= 0)  //loaded (not merely preloaded)
    {
        assert(m_clusters[pCurr->m_index] == pCurr);
 
        const long next_idx = pCurr->m_index + 1;
 
        if (next_idx < m_clusterCount)
        {
            pResult = m_clusters[next_idx];
            return 0;  //success
        }
 
 
        const long result = LoadCluster(pos, len);
 
        if (result < 0)  //error or underflow
            return result;
 
        if (result > 0)  //no more clusters
        {
            return 1;
        }
 
        pResult = GetLast();
        return 0;  //success
     }
 
    assert(m_pos > 0);
 
    long long total, avail;
 
    long status = m_pReader->Length(&total, &avail);
 
    if (status < 0)  //error
        return status;
 
    assert((total < 0) || (avail <= total));
 
    const long long segment_stop = (m_size < 0) ? -1 : m_start + m_size;
 
 
    pos = pCurr->m_element_start;
 
    if (pCurr->m_element_size >= 0)
        pos += pCurr->m_element_size;
     else
    {
        if ((pos + 1) > avail)
        {
            len = 1;
            return E_BUFFER_NOT_FULL;
        }
 
        long long result = GetUIntLength(m_pReader, pos, len);
 
        if (result < 0)  //error
            return static_cast<long>(result);
 
        if (result > 0)  //weird
            return E_BUFFER_NOT_FULL;
 
        if ((segment_stop >= 0) && ((pos + len) > segment_stop))
            return E_FILE_FORMAT_INVALID;
 
        if ((pos + len) > avail)
            return E_BUFFER_NOT_FULL;
        const long long id = ReadUInt(m_pReader, pos, len);
        if (id != 0x0F43B675)  //weird: not Cluster ID
            return -1;
        pos += len;  //consume ID
        if ((pos + 1) > avail)
        {
            len = 1;
            return E_BUFFER_NOT_FULL;
        }
        result = GetUIntLength(m_pReader, pos, len);
        if (result < 0)  //error
            return static_cast<long>(result);
        if (result > 0)  //weird
            return E_BUFFER_NOT_FULL;
        if ((segment_stop >= 0) && ((pos + len) > segment_stop))
            return E_FILE_FORMAT_INVALID;
        if ((pos + len) > avail)
            return E_BUFFER_NOT_FULL;
        const long long size = ReadUInt(m_pReader, pos, len);
        if (size < 0) //error
            return static_cast<long>(size);
        pos += len;  //consume size field
        const long long unknown_size = (1LL << (7 * len)) - 1;
        if (size == unknown_size)          //TODO: should never happen
            return E_FILE_FORMAT_INVALID;  //TODO: resolve this
        if ((segment_stop >= 0) && ((pos + size) > segment_stop))
            return E_FILE_FORMAT_INVALID;
        pos += size;  //consume payload (that is, the current cluster)
        assert((segment_stop < 0) || (pos <= segment_stop));
    }
    for (;;)
    {
        const long status = DoParseNext(pResult, pos, len);
        if (status <= 1)
            return status;
    }
 }

Vulnerability Type: DoS Exec Code Overflow Mem. Corr. 
CWE ID: CWE-119
Summary: libvpx in mediaserver in Android 4.x before 4.4.4, 5.x before 5.1.1 LMY49H, and 6.0 before 2016-03-01 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted media file, related to libwebm/mkvparser.cpp and other files, aka internal bug 23452792.
Commit Message: libwebm: Pull from upstream

Rolling mkvparser from upstream. Primarily for fixing a bug on parsing
failures with certain Opus WebM files.

Upstream commit hash of this pull: 574045edd4ecbeb802ee3f1d214b5510269852ae

The diff is so huge because there were some style clean ups upstream.
But it was ensured that there were no breaking changes when the style
clean ups was done upstream.

Change-Id: Ib6e907175484b4b0ae1b55ab39522ea3188ad039