uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
                                               uint64_t offset,
                                               int compressed_size)
{
    BDRVQcowState *s = bs->opaque;
    int l2_index, ret;
    uint64_t *l2_table;
    int64_t cluster_offset;
    int nb_csectors;

    ret = get_cluster_table(bs, offset, &l2_table, &l2_index);
    if (ret < 0) {
        return 0;
    }

    /* Compression can't overwrite anything. Fail if the cluster was already
     * allocated. */
    cluster_offset = be64_to_cpu(l2_table[l2_index]);
    if (cluster_offset & L2E_OFFSET_MASK) {
        qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
        return 0;
    }

    cluster_offset = qcow2_alloc_bytes(bs, compressed_size);
    if (cluster_offset < 0) {
        qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
        return 0;
    }

    nb_csectors = ((cluster_offset + compressed_size - 1) >> 9) -
                  (cluster_offset >> 9);

    cluster_offset |= QCOW_OFLAG_COMPRESSED |
                      ((uint64_t)nb_csectors << s->csize_shift);

    /* update L2 table */

    /* compressed clusters never have the copied flag */

    BLKDBG_EVENT(bs->file, BLKDBG_L2_UPDATE_COMPRESSED);
    qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
    l2_table[l2_index] = cpu_to_be64(cluster_offset);
    ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
    if (ret < 0) {
        return 0;
    }

    return cluster_offset;
}

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.