int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index)
{
    BDRVQcowState *s = bs->opaque;
    uint64_t buf[L1_ENTRIES_PER_SECTOR];
    int l1_start_index;
    int i, ret;

    l1_start_index = l1_index & ~(L1_ENTRIES_PER_SECTOR - 1);
    for (i = 0; i < L1_ENTRIES_PER_SECTOR; i++) {
        buf[i] = cpu_to_be64(s->l1_table[l1_start_index + i]);
    }

    ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1,
            s->l1_table_offset + 8 * l1_start_index, sizeof(buf));
    if (ret < 0) {
        return ret;
    }

    BLKDBG_EVENT(bs->file, BLKDBG_L1_UPDATE);
    ret = bdrv_pwrite_sync(bs->file, s->l1_table_offset + 8 * l1_start_index,
        buf, sizeof(buf));
    if (ret < 0) {
        return ret;
    }

    return 0;
}

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.