static int perform_cow(BlockDriverState *bs, QCowL2Meta *m, Qcow2COWRegion *r)
{
    BDRVQcowState *s = bs->opaque;
    int ret;

    if (r->nb_sectors == 0) {
        return 0;
    }

    qemu_co_mutex_unlock(&s->lock);
    ret = copy_sectors(bs, m->offset / BDRV_SECTOR_SIZE, m->alloc_offset,
                       r->offset / BDRV_SECTOR_SIZE,
                       r->offset / BDRV_SECTOR_SIZE + r->nb_sectors);
    qemu_co_mutex_lock(&s->lock);

    if (ret < 0) {
        return ret;
    }

    /*
     * Before we update the L2 table to actually point to the new cluster, we
     * need to be sure that the refcounts have been increased and COW was
     * handled.
     */
    qcow2_cache_depends_on_flush(s->l2_table_cache);

    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.