static int64_t realloc_refcount_block(BlockDriverState *bs, int reftable_index,
                                      uint64_t offset)
{
    BDRVQcowState *s = bs->opaque;
    int64_t new_offset = 0;
    void *refcount_block = NULL;
    int ret;

    /* allocate new refcount block */
    new_offset = qcow2_alloc_clusters(bs, s->cluster_size);
    if (new_offset < 0) {
        fprintf(stderr, "Could not allocate new cluster: %s\n",
                strerror(-new_offset));
        ret = new_offset;
        goto done;
    }

    /* fetch current refcount block content */
    ret = qcow2_cache_get(bs, s->refcount_block_cache, offset, &refcount_block);
    if (ret < 0) {
        fprintf(stderr, "Could not fetch refcount block: %s\n", strerror(-ret));
        goto fail_free_cluster;
    }

    /* new block has not yet been entered into refcount table, therefore it is
     * no refcount block yet (regarding this check) */
    ret = qcow2_pre_write_overlap_check(bs, 0, new_offset, s->cluster_size);
    if (ret < 0) {
        fprintf(stderr, "Could not write refcount block; metadata overlap "
                "check failed: %s\n", strerror(-ret));
        /* the image will be marked corrupt, so don't even attempt on freeing
         * the cluster */
        goto done;
    }

    /* write to new block */
    ret = bdrv_write(bs->file, new_offset / BDRV_SECTOR_SIZE, refcount_block,
            s->cluster_sectors);
    if (ret < 0) {
        fprintf(stderr, "Could not write refcount block: %s\n", strerror(-ret));
        goto fail_free_cluster;
    }

    /* update refcount table */
    assert(!offset_into_cluster(s, new_offset));
    s->refcount_table[reftable_index] = new_offset;
    ret = write_reftable_entry(bs, reftable_index);
    if (ret < 0) {
        fprintf(stderr, "Could not update refcount table: %s\n",
                strerror(-ret));
        goto fail_free_cluster;
    }

    goto done;

fail_free_cluster:
    qcow2_free_clusters(bs, new_offset, s->cluster_size, QCOW2_DISCARD_OTHER);

done:
    if (refcount_block) {
        /* This should never fail, as it would only do so if the given refcount
         * block cannot be found in the cache. As this is impossible as long as
         * there are no bugs, assert the success. */
        int tmp = qcow2_cache_put(bs, s->refcount_block_cache, &refcount_block);
        assert(tmp == 0);
    }

    if (ret < 0) {
        return ret;
    }

    return new_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.