int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
{
    BDRVQcowState *s = bs->opaque;
    QCowSnapshot *sn;
    int i, snapshot_index;
    int cur_l1_bytes, sn_l1_bytes;
    int ret;
    uint64_t *sn_l1_table = NULL;

    /* Search the snapshot */
    snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);
    if (snapshot_index < 0) {
        return -ENOENT;
    }
    sn = &s->snapshots[snapshot_index];

    if (sn->disk_size != bs->total_sectors * BDRV_SECTOR_SIZE) {
        error_report("qcow2: Loading snapshots with different disk "
            "size is not implemented");
        ret = -ENOTSUP;
        goto fail;
    }

    /*
     * Make sure that the current L1 table is big enough to contain the whole
     * L1 table of the snapshot. If the snapshot L1 table is smaller, the
     * current one must be padded with zeros.
     */
    ret = qcow2_grow_l1_table(bs, sn->l1_size, true);
    if (ret < 0) {
        goto fail;
    }

    cur_l1_bytes = s->l1_size * sizeof(uint64_t);
    sn_l1_bytes = sn->l1_size * sizeof(uint64_t);

    /*
     * Copy the snapshot L1 table to the current L1 table.
     *
     * Before overwriting the old current L1 table on disk, make sure to
     * increase all refcounts for the clusters referenced by the new one.
     * Decrease the refcount referenced by the old one only when the L1
     * table is overwritten.
     */
    sn_l1_table = g_malloc0(cur_l1_bytes);

    ret = bdrv_pread(bs->file, sn->l1_table_offset, sn_l1_table, sn_l1_bytes);
    if (ret < 0) {
        goto fail;
    }

    ret = qcow2_update_snapshot_refcount(bs, sn->l1_table_offset,
                                         sn->l1_size, 1);
    if (ret < 0) {
        goto fail;
    }

    ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1,
                                        s->l1_table_offset, cur_l1_bytes);
    if (ret < 0) {
        goto fail;
    }

    ret = bdrv_pwrite_sync(bs->file, s->l1_table_offset, sn_l1_table,
                           cur_l1_bytes);
    if (ret < 0) {
        goto fail;
    }

    /*
     * Decrease refcount of clusters of current L1 table.
     *
     * At this point, the in-memory s->l1_table points to the old L1 table,
     * whereas on disk we already have the new one.
     *
     * qcow2_update_snapshot_refcount special cases the current L1 table to use
     * the in-memory data instead of really using the offset to load a new one,
     * which is why this works.
     */
    ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset,
                                         s->l1_size, -1);

    /*
     * Now update the in-memory L1 table to be in sync with the on-disk one. We
     * need to do this even if updating refcounts failed.
     */
    for(i = 0;i < s->l1_size; i++) {
        s->l1_table[i] = be64_to_cpu(sn_l1_table[i]);
    }

    if (ret < 0) {
        goto fail;
    }

    g_free(sn_l1_table);
    sn_l1_table = NULL;

    /*
     * Update QCOW_OFLAG_COPIED in the active L1 table (it may have changed
     * when we decreased the refcount of the old snapshot.
     */
    ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0);
    if (ret < 0) {
        goto fail;
    }

#ifdef DEBUG_ALLOC
    {
        BdrvCheckResult result = {0};
        qcow2_check_refcounts(bs, &result, 0);
    }
#endif
    return 0;

fail:
    g_free(sn_l1_table);
    return ret;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.