cri: implement RuntimeConfig rpc
The rpc only reports one field, i.e. the cgroup driver, to kubelet. Containerd determines the effective cgroup driver by looking at all runtime handlers, starting from the default runtime handler (the rest in alphabetical order), and returning the cgroup driver setting of the first runtime handler that supports one. If no runtime handler supports cgroup driver (i.e. has a config option for it) containerd falls back to auto-detection, returning systemd if systemd is running and cgroupfs otherwise. This patch implements the CRI server side of Kubernetes KEP-4033: https://github.com/kubernetes/enhancements/tree/master/keps/sig-node/4033-group-driver-detection-over-cri Signed-off-by: Markus Lehtonen <markus.lehtonen@intel.com>
This commit is contained in:
Markus Lehtonen
386
vendor/github.com/opencontainers/runc/libcontainer/cgroups/devices/devices_emulator.go
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386
vendor/github.com/opencontainers/runc/libcontainer/cgroups/devices/devices_emulator.go
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// SPDX-License-Identifier: Apache-2.0
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/*
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* Copyright (C) 2020 Aleksa Sarai <cyphar@cyphar.com>
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* Copyright (C) 2020 SUSE LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package devices
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import (
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"bufio"
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"fmt"
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"io"
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"sort"
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"strconv"
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"strings"
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"github.com/opencontainers/runc/libcontainer/devices"
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)
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// deviceMeta is a Rule without the Allow or Permissions fields, and no
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// wildcard-type support. It's effectively the "match" portion of a metadata
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// rule, for the purposes of our emulation.
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type deviceMeta struct {
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node devices.Type
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major int64
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minor int64
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}
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// deviceRule is effectively the tuple (deviceMeta, Permissions).
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type deviceRule struct {
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meta deviceMeta
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perms devices.Permissions
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}
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// deviceRules is a mapping of device metadata rules to the associated
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// permissions in the ruleset.
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type deviceRules map[deviceMeta]devices.Permissions
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func (r deviceRules) orderedEntries() []deviceRule {
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var rules []deviceRule
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for meta, perms := range r {
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rules = append(rules, deviceRule{meta: meta, perms: perms})
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}
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sort.Slice(rules, func(i, j int) bool {
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// Sort by (major, minor, type).
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a, b := rules[i].meta, rules[j].meta
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return a.major < b.major ||
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(a.major == b.major && a.minor < b.minor) ||
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(a.major == b.major && a.minor == b.minor && a.node < b.node)
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})
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return rules
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}
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type Emulator struct {
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defaultAllow bool
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rules deviceRules
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}
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func (e *Emulator) IsBlacklist() bool {
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return e.defaultAllow
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}
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func (e *Emulator) IsAllowAll() bool {
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return e.IsBlacklist() && len(e.rules) == 0
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}
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func parseLine(line string) (*deviceRule, error) {
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// Input: node major:minor perms.
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fields := strings.FieldsFunc(line, func(r rune) bool {
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return r == ' ' || r == ':'
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})
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if len(fields) != 4 {
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return nil, fmt.Errorf("malformed devices.list rule %s", line)
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}
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var (
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rule deviceRule
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node = fields[0]
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major = fields[1]
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minor = fields[2]
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perms = fields[3]
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)
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// Parse the node type.
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switch node {
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case "a":
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// Super-special case -- "a" always means every device with every
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// access mode. In fact, for devices.list this actually indicates that
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// the cgroup is in black-list mode.
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// TODO: Double-check that the entire file is "a *:* rwm".
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return nil, nil
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case "b":
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rule.meta.node = devices.BlockDevice
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case "c":
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rule.meta.node = devices.CharDevice
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default:
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return nil, fmt.Errorf("unknown device type %q", node)
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}
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// Parse the major number.
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if major == "*" {
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rule.meta.major = devices.Wildcard
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} else {
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val, err := strconv.ParseUint(major, 10, 32)
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if err != nil {
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return nil, fmt.Errorf("invalid major number: %w", err)
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}
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rule.meta.major = int64(val)
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}
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// Parse the minor number.
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if minor == "*" {
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rule.meta.minor = devices.Wildcard
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} else {
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val, err := strconv.ParseUint(minor, 10, 32)
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if err != nil {
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return nil, fmt.Errorf("invalid minor number: %w", err)
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}
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rule.meta.minor = int64(val)
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}
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// Parse the access permissions.
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rule.perms = devices.Permissions(perms)
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if !rule.perms.IsValid() || rule.perms.IsEmpty() {
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return nil, fmt.Errorf("parse access mode: contained unknown modes or is empty: %q", perms)
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}
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return &rule, nil
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}
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func (e *Emulator) addRule(rule deviceRule) error { //nolint:unparam
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if e.rules == nil {
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e.rules = make(map[deviceMeta]devices.Permissions)
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}
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// Merge with any pre-existing permissions.
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oldPerms := e.rules[rule.meta]
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newPerms := rule.perms.Union(oldPerms)
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e.rules[rule.meta] = newPerms
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return nil
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}
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func (e *Emulator) rmRule(rule deviceRule) error {
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// Give an error if any of the permissions requested to be removed are
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// present in a partially-matching wildcard rule, because such rules will
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// be ignored by cgroupv1.
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//
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// This is a diversion from cgroupv1, but is necessary to avoid leading
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// users into a false sense of security. cgroupv1 will silently(!) ignore
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// requests to remove partial exceptions, but we really shouldn't do that.
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//
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// It may seem like we could just "split" wildcard rules which hit this
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// issue, but unfortunately there are 2^32 possible major and minor
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// numbers, which would exhaust kernel memory quickly if we did this. Not
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// to mention it'd be really slow (the kernel side is implemented as a
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// linked-list of exceptions).
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for _, partialMeta := range []deviceMeta{
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{node: rule.meta.node, major: devices.Wildcard, minor: rule.meta.minor},
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{node: rule.meta.node, major: rule.meta.major, minor: devices.Wildcard},
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{node: rule.meta.node, major: devices.Wildcard, minor: devices.Wildcard},
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} {
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// This wildcard rule is equivalent to the requested rule, so skip it.
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if rule.meta == partialMeta {
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continue
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}
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// Only give an error if the set of permissions overlap.
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partialPerms := e.rules[partialMeta]
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if !partialPerms.Intersection(rule.perms).IsEmpty() {
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return fmt.Errorf("requested rule [%v %v] not supported by devices cgroupv1 (cannot punch hole in existing wildcard rule [%v %v])", rule.meta, rule.perms, partialMeta, partialPerms)
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}
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}
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// Subtract all of the permissions listed from the full match rule. If the
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// rule didn't exist, all of this is a no-op.
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newPerms := e.rules[rule.meta].Difference(rule.perms)
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if newPerms.IsEmpty() {
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delete(e.rules, rule.meta)
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} else {
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e.rules[rule.meta] = newPerms
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}
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// TODO: The actual cgroup code doesn't care if an exception didn't exist
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// during removal, so not erroring out here is /accurate/ but quite
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// worrying. Maybe we should do additional validation, but again we
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// have to worry about backwards-compatibility.
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return nil
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}
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func (e *Emulator) allow(rule *deviceRule) error {
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// This cgroup is configured as a black-list. Reset the entire emulator,
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// and put is into black-list mode.
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if rule == nil || rule.meta.node == devices.WildcardDevice {
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*e = Emulator{
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defaultAllow: true,
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rules: nil,
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}
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return nil
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}
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var err error
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if e.defaultAllow {
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err = wrapErr(e.rmRule(*rule), "unable to remove 'deny' exception")
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} else {
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err = wrapErr(e.addRule(*rule), "unable to add 'allow' exception")
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}
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return err
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}
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func (e *Emulator) deny(rule *deviceRule) error {
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// This cgroup is configured as a white-list. Reset the entire emulator,
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// and put is into white-list mode.
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if rule == nil || rule.meta.node == devices.WildcardDevice {
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*e = Emulator{
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defaultAllow: false,
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rules: nil,
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}
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return nil
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}
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var err error
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if e.defaultAllow {
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err = wrapErr(e.addRule(*rule), "unable to add 'deny' exception")
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} else {
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err = wrapErr(e.rmRule(*rule), "unable to remove 'allow' exception")
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}
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return err
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}
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func (e *Emulator) Apply(rule devices.Rule) error {
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if !rule.Type.CanCgroup() {
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return fmt.Errorf("cannot add rule [%#v] with non-cgroup type %q", rule, rule.Type)
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}
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innerRule := &deviceRule{
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meta: deviceMeta{
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node: rule.Type,
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major: rule.Major,
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minor: rule.Minor,
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},
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perms: rule.Permissions,
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}
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if innerRule.meta.node == devices.WildcardDevice {
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innerRule = nil
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}
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if rule.Allow {
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return e.allow(innerRule)
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}
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return e.deny(innerRule)
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}
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// EmulatorFromList takes a reader to a "devices.list"-like source, and returns
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// a new Emulator that represents the state of the devices cgroup. Note that
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// black-list devices cgroups cannot be fully reconstructed, due to limitations
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// in the devices cgroup API. Instead, such cgroups are always treated as
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// "allow all" cgroups.
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func EmulatorFromList(list io.Reader) (*Emulator, error) {
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// Normally cgroups are in black-list mode by default, but the way we
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// figure out the current mode is whether or not devices.list has an
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// allow-all rule. So we default to a white-list, and the existence of an
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// "a *:* rwm" entry will tell us otherwise.
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e := &Emulator{
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defaultAllow: false,
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}
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// Parse the "devices.list".
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s := bufio.NewScanner(list)
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for s.Scan() {
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line := s.Text()
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deviceRule, err := parseLine(line)
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if err != nil {
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return nil, fmt.Errorf("error parsing line %q: %w", line, err)
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}
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// "devices.list" is an allow list. Note that this means that in
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// black-list mode, we have no idea what rules are in play. As a
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// result, we need to be very careful in Transition().
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if err := e.allow(deviceRule); err != nil {
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return nil, fmt.Errorf("error adding devices.list rule: %w", err)
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}
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}
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if err := s.Err(); err != nil {
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return nil, fmt.Errorf("error reading devices.list lines: %w", err)
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}
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return e, nil
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}
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// Transition calculates what is the minimally-disruptive set of rules need to
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// be applied to a devices cgroup in order to transition to the given target.
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// This means that any already-existing rules will not be applied, and
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// disruptive rules (like denying all device access) will only be applied if
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// necessary.
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//
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// This function is the sole reason for all of Emulator -- to allow us
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// to figure out how to update a containers' cgroups without causing spurious
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// device errors (if possible).
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func (source *Emulator) Transition(target *Emulator) ([]*devices.Rule, error) {
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var transitionRules []*devices.Rule
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oldRules := source.rules
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// If the default policy doesn't match, we need to include a "disruptive"
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// rule (either allow-all or deny-all) in order to switch the cgroup to the
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// correct default policy.
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//
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// However, due to a limitation in "devices.list" we cannot be sure what
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// deny rules are in place in a black-list cgroup. Thus if the source is a
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// black-list we also have to include a disruptive rule.
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if source.IsBlacklist() || source.defaultAllow != target.defaultAllow {
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transitionRules = append(transitionRules, &devices.Rule{
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Type: 'a',
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Major: -1,
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Minor: -1,
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Permissions: devices.Permissions("rwm"),
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Allow: target.defaultAllow,
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})
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// The old rules are only relevant if we aren't starting out with a
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// disruptive rule.
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oldRules = nil
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}
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// NOTE: We traverse through the rules in a sorted order so we always write
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// the same set of rules (this is to aid testing).
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// First, we create inverse rules for any old rules not in the new set.
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// This includes partial-inverse rules for specific permissions. This is a
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// no-op if we added a disruptive rule, since oldRules will be empty.
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for _, rule := range oldRules.orderedEntries() {
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meta, oldPerms := rule.meta, rule.perms
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newPerms := target.rules[meta]
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droppedPerms := oldPerms.Difference(newPerms)
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if !droppedPerms.IsEmpty() {
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transitionRules = append(transitionRules, &devices.Rule{
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Type: meta.node,
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Major: meta.major,
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Minor: meta.minor,
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Permissions: droppedPerms,
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Allow: target.defaultAllow,
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})
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}
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}
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// Add any additional rules which weren't in the old set. We happen to
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// filter out rules which are present in both sets, though this isn't
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// strictly necessary.
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for _, rule := range target.rules.orderedEntries() {
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meta, newPerms := rule.meta, rule.perms
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oldPerms := oldRules[meta]
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gainedPerms := newPerms.Difference(oldPerms)
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if !gainedPerms.IsEmpty() {
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transitionRules = append(transitionRules, &devices.Rule{
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Type: meta.node,
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Major: meta.major,
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Minor: meta.minor,
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Permissions: gainedPerms,
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Allow: !target.defaultAllow,
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})
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}
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}
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return transitionRules, nil
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}
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// Rules returns the minimum set of rules necessary to convert a *deny-all*
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// cgroup to the emulated filter state (note that this is not the same as a
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// default cgroupv1 cgroup -- which is allow-all). This is effectively just a
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// wrapper around Transition() with the source emulator being an empty cgroup.
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func (e *Emulator) Rules() ([]*devices.Rule, error) {
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defaultCgroup := &Emulator{defaultAllow: false}
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return defaultCgroup.Transition(e)
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}
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func wrapErr(err error, text string) error {
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if err == nil {
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return nil
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}
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return fmt.Errorf(text+": %w", err)
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}
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Reference in New Issue
Block a user