422 lines
10 KiB
Go
422 lines
10 KiB
Go
// +build linux
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package fs
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import (
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"bufio"
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"fmt"
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"os"
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"path/filepath"
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"strings"
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"sync"
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"github.com/opencontainers/runc/libcontainer/cgroups"
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"github.com/opencontainers/runc/libcontainer/configs"
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libcontainerUtils "github.com/opencontainers/runc/libcontainer/utils"
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"github.com/pkg/errors"
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"golang.org/x/sys/unix"
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)
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var (
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subsystemsLegacy = subsystemSet{
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&CpusetGroup{},
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&DevicesGroup{},
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&MemoryGroup{},
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&CpuGroup{},
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&CpuacctGroup{},
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&PidsGroup{},
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&BlkioGroup{},
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&HugetlbGroup{},
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&NetClsGroup{},
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&NetPrioGroup{},
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&PerfEventGroup{},
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&FreezerGroup{},
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&NameGroup{GroupName: "name=systemd", Join: true},
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}
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HugePageSizes, _ = cgroups.GetHugePageSize()
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)
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var errSubsystemDoesNotExist = errors.New("cgroup: subsystem does not exist")
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type subsystemSet []subsystem
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func (s subsystemSet) Get(name string) (subsystem, error) {
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for _, ss := range s {
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if ss.Name() == name {
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return ss, nil
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}
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}
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return nil, errSubsystemDoesNotExist
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}
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type subsystem interface {
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// Name returns the name of the subsystem.
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Name() string
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// Returns the stats, as 'stats', corresponding to the cgroup under 'path'.
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GetStats(path string, stats *cgroups.Stats) error
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// Creates and joins the cgroup represented by 'cgroupData'.
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Apply(*cgroupData) error
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// Set the cgroup represented by cgroup.
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Set(path string, cgroup *configs.Cgroup) error
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}
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type manager struct {
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mu sync.Mutex
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cgroups *configs.Cgroup
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rootless bool // ignore permission-related errors
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paths map[string]string
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}
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func NewManager(cg *configs.Cgroup, paths map[string]string, rootless bool) cgroups.Manager {
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return &manager{
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cgroups: cg,
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paths: paths,
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rootless: rootless,
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}
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}
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// The absolute path to the root of the cgroup hierarchies.
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var cgroupRootLock sync.Mutex
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var cgroupRoot string
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// Gets the cgroupRoot.
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func getCgroupRoot() (string, error) {
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cgroupRootLock.Lock()
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defer cgroupRootLock.Unlock()
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if cgroupRoot != "" {
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return cgroupRoot, nil
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}
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f, err := os.Open("/proc/self/mountinfo")
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if err != nil {
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return "", err
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}
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defer f.Close()
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var root string
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scanner := bufio.NewScanner(f)
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for scanner.Scan() {
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text := scanner.Text()
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fields := strings.Split(text, " ")
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// Safe as mountinfo encodes mountpoints with spaces as \040.
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index := strings.Index(text, " - ")
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postSeparatorFields := strings.Fields(text[index+3:])
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numPostFields := len(postSeparatorFields)
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// This is an error as we can't detect if the mount is for "cgroup"
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if numPostFields == 0 {
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return "", fmt.Errorf("mountinfo: found no fields post '-' in %q", text)
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}
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if postSeparatorFields[0] == "cgroup" {
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// Check that the mount is properly formatted.
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if numPostFields < 3 {
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return "", fmt.Errorf("Error found less than 3 fields post '-' in %q", text)
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}
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root = filepath.Dir(fields[4])
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break
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}
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}
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if err := scanner.Err(); err != nil {
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return "", err
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}
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if root == "" {
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return "", errors.New("no cgroup mount found in mountinfo")
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}
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if _, err := os.Stat(root); err != nil {
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return "", err
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}
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cgroupRoot = root
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return cgroupRoot, nil
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}
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type cgroupData struct {
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root string
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innerPath string
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config *configs.Cgroup
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pid int
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}
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// isIgnorableError returns whether err is a permission error (in the loose
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// sense of the word). This includes EROFS (which for an unprivileged user is
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// basically a permission error) and EACCES (for similar reasons) as well as
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// the normal EPERM.
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func isIgnorableError(rootless bool, err error) bool {
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// We do not ignore errors if we are root.
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if !rootless {
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return false
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}
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// TODO: rm errors.Cause once we switch to %w everywhere
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err = errors.Cause(err)
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// Is it an ordinary EPERM?
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if errors.Is(err, os.ErrPermission) {
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return true
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}
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// Handle some specific syscall errors.
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var errno unix.Errno
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if errors.As(err, &errno) {
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return errno == unix.EROFS || errno == unix.EPERM || errno == unix.EACCES
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}
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return false
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}
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func (m *manager) getSubsystems() subsystemSet {
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return subsystemsLegacy
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}
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func (m *manager) Apply(pid int) (err error) {
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if m.cgroups == nil {
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return nil
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}
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m.mu.Lock()
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defer m.mu.Unlock()
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var c = m.cgroups
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d, err := getCgroupData(m.cgroups, pid)
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if err != nil {
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return err
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}
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m.paths = make(map[string]string)
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if c.Paths != nil {
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for name, path := range c.Paths {
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_, err := d.path(name)
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if err != nil {
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if cgroups.IsNotFound(err) {
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continue
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}
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return err
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}
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m.paths[name] = path
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}
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return cgroups.EnterPid(m.paths, pid)
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}
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for _, sys := range m.getSubsystems() {
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p, err := d.path(sys.Name())
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if err != nil {
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// The non-presence of the devices subsystem is
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// considered fatal for security reasons.
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if cgroups.IsNotFound(err) && (c.SkipDevices || sys.Name() != "devices") {
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continue
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}
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return err
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}
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m.paths[sys.Name()] = p
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if err := sys.Apply(d); err != nil {
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// In the case of rootless (including euid=0 in userns), where an
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// explicit cgroup path hasn't been set, we don't bail on error in
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// case of permission problems. Cases where limits have been set
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// (and we couldn't create our own cgroup) are handled by Set.
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if isIgnorableError(m.rootless, err) && m.cgroups.Path == "" {
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delete(m.paths, sys.Name())
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continue
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}
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return err
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}
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}
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return nil
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}
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func (m *manager) Destroy() error {
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if m.cgroups == nil || m.cgroups.Paths != nil {
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return nil
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}
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m.mu.Lock()
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defer m.mu.Unlock()
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if err := cgroups.RemovePaths(m.paths); err != nil {
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return err
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}
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m.paths = make(map[string]string)
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return nil
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}
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func (m *manager) Path(subsys string) string {
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m.mu.Lock()
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defer m.mu.Unlock()
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return m.paths[subsys]
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}
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func (m *manager) GetStats() (*cgroups.Stats, error) {
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m.mu.Lock()
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defer m.mu.Unlock()
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stats := cgroups.NewStats()
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for name, path := range m.paths {
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sys, err := m.getSubsystems().Get(name)
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if err == errSubsystemDoesNotExist || !cgroups.PathExists(path) {
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continue
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}
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if err := sys.GetStats(path, stats); err != nil {
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return nil, err
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}
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}
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return stats, nil
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}
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func (m *manager) Set(container *configs.Config) error {
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if container.Cgroups == nil {
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return nil
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}
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// If Paths are set, then we are just joining cgroups paths
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// and there is no need to set any values.
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if m.cgroups != nil && m.cgroups.Paths != nil {
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return nil
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}
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m.mu.Lock()
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defer m.mu.Unlock()
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for _, sys := range m.getSubsystems() {
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path := m.paths[sys.Name()]
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if err := sys.Set(path, container.Cgroups); err != nil {
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if m.rootless && sys.Name() == "devices" {
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continue
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}
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// When m.Rootless is true, errors from the device subsystem are ignored because it is really not expected to work.
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// However, errors from other subsystems are not ignored.
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// see @test "runc create (rootless + limits + no cgrouppath + no permission) fails with informative error"
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if path == "" {
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// We never created a path for this cgroup, so we cannot set
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// limits for it (though we have already tried at this point).
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return fmt.Errorf("cannot set %s limit: container could not join or create cgroup", sys.Name())
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}
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return err
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}
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}
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return nil
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}
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// Freeze toggles the container's freezer cgroup depending on the state
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// provided
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func (m *manager) Freeze(state configs.FreezerState) error {
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path := m.Path("freezer")
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if m.cgroups == nil || path == "" {
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return errors.New("cannot toggle freezer: cgroups not configured for container")
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}
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prevState := m.cgroups.Resources.Freezer
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m.cgroups.Resources.Freezer = state
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freezer := &FreezerGroup{}
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if err := freezer.Set(path, m.cgroups); err != nil {
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m.cgroups.Resources.Freezer = prevState
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return err
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}
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return nil
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}
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func (m *manager) GetPids() ([]int, error) {
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return cgroups.GetPids(m.Path("devices"))
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}
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func (m *manager) GetAllPids() ([]int, error) {
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return cgroups.GetAllPids(m.Path("devices"))
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}
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func getCgroupData(c *configs.Cgroup, pid int) (*cgroupData, error) {
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root, err := getCgroupRoot()
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if err != nil {
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return nil, err
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}
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if (c.Name != "" || c.Parent != "") && c.Path != "" {
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return nil, errors.New("cgroup: either Path or Name and Parent should be used")
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}
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// XXX: Do not remove this code. Path safety is important! -- cyphar
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cgPath := libcontainerUtils.CleanPath(c.Path)
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cgParent := libcontainerUtils.CleanPath(c.Parent)
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cgName := libcontainerUtils.CleanPath(c.Name)
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innerPath := cgPath
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if innerPath == "" {
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innerPath = filepath.Join(cgParent, cgName)
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}
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return &cgroupData{
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root: root,
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innerPath: innerPath,
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config: c,
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pid: pid,
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}, nil
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}
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func (raw *cgroupData) path(subsystem string) (string, error) {
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mnt, err := cgroups.FindCgroupMountpoint(raw.root, subsystem)
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// If we didn't mount the subsystem, there is no point we make the path.
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if err != nil {
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return "", err
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}
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// If the cgroup name/path is absolute do not look relative to the cgroup of the init process.
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if filepath.IsAbs(raw.innerPath) {
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// Sometimes subsystems can be mounted together as 'cpu,cpuacct'.
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return filepath.Join(raw.root, filepath.Base(mnt), raw.innerPath), nil
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}
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// Use GetOwnCgroupPath instead of GetInitCgroupPath, because the creating
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// process could in container and shared pid namespace with host, and
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// /proc/1/cgroup could point to whole other world of cgroups.
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parentPath, err := cgroups.GetOwnCgroupPath(subsystem)
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if err != nil {
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return "", err
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}
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return filepath.Join(parentPath, raw.innerPath), nil
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}
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func (raw *cgroupData) join(subsystem string) (string, error) {
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path, err := raw.path(subsystem)
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if err != nil {
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return "", err
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}
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if err := os.MkdirAll(path, 0755); err != nil {
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return "", err
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}
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if err := cgroups.WriteCgroupProc(path, raw.pid); err != nil {
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return "", err
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}
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return path, nil
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}
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func removePath(p string, err error) error {
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if err != nil {
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return err
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}
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if p != "" {
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return os.RemoveAll(p)
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}
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return nil
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}
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func (m *manager) GetPaths() map[string]string {
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m.mu.Lock()
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defer m.mu.Unlock()
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return m.paths
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}
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func (m *manager) GetCgroups() (*configs.Cgroup, error) {
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return m.cgroups, nil
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}
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func (m *manager) GetFreezerState() (configs.FreezerState, error) {
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dir := m.Path("freezer")
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// If the container doesn't have the freezer cgroup, say it's undefined.
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if dir == "" {
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return configs.Undefined, nil
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}
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freezer := &FreezerGroup{}
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return freezer.GetState(dir)
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}
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func (m *manager) Exists() bool {
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return cgroups.PathExists(m.Path("devices"))
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}
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