Bump Libcontainer to latest head

vendor/github.com/opencontainers/runc/libcontainer/cgroups/utils.go

@@ -16,13 +16,19 @@ import (
 	"github.com/docker/go-units"
 )
 
-const cgroupNamePrefix = "name="
+const (
+	cgroupNamePrefix = "name="
+	CgroupProcesses  = "cgroup.procs"
+)
 
-// https://www.kernel.org/doc/Documentation/cgroups/cgroups.txt
+// https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt
 func FindCgroupMountpoint(subsystem string) (string, error) {
 	// We are not using mount.GetMounts() because it's super-inefficient,
 	// parsing it directly sped up x10 times because of not using Sscanf.
 	// It was one of two major performance drawbacks in container start.
+	if !isSubsystemAvailable(subsystem) {
+		return "", NewNotFoundError(subsystem)
+	}
 	f, err := os.Open("/proc/self/mountinfo")
 	if err != nil {
 		return "", err
@@ -47,6 +53,9 @@ func FindCgroupMountpoint(subsystem string) (string, error) {
 }
 
 func FindCgroupMountpointAndRoot(subsystem string) (string, string, error) {
+	if !isSubsystemAvailable(subsystem) {
+		return "", "", NewNotFoundError(subsystem)
+	}
 	f, err := os.Open("/proc/self/mountinfo")
 	if err != nil {
 		return "", "", err
@@ -70,6 +79,15 @@ func FindCgroupMountpointAndRoot(subsystem string) (string, string, error) {
 	return "", "", NewNotFoundError(subsystem)
 }
 
+func isSubsystemAvailable(subsystem string) bool {
+	cgroups, err := ParseCgroupFile("/proc/self/cgroup")
+	if err != nil {
+		return false
+	}
+	_, avail := cgroups[subsystem]
+	return avail
+}
+
 func FindCgroupMountpointDir() (string, error) {
 	f, err := os.Open("/proc/self/mountinfo")
 	if err != nil {
@@ -124,7 +142,8 @@ func (m Mount) GetThisCgroupDir(cgroups map[string]string) (string, error) {
 func getCgroupMountsHelper(ss map[string]bool, mi io.Reader) ([]Mount, error) {
 	res := make([]Mount, 0, len(ss))
 	scanner := bufio.NewScanner(mi)
-	for scanner.Scan() {
+	numFound := 0
+	for scanner.Scan() && numFound < len(ss) {
 		txt := scanner.Text()
 		sepIdx := strings.Index(txt, " - ")
 		if sepIdx == -1 {
@@ -139,12 +158,15 @@ func getCgroupMountsHelper(ss map[string]bool, mi io.Reader) ([]Mount, error) {
 			Root:       fields[3],
 		}
 		for _, opt := range strings.Split(fields[len(fields)-1], ",") {
+			if !ss[opt] {
+				continue
+			}
 			if strings.HasPrefix(opt, cgroupNamePrefix) {
 				m.Subsystems = append(m.Subsystems, opt[len(cgroupNamePrefix):])
-			}
-			if ss[opt] {
+			} else {
 				m.Subsystems = append(m.Subsystems, opt)
 			}
+			numFound++
 		}
 		res = append(res, m)
 	}
@@ -161,19 +183,19 @@ func GetCgroupMounts() ([]Mount, error) {
 	}
 	defer f.Close()
 
-	all, err := GetAllSubsystems()
+	all, err := ParseCgroupFile("/proc/self/cgroup")
 	if err != nil {
 		return nil, err
 	}
 
 	allMap := make(map[string]bool)
-	for _, s := range all {
+	for s := range all {
 		allMap[s] = true
 	}
 	return getCgroupMountsHelper(allMap, f)
 }
 
-// Returns all the cgroup subsystems supported by the kernel
+// GetAllSubsystems returns all the cgroup subsystems supported by the kernel
 func GetAllSubsystems() ([]string, error) {
 	f, err := os.Open("/proc/cgroups")
 	if err != nil {
@@ -199,7 +221,7 @@ func GetAllSubsystems() ([]string, error) {
 	return subsystems, nil
 }
 
-// Returns the relative path to the cgroup docker is running in.
+// GetThisCgroupDir returns the relative path to the cgroup docker is running in.
 func GetThisCgroupDir(subsystem string) (string, error) {
 	cgroups, err := ParseCgroupFile("/proc/self/cgroup")
 	if err != nil {
@@ -220,7 +242,7 @@ func GetInitCgroupDir(subsystem string) (string, error) {
 }
 
 func readProcsFile(dir string) ([]int, error) {
-	f, err := os.Open(filepath.Join(dir, "cgroup.procs"))
+	f, err := os.Open(filepath.Join(dir, CgroupProcesses))
 	if err != nil {
 		return nil, err
 	}
@@ -243,6 +265,8 @@ func readProcsFile(dir string) ([]int, error) {
 	return out, nil
 }
 
+// ParseCgroupFile parses the given cgroup file, typically from
+// /proc/<pid>/cgroup, into a map of subgroups to cgroup names.
 func ParseCgroupFile(path string) (map[string]string, error) {
 	f, err := os.Open(path)
 	if err != nil {
@@ -250,7 +274,12 @@ func ParseCgroupFile(path string) (map[string]string, error) {
 	}
 	defer f.Close()
 
-	s := bufio.NewScanner(f)
+	return parseCgroupFromReader(f)
+}
+
+// helper function for ParseCgroupFile to make testing easier
+func parseCgroupFromReader(r io.Reader) (map[string]string, error) {
+	s := bufio.NewScanner(r)
 	cgroups := make(map[string]string)
 
 	for s.Scan() {
@@ -259,7 +288,16 @@ func ParseCgroupFile(path string) (map[string]string, error) {
 		}
 
 		text := s.Text()
-		parts := strings.Split(text, ":")
+		// from cgroups(7):
+		// /proc/[pid]/cgroup
+		// ...
+		// For each cgroup hierarchy ... there is one entry
+		// containing three colon-separated fields of the form:
+		//     hierarchy-ID:subsystem-list:cgroup-path
+		parts := strings.SplitN(text, ":", 3)
+		if len(parts) < 3 {
+			return nil, fmt.Errorf("invalid cgroup entry: must contain at least two colons: %v", text)
+		}
 
 		for _, subs := range strings.Split(parts[1], ",") {
 			cgroups[subs] = parts[2]
@@ -291,8 +329,7 @@ func PathExists(path string) bool {
 func EnterPid(cgroupPaths map[string]string, pid int) error {
 	for _, path := range cgroupPaths {
 		if PathExists(path) {
-			if err := ioutil.WriteFile(filepath.Join(path, "cgroup.procs"),
-				[]byte(strconv.Itoa(pid)), 0700); err != nil {
+			if err := WriteCgroupProc(path, pid); err != nil {
 				return err
 			}
 		}
@@ -361,7 +398,7 @@ func GetAllPids(path string) ([]int, error) {
 	// collect pids from all sub-cgroups
 	err := filepath.Walk(path, func(p string, info os.FileInfo, iErr error) error {
 		dir, file := filepath.Split(p)
-		if file != "cgroup.procs" {
+		if file != CgroupProcesses {
 			return nil
 		}
 		if iErr != nil {
@@ -376,3 +413,20 @@ func GetAllPids(path string) ([]int, error) {
 	})
 	return pids, err
 }
+
+// WriteCgroupProc writes the specified pid into the cgroup's cgroup.procs file
+func WriteCgroupProc(dir string, pid int) error {
+	// Normally dir should not be empty, one case is that cgroup subsystem
+	// is not mounted, we will get empty dir, and we want it fail here.
+	if dir == "" {
+		return fmt.Errorf("no such directory for %s", CgroupProcesses)
+	}
+
+	// Dont attach any pid to the cgroup if -1 is specified as a pid
+	if pid != -1 {
+		if err := ioutil.WriteFile(filepath.Join(dir, CgroupProcesses), []byte(strconv.Itoa(pid)), 0700); err != nil {
+			return fmt.Errorf("failed to write %v to %v: %v", pid, CgroupProcesses, err)
+		}
+	}
+	return nil
+}