fs2: fix cgroup.subtree_control EPERM on rootless + add CI

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

.travis.yml

@@ -36,6 +36,8 @@ matrix:
         - sudo ssh default -t 'cd /vagrant && sudo make localintegration RUNC_USE_SYSTEMD=yes'
         # same setup but with fs2 driver instead of systemd
         - sudo ssh default -t 'cd /vagrant && sudo make localintegration'
+        # rootless
+        - sudo ssh default -t 'cd /vagrant && sudo make localrootlessintegration'
   allow_failures:
     - go: tip
 

libcontainer/cgroups/fs2/create.go

@@ -95,15 +95,22 @@ func CreateCgroupPath(path string, c *configs.Cgroup) (Err error) {
 					}
 				}()
 			}
+			// Write cgroup.type explicitly.
+			// Otherwise ENOTSUP may happen.
+			cgType := filepath.Join(current, "cgroup.type")
+			_ = ioutil.WriteFile(cgType, []byte("threaded"), 0644)
 		}
 		// enable needed controllers
 		if i < len(elements)-1 {
 			file := filepath.Join(current, "cgroup.subtree_control")
-			if err := ioutil.WriteFile(file, []byte(allCtrs), 0755); err != nil {
-				// XXX: we can enable _some_ controllers doing it one-by one
-				// instead of erroring out -- does it makes sense to do so?
-				return err
+			if err := ioutil.WriteFile(file, []byte(allCtrs), 0644); err != nil {
+				// try write one by one
+				for _, ctr := range ctrs {
+					_ = ioutil.WriteFile(file, []byte(ctr), 0644)
+				}
 			}
+			// Some controllers might not be enabled when rootless or containerized,
+			// but we don't catch the error here. (Caught in setXXX() functions.)
 		}
 	}
 

libcontainer/cgroups/fs2/fs2.go

@@ -53,7 +53,10 @@ func (m *manager) getControllers() error {
 
 	file := filepath.Join(m.dirPath, "cgroup.controllers")
 	data, err := ioutil.ReadFile(file)
-	if err != nil && !m.rootless {
+	if err != nil {
+		if m.rootless && m.config.Path == "" {
+			return nil
+		}
 		return err
 	}
 	fields := strings.Fields(string(data))
@@ -67,9 +70,22 @@ func (m *manager) getControllers() error {
 
 func (m *manager) Apply(pid int) error {
 	if err := CreateCgroupPath(m.dirPath, m.config); err != nil {
+		// Related tests:
+		// - "runc create (no limits + no cgrouppath + no permission) succeeds"
+		// - "runc create (rootless + no limits + cgrouppath + no permission) fails with permission error"
+		// - "runc create (rootless + limits + no cgrouppath + no permission) fails with informative error"
+		if m.rootless {
+			if m.config.Path == "" {
+				cl, clErr := neededControllers(m.config)
+				if clErr == nil && len(cl) == 0 {
+					return nil
+				}
+				return errors.Wrap(err, "rootless needs no limits + no cgrouppath when no permission is granted for cgroups")
+			}
+		}
 		return err
 	}
-	if err := cgroups.WriteCgroupProc(m.dirPath, pid); err != nil && !m.rootless {
+	if err := cgroups.WriteCgroupProc(m.dirPath, pid); err != nil {
 		return err
 	}
 	return nil
@@ -199,7 +215,11 @@ func (m *manager) Set(container *configs.Config) error {
 		}
 	}
 	// devices (since kernel 4.15, pseudo-controller)
-	if err := setDevices(m.dirPath, container.Cgroups); err != nil {
+	//
+	// When m.Rootless is true, errors from the device subsystem are ignored because it is really not expected to work.
+	// However, errors from other subsystems are not ignored.
+	// see @test "runc create (rootless + limits + no cgrouppath + no permission) fails with informative error"
+	if err := setDevices(m.dirPath, container.Cgroups); err != nil && !m.rootless {
 		errs = append(errs, err)
 	}
 	// cpuset (since kernel 5.0)
@@ -218,7 +238,7 @@ func (m *manager) Set(container *configs.Config) error {
 	if err := setFreezer(m.dirPath, container.Cgroups.Freezer); err != nil {
 		errs = append(errs, err)
 	}
-	if len(errs) > 0 && !m.rootless {
+	if len(errs) > 0 {
 		return errors.Errorf("error while setting cgroup v2: %+v", errs)
 	}
 	m.config = container.Cgroups

tests/integration/cgroups.bats

@@ -95,7 +95,7 @@ EOF
 
     runc run -d --console-socket $CONSOLE_SOCKET test_cgroups_permissions
     [ "$status" -eq 1 ]
-    [[ ${lines[1]} == *"cannot set pids limit: container could not join or create cgroup"* ]]
+    [[ ${lines[1]} == *"rootless needs no limits + no cgrouppath when no permission is granted for cgroups"* ]] || [[ ${lines[1]} == *"cannot set pids limit: container could not join or create cgroup"* ]]
 }
 
 @test "runc create (limits + cgrouppath + permission on the cgroup dir) succeeds" {

tests/integration/update.bats

@@ -68,6 +68,10 @@ EOF
 
     # check that initial values were properly set
     check_cgroup_value "cpuset.cpus" 0
+    if [[ "$CGROUP_UNIFIED" = "yes" ]] && ! grep -qw memory "$CGROUP_PATH/cgroup.controllers"; then
+    # This happen on containerized environment because "echo +memory > /sys/fs/cgroup/cgroup.subtree_control" fails with EINVAL
+        skip "memory controller not available"
+    fi
     check_cgroup_value $MEM_LIMIT 33554432
     check_cgroup_value $MEM_RESERVE 25165824
     check_cgroup_value "pids.max" 20

tests/rootless.sh

@@ -82,6 +82,27 @@ function enable_cgroup() {
 		# handling.
 		[[ "$cg" == "cpuset" ]] && chown rootless:rootless "$CGROUP_MOUNT/$cg$CGROUP_PATH/cpuset."{cpus,mems}
 	done
+	# cgroup v2
+	if [[ -e "$CGROUP_MOUNT/cgroup.controllers" ]]; then
+		# Enable controllers. Some controller (e.g. memory) may fail on containerized environment.
+		set -x
+		for f in $(cat "$CGROUP_MOUNT/cgroup.controllers"); do echo +$f > "$CGROUP_MOUNT/cgroup.subtree_control"; done
+		set +x
+		# Create the cgroup.
+		mkdir -p "$CGROUP_MOUNT/$CGROUP_PATH"
+		# chown/chmod dir + cgroup.subtree_control + cgroup.procs + parent's cgroup.procs.
+		# See https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#delegation-containment
+		chown root:rootless "$CGROUP_MOUNT/$CGROUP_PATH" "$CGROUP_MOUNT/$CGROUP_PATH/cgroup.subtree_control" "$CGROUP_MOUNT/$CGROUP_PATH/cgroup.procs" "$CGROUP_MOUNT/cgroup.procs"
+		chmod g+rwx "$CGROUP_MOUNT/$CGROUP_PATH"
+		chmod g+rw "$CGROUP_MOUNT/$CGROUP_PATH/cgroup.subtree_control" "$CGROUP_MOUNT/$CGROUP_PATH/cgroup.procs" "$CGROUP_MOUNT/cgroup.procs"
+		# Fix up cgroup.type.
+		echo threaded > "$CGROUP_MOUNT/$CGROUP_PATH/cgroup.type"
+		# Make sure cgroup.type doesn't contain "invalid". Otherwise write ops will fail with ENOTSUP.
+		# See http://man7.org/linux/man-pages/man7/cgroups.7.html
+		if grep -qw invalid "$CGROUP_MOUNT/$CGROUP_PATH/cgroup.type"; then
+			exit 1
+		fi
+	fi
 }
 
 function disable_cgroup() {
@@ -90,6 +111,8 @@ function disable_cgroup() {
 	do
 		[ -d "$CGROUP_MOUNT/$cg$CGROUP_PATH" ] && rmdir "$CGROUP_MOUNT/$cg$CGROUP_PATH"
 	done
+	# cgroup v2
+	[ -d "$CGROUP_MOUNT/$CGROUP_PATH" ] && rmdir "$CGROUP_MOUNT/$CGROUP_PATH"
 }
 
 # Create a powerset of $ALL_FEATURES (the set of all subsets of $ALL_FEATURES).