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Make /sys/fs/cgroup writable when non-privileged and using cgroups v2 #5277

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Merged
openshift-merge-robot merged 1 commit into from
Oct 27, 2021
Merged

Make /sys/fs/cgroup writable when non-privileged and using cgroups v2 #5277

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4 changes: 4 additions & 0 deletions pkg/annotations/annotations.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,9 @@ const (
// UsernsMode is the user namespace mode to use
UsernsModeAnnotation = "io.kubernetes.cri-o.userns-mode"

// CgroupRW specifies mounting v2 cgroups as an rw filesystem.
Cgroup2RWAnnotation = "io.kubernetes.cri-o.cgroup2-mount-hierarchy-rw"

// UnifiedCgroupAnnotation specifies the unified configuration for cgroup v2
UnifiedCgroupAnnotation = "io.kubernetes.cri-o.UnifiedCgroup"

Expand Down Expand Up @@ -39,6 +42,7 @@ const (

var AllAllowedAnnotations = []string{
UsernsModeAnnotation,
Cgroup2RWAnnotation,
UnifiedCgroupAnnotation,
ShmSizeAnnotation,
DevicesAnnotation,
Expand Down
1 change: 1 addition & 0 deletions pkg/config/template.go
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Expand Up @@ -1005,6 +1005,7 @@ const templateStringCrioRuntimeRuntimesRuntimeHandler = `# The "crio.runtime.run
# a list of experimental annotations that this runtime handler is allowed to process.
# The currently recognized values are:
# "io.kubernetes.cri-o.userns-mode" for configuring a user namespace for the pod.
# "io.kubernetes.cri-o.cgroup2-mount-hierarchy-rw" for mounting cgroups writably when set to "true".
# "io.kubernetes.cri-o.Devices" for configuring devices for the pod.
# "io.kubernetes.cri-o.ShmSize" for configuring the size of /dev/shm.
# "io.kubernetes.cri-o.UnifiedCgroup.$CTR_NAME" for configuring the cgroup v2 unified block for a container.
Expand Down
14 changes: 11 additions & 3 deletions server/container_create_linux.go
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Expand Up @@ -291,7 +291,9 @@ func (s *Server) createSandboxContainer(ctx context.Context, ctr ctrIface.Contai
skipRelabel = true
}

containerVolumes, ociMounts, err := addOCIBindMounts(ctx, ctr, mountLabel, s.config.RuntimeConfig.BindMountPrefix, s.config.AbsentMountSourcesToReject, maybeRelabel, skipRelabel)
cgroup2RW := node.CgroupIsV2() && sb.Annotations()[crioann.Cgroup2RWAnnotation] == "true"

containerVolumes, ociMounts, err := addOCIBindMounts(ctx, ctr, mountLabel, s.config.RuntimeConfig.BindMountPrefix, s.config.AbsentMountSourcesToReject, maybeRelabel, skipRelabel, cgroup2RW)
if err != nil {
return nil, err
}
Expand Down Expand Up @@ -843,7 +845,7 @@ func clearReadOnly(m *rspec.Mount) {
m.Options = append(m.Options, "rw")
}

func addOCIBindMounts(ctx context.Context, ctr ctrIface.Container, mountLabel, bindMountPrefix string, absentMountSourcesToReject []string, maybeRelabel, skipRelabel bool) ([]oci.ContainerVolume, []rspec.Mount, error) {
func addOCIBindMounts(ctx context.Context, ctr ctrIface.Container, mountLabel, bindMountPrefix string, absentMountSourcesToReject []string, maybeRelabel, skipRelabel, cgroup2RW bool) ([]oci.ContainerVolume, []rspec.Mount, error) {
volumes := []oci.ContainerVolume{}
ociMounts := []rspec.Mount{}
containerConfig := ctr.Config()
Expand Down Expand Up @@ -978,7 +980,13 @@ func addOCIBindMounts(ctx context.Context, ctr ctrIface.Container, mountLabel, b
Destination: "/sys/fs/cgroup",
Type: "cgroup",
Source: "cgroup",
Options: []string{"nosuid", "noexec", "nodev", "relatime", "ro"},
Options: []string{"nosuid", "noexec", "nodev", "relatime"},
}

if cgroup2RW {
m.Options = append(m.Options, "rw")
} else {
m.Options = append(m.Options, "ro")
}
specgen.AddMount(m)
}
Expand Down
73 changes: 71 additions & 2 deletions server/container_create_linux_test.go
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Expand Up @@ -34,7 +34,7 @@ func TestAddOCIBindsForDev(t *testing.T) {
t.Error(err)
}

_, binds, err := addOCIBindMounts(context.Background(), ctr, "", "", nil, false, false)
_, binds, err := addOCIBindMounts(context.Background(), ctr, "", "", nil, false, false, false)
if err != nil {
t.Error(err)
}
Expand Down Expand Up @@ -78,7 +78,7 @@ func TestAddOCIBindsForSys(t *testing.T) {
t.Error(err)
}

_, binds, err := addOCIBindMounts(context.Background(), ctr, "", "", nil, false, false)
_, binds, err := addOCIBindMounts(context.Background(), ctr, "", "", nil, false, false, false)
if err != nil {
t.Error(err)
}
Expand All @@ -92,3 +92,72 @@ func TestAddOCIBindsForSys(t *testing.T) {
t.Error("there is not a single /sys bind mount")
}
}

func TestAddOCIBindsCGroupRW(t *testing.T) {
ctr, err := container.New()
if err != nil {
t.Error(err)
}

if err := ctr.SetConfig(&types.ContainerConfig{
Metadata: &types.ContainerMetadata{
Name: "testctr",
},
}, &types.PodSandboxConfig{
Metadata: &types.PodSandboxMetadata{
Name: "testpod",
},
}); err != nil {
t.Error(err)
}
_, _, err = addOCIBindMounts(context.Background(), ctr, "", "", nil, false, false, true)
if err != nil {
t.Error(err)
}
var hasCgroupRW bool
for _, m := range ctr.Spec().Mounts() {
if m.Destination == "/sys/fs/cgroup" {
for _, o := range m.Options {
if o == "rw" {
hasCgroupRW = true
}
}
}
}
if !hasCgroupRW {
t.Error("Cgroup mount not added with RW.")
}

ctr, err = container.New()
if err != nil {
t.Error(err)
}
if err := ctr.SetConfig(&types.ContainerConfig{
Metadata: &types.ContainerMetadata{
Name: "testctr",
},
}, &types.PodSandboxConfig{
Metadata: &types.PodSandboxMetadata{
Name: "testpod",
},
}); err != nil {
t.Error(err)
}
var hasCgroupRO bool
_, _, err = addOCIBindMounts(context.Background(), ctr, "", "", nil, false, false, false)
if err != nil {
t.Error(err)
}
for _, m := range ctr.Spec().Mounts() {
if m.Destination == "/sys/fs/cgroup" {
for _, o := range m.Options {
if o == "ro" {
hasCgroupRO = true
}
}
}
}
if !hasCgroupRO {
t.Error("Cgroup mount not added with RO.")
}
}