Add a unique id per cgroup.

PiperOrigin-RevId: 540031470

pkg/sentry/fsimpl/cgroupfs/base.go

@@ -25,6 +25,7 @@ import (
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/hostarch"
+	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
@@ -151,6 +152,9 @@ type controller interface {
 type cgroupInode struct {
 	dir
 
+	// id is the id of this cgroup.
+	id uint32
+
 	// controllers is the set of controllers for this cgroup. This is used to
 	// store controller-specific state per cgroup. The set of controllers should
 	// match the controllers for this hierarchy as tracked by the filesystem
@@ -175,6 +179,16 @@ func (fs *filesystem) newCgroupInode(ctx context.Context, creds *auth.Credential
 	}
 	c.dir.cgi = c
 
+	k := kernel.KernelFromContext(ctx)
+	r := k.CgroupRegistry()
+	// Assign id for the cgroup.
+	cid, err := r.NextCgroupID()
+	if err != nil {
+		log.Warningf("cgroupfs newCgroupInode: Failed to assign id to the cgroup: %v", err)
+	}
+	c.id = cid
+	r.AddCgroup(c)
+
 	contents := make(map[string]kernfs.Inode)
 	contents["cgroup.procs"] = fs.newControllerWritableFile(ctx, creds, &cgroupProcsData{c}, false)
 	contents["tasks"] = fs.newControllerWritableFile(ctx, creds, &tasksData{c}, false)
@@ -382,6 +396,11 @@ func (c *cgroupInode) WriteControl(ctx context.Context, name string, value strin
 	return nil
 }
 
+// ID implements kernel.CgroupImpl.ID.
+func (c *cgroupInode) ID() uint32 {
+	return c.id
+}
+
 func sortTIDs(tids []kernel.ThreadID) {
 	sort.Slice(tids, func(i, j int) bool { return tids[i] < tids[j] })
 }

pkg/sentry/kernel/cgroup.go

@@ -31,6 +31,9 @@ import (
 // InvalidCgroupHierarchyID indicates an uninitialized hierarchy ID.
 const InvalidCgroupHierarchyID uint32 = 0
 
+// InvalidCgroupID indicates an uninitialized cgroup ID.
+const InvalidCgroupID uint32 = 0
+
 // CgroupControllerType is the name of a cgroup controller.
 type CgroupControllerType string
 
@@ -212,6 +215,9 @@ type CgroupImpl interface {
 	// WriteControl allows a background context to write a cgroup's control
 	// values.
 	WriteControl(ctx context.Context, name string, val string) error
+
+	// ID returns the id of this cgroup.
+	ID() uint32
 }
 
 // hierarchy represents a cgroupfs filesystem instance, with a unique set of
@@ -268,6 +274,11 @@ type CgroupRegistry struct {
 	//
 	lastHierarchyID atomicbitops.Uint32
 
+	// lastCgroupID is the id of the last allocated cgroup. Valid ids are
+	// from 1 to math.MaxUint32.
+	//
+	lastCgroupID atomicbitops.Uint32
+
 	mu cgroupMutex `state:"nosave"`
 
 	// controllers is the set of currently known cgroup controllers on the
@@ -287,6 +298,12 @@ type CgroupRegistry struct {
 	//
 	// +checklocks:mu
 	hierarchiesByName map[string]hierarchy
+
+	// cgroups is the active set of cgroups. This contains all the cgroups
+	// on the system.
+	//
+	// +checklocks:mu
+	cgroups map[uint32]CgroupImpl
 }
 
 func newCgroupRegistry() *CgroupRegistry {
@@ -294,6 +311,7 @@ func newCgroupRegistry() *CgroupRegistry {
 		controllers:       make(map[CgroupControllerType]CgroupController),
 		hierarchies:       make(map[uint32]hierarchy),
 		hierarchiesByName: make(map[string]hierarchy),
+		cgroups:           make(map[uint32]CgroupImpl),
 	}
 }
 
@@ -512,3 +530,29 @@ func (r *CgroupRegistry) GenerateProcCgroups(buf *bytes.Buffer) {
 		fmt.Fprint(buf, e)
 	}
 }
+
+// NextCgroupID returns a newly allocated, unique cgroup ID.
+func (r *CgroupRegistry) NextCgroupID() (uint32, error) {
+	if cid := r.lastCgroupID.Add(1); cid != 0 {
+		return cid, nil
+	}
+	return InvalidCgroupID, fmt.Errorf("cgroup ID overflow")
+}
+
+// AddCgroup adds the ID and cgroup in the map.
+func (r *CgroupRegistry) AddCgroup(cg CgroupImpl) {
+	r.mu.Lock()
+	r.cgroups[cg.ID()] = cg
+	r.mu.Unlock()
+}
+
+// GetCgroup returns the cgroup associated with the cgroup ID.
+func (r *CgroupRegistry) GetCgroup(cid uint32) (CgroupImpl, error) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	cg, ok := r.cgroups[cid]
+	if !ok {
+		return nil, fmt.Errorf("cgroup with ID %d does not exist", cid)
+	}
+	return cg, nil
+}