Plumb VFS2 inside the Sentry

- Added fsbridge package with interface that can be used to open
  and read from VFS1 and VFS2 files.
- Converted ELF loader to use fsbridge
- Added VFS2 types to FSContext
- Added vfs.MountNamespace to ThreadGroup

Updates #1623

PiperOrigin-RevId: 295183950

3 files changed, 20 insertions, 16 deletions

diff --git a/pkg/sentry/fsimpl/proc/BUILD b/pkg/sentry/fsimpl/proc/BUILD
index 12aac2e6a..a83245866 100644
--- a/pkg/sentry/fsimpl/proc/BUILD
+++ b/pkg/sentry/fsimpl/proc/BUILD
@@ -14,6 +14,7 @@ go_library(
         "tasks_net.go",
         "tasks_sys.go",
     ],
+    visibility = ["//pkg/sentry:internal"],
     deps = [
         "//pkg/abi/linux",
         "//pkg/context",
diff --git a/pkg/sentry/fsimpl/proc/filesystem.go b/pkg/sentry/fsimpl/proc/filesystem.go
index 11477b6a9..5c19d5522 100644
--- a/pkg/sentry/fsimpl/proc/filesystem.go
+++ b/pkg/sentry/fsimpl/proc/filesystem.go
@@ -26,15 +26,18 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 )
 
-// procFSType is the factory class for procfs.
+// Name is the default filesystem name.
+const Name = "proc"
+
+// FilesystemType is the factory class for procfs.
 //
 // +stateify savable
-type procFSType struct{}
+type FilesystemType struct{}
 
-var _ vfs.FilesystemType = (*procFSType)(nil)
+var _ vfs.FilesystemType = (*FilesystemType)(nil)
 
 // GetFilesystem implements vfs.FilesystemType.
-func (ft *procFSType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
+func (ft *FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
 	k := kernel.KernelFromContext(ctx)
 	if k == nil {
 		return nil, nil, fmt.Errorf("procfs requires a kernel")
@@ -47,12 +50,13 @@ func (ft *procFSType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFile
 	procfs := &kernfs.Filesystem{}
 	procfs.VFSFilesystem().Init(vfsObj, procfs)
 
-	var data *InternalData
+	var cgroups map[string]string
 	if opts.InternalData != nil {
-		data = opts.InternalData.(*InternalData)
+		data := opts.InternalData.(*InternalData)
+		cgroups = data.Cgroups
 	}
 
-	_, dentry := newTasksInode(procfs, k, pidns, data.Cgroups)
+	_, dentry := newTasksInode(procfs, k, pidns, cgroups)
 	return procfs.VFSFilesystem(), dentry.VFSDentry(), nil
 }
 
diff --git a/pkg/sentry/fsimpl/proc/tasks_test.go b/pkg/sentry/fsimpl/proc/tasks_test.go
index 6fc3524db..96c72cbc9 100644
--- a/pkg/sentry/fsimpl/proc/tasks_test.go
+++ b/pkg/sentry/fsimpl/proc/tasks_test.go
@@ -90,8 +90,7 @@ func setup(t *testing.T) *testutil.System {
 	ctx := k.SupervisorContext()
 	creds := auth.CredentialsFromContext(ctx)
 
-	vfsObj := vfs.New()
-	vfsObj.MustRegisterFilesystemType("procfs", &procFSType{}, &vfs.RegisterFilesystemTypeOptions{
+	k.VFS.MustRegisterFilesystemType(Name, &FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
 		AllowUserMount: true,
 	})
 	fsOpts := vfs.GetFilesystemOptions{
@@ -102,11 +101,11 @@ func setup(t *testing.T) *testutil.System {
 			},
 		},
 	}
-	mntns, err := vfsObj.NewMountNamespace(ctx, creds, "", "procfs", &fsOpts)
+	mntns, err := k.VFS.NewMountNamespace(ctx, creds, "", Name, &fsOpts)
 	if err != nil {
 		t.Fatalf("NewMountNamespace(): %v", err)
 	}
-	return testutil.NewSystem(ctx, t, vfsObj, mntns)
+	return testutil.NewSystem(ctx, t, k.VFS, mntns)
 }
 
 func TestTasksEmpty(t *testing.T) {
@@ -131,7 +130,7 @@ func TestTasks(t *testing.T) {
 	var tasks []*kernel.Task
 	for i := 0; i < 5; i++ {
 		tc := k.NewThreadGroup(nil, k.RootPIDNamespace(), kernel.NewSignalHandlers(), linux.SIGCHLD, k.GlobalInit().Limits())
-		task, err := testutil.CreateTask(s.Ctx, fmt.Sprintf("name-%d", i), tc)
+		task, err := testutil.CreateTask(s.Ctx, fmt.Sprintf("name-%d", i), tc, s.MntNs, s.Root, s.Root)
 		if err != nil {
 			t.Fatalf("CreateTask(): %v", err)
 		}
@@ -213,7 +212,7 @@ func TestTasksOffset(t *testing.T) {
 	k := kernel.KernelFromContext(s.Ctx)
 	for i := 0; i < 3; i++ {
 		tc := k.NewThreadGroup(nil, k.RootPIDNamespace(), kernel.NewSignalHandlers(), linux.SIGCHLD, k.GlobalInit().Limits())
-		if _, err := testutil.CreateTask(s.Ctx, fmt.Sprintf("name-%d", i), tc); err != nil {
+		if _, err := testutil.CreateTask(s.Ctx, fmt.Sprintf("name-%d", i), tc, s.MntNs, s.Root, s.Root); err != nil {
 			t.Fatalf("CreateTask(): %v", err)
 		}
 	}
@@ -337,7 +336,7 @@ func TestTask(t *testing.T) {
 
 	k := kernel.KernelFromContext(s.Ctx)
 	tc := k.NewThreadGroup(nil, k.RootPIDNamespace(), kernel.NewSignalHandlers(), linux.SIGCHLD, k.GlobalInit().Limits())
-	_, err := testutil.CreateTask(s.Ctx, "name", tc)
+	_, err := testutil.CreateTask(s.Ctx, "name", tc, s.MntNs, s.Root, s.Root)
 	if err != nil {
 		t.Fatalf("CreateTask(): %v", err)
 	}
@@ -352,7 +351,7 @@ func TestProcSelf(t *testing.T) {
 
 	k := kernel.KernelFromContext(s.Ctx)
 	tc := k.NewThreadGroup(nil, k.RootPIDNamespace(), kernel.NewSignalHandlers(), linux.SIGCHLD, k.GlobalInit().Limits())
-	task, err := testutil.CreateTask(s.Ctx, "name", tc)
+	task, err := testutil.CreateTask(s.Ctx, "name", tc, s.MntNs, s.Root, s.Root)
 	if err != nil {
 		t.Fatalf("CreateTask(): %v", err)
 	}
@@ -433,7 +432,7 @@ func TestTree(t *testing.T) {
 	var tasks []*kernel.Task
 	for i := 0; i < 5; i++ {
 		tc := k.NewThreadGroup(nil, k.RootPIDNamespace(), kernel.NewSignalHandlers(), linux.SIGCHLD, k.GlobalInit().Limits())
-		task, err := testutil.CreateTask(s.Ctx, fmt.Sprintf("name-%d", i), tc)
+		task, err := testutil.CreateTask(s.Ctx, fmt.Sprintf("name-%d", i), tc, s.MntNs, s.Root, s.Root)
 		if err != nil {
 			t.Fatalf("CreateTask(): %v", err)
 		}