[vfs] kernfs: Implement remaining InodeAttr fields.

Added the following fields in kernfs.InodeAttr:
- blockSize
- atime
- mtime
- ctime

Also resolved all TODOs for #1193.

Fixes #1193

PiperOrigin-RevId: 338714527

9 files changed, 121 insertions, 77 deletions

diff --git a/pkg/sentry/fsimpl/kernfs/BUILD b/pkg/sentry/fsimpl/kernfs/BUILD
index dbb70a875..4de1e6922 100644
--- a/pkg/sentry/fsimpl/kernfs/BUILD
+++ b/pkg/sentry/fsimpl/kernfs/BUILD
@@ -107,6 +107,7 @@ go_library(
         "//pkg/refsvfs2",
         "//pkg/sentry/fs/lock",
         "//pkg/sentry/kernel/auth",
+        "//pkg/sentry/kernel/time",
         "//pkg/sentry/memmap",
         "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/vfs",
diff --git a/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go b/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
index b929118b1..485504995 100644
--- a/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
+++ b/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
@@ -47,11 +47,11 @@ type DynamicBytesFile struct {
 var _ Inode = (*DynamicBytesFile)(nil)
 
 // Init initializes a dynamic bytes file.
-func (f *DynamicBytesFile) Init(creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, data vfs.DynamicBytesSource, perm linux.FileMode) {
+func (f *DynamicBytesFile) Init(ctx context.Context, creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, data vfs.DynamicBytesSource, perm linux.FileMode) {
 	if perm&^linux.PermissionsMask != 0 {
 		panic(fmt.Sprintf("Only permission mask must be set: %x", perm&linux.PermissionsMask))
 	}
-	f.InodeAttrs.Init(creds, devMajor, devMinor, ino, linux.ModeRegular|perm)
+	f.InodeAttrs.Init(ctx, creds, devMajor, devMinor, ino, linux.ModeRegular|perm)
 	f.data = data
 }
 
diff --git a/pkg/sentry/fsimpl/kernfs/fd_impl_util.go b/pkg/sentry/fsimpl/kernfs/fd_impl_util.go
index abf1905d6..38503c90d 100644
--- a/pkg/sentry/fsimpl/kernfs/fd_impl_util.go
+++ b/pkg/sentry/fsimpl/kernfs/fd_impl_util.go
@@ -219,7 +219,7 @@ func (fd *GenericDirectoryFD) IterDirents(ctx context.Context, cb vfs.IterDirent
 
 	var err error
 	relOffset := fd.off - int64(len(fd.children.set)) - 2
-	fd.off, err = fd.inode().IterDirents(ctx, cb, fd.off, relOffset)
+	fd.off, err = fd.inode().IterDirents(ctx, fd.vfsfd.Mount(), cb, fd.off, relOffset)
 	return err
 }
 
diff --git a/pkg/sentry/fsimpl/kernfs/filesystem.go b/pkg/sentry/fsimpl/kernfs/filesystem.go
index 6426a55f6..399895f3e 100644
--- a/pkg/sentry/fsimpl/kernfs/filesystem.go
+++ b/pkg/sentry/fsimpl/kernfs/filesystem.go
@@ -373,7 +373,7 @@ func (fs *Filesystem) MkdirAt(ctx context.Context, rp *vfs.ResolvingPath, opts v
 		if !opts.ForSyntheticMountpoint || err == syserror.EEXIST {
 			return err
 		}
-		childI = newSyntheticDirectory(rp.Credentials(), opts.Mode)
+		childI = newSyntheticDirectory(ctx, rp.Credentials(), opts.Mode)
 	}
 	var child Dentry
 	child.Init(fs, childI)
@@ -517,9 +517,6 @@ afterTrailingSymlink:
 		}
 		var child Dentry
 		child.Init(fs, childI)
-		// FIXME(gvisor.dev/issue/1193): Race between checking existence with
-		// fs.stepExistingLocked and parent.insertChild. If possible, we should hold
-		// dirMu from one to the other.
 		parent.insertChild(pc, &child)
 		// Open may block so we need to unlock fs.mu. IncRef child to prevent
 		// its destruction while fs.mu is unlocked.
diff --git a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
index 122b10591..d9d76758a 100644
--- a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
+++ b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
@@ -21,9 +21,11 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/usermem"
 )
 
 // InodeNoopRefCount partially implements the Inode interface, specifically the
@@ -143,7 +145,7 @@ func (InodeNotDirectory) Lookup(ctx context.Context, name string) (Inode, error)
 }
 
 // IterDirents implements Inode.IterDirents.
-func (InodeNotDirectory) IterDirents(ctx context.Context, callback vfs.IterDirentsCallback, offset, relOffset int64) (newOffset int64, err error) {
+func (InodeNotDirectory) IterDirents(ctx context.Context, mnt *vfs.Mount, callback vfs.IterDirentsCallback, offset, relOffset int64) (newOffset int64, err error) {
 	panic("IterDirents called on non-directory inode")
 }
 
@@ -172,17 +174,23 @@ func (InodeNotSymlink) Getlink(context.Context, *vfs.Mount) (vfs.VirtualDentry,
 //
 // +stateify savable
 type InodeAttrs struct {
-	devMajor uint32
-	devMinor uint32
-	ino      uint64
-	mode     uint32
-	uid      uint32
-	gid      uint32
-	nlink    uint32
+	devMajor  uint32
+	devMinor  uint32
+	ino       uint64
+	mode      uint32
+	uid       uint32
+	gid       uint32
+	nlink     uint32
+	blockSize uint32
+
+	// Timestamps, all nsecs from the Unix epoch.
+	atime int64
+	mtime int64
+	ctime int64
 }
 
 // Init initializes this InodeAttrs.
-func (a *InodeAttrs) Init(creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, mode linux.FileMode) {
+func (a *InodeAttrs) Init(ctx context.Context, creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, mode linux.FileMode) {
 	if mode.FileType() == 0 {
 		panic(fmt.Sprintf("No file type specified in 'mode' for InodeAttrs.Init(): mode=0%o", mode))
 	}
@@ -198,6 +206,11 @@ func (a *InodeAttrs) Init(creds *auth.Credentials, devMajor, devMinor uint32, in
 	atomic.StoreUint32(&a.uid, uint32(creds.EffectiveKUID))
 	atomic.StoreUint32(&a.gid, uint32(creds.EffectiveKGID))
 	atomic.StoreUint32(&a.nlink, nlink)
+	atomic.StoreUint32(&a.blockSize, usermem.PageSize)
+	now := ktime.NowFromContext(ctx).Nanoseconds()
+	atomic.StoreInt64(&a.atime, now)
+	atomic.StoreInt64(&a.mtime, now)
+	atomic.StoreInt64(&a.ctime, now)
 }
 
 // DevMajor returns the device major number.
@@ -220,12 +233,33 @@ func (a *InodeAttrs) Mode() linux.FileMode {
 	return linux.FileMode(atomic.LoadUint32(&a.mode))
 }
 
+// TouchAtime updates a.atime to the current time.
+func (a *InodeAttrs) TouchAtime(ctx context.Context, mnt *vfs.Mount) {
+	if mnt.Flags.NoATime || mnt.ReadOnly() {
+		return
+	}
+	if err := mnt.CheckBeginWrite(); err != nil {
+		return
+	}
+	atomic.StoreInt64(&a.atime, ktime.NowFromContext(ctx).Nanoseconds())
+	mnt.EndWrite()
+}
+
+// TouchCMtime updates a.{c/m}time to the current time. The caller should
+// synchronize calls to this so that ctime and mtime are updated to the same
+// value.
+func (a *InodeAttrs) TouchCMtime(ctx context.Context) {
+	now := ktime.NowFromContext(ctx).Nanoseconds()
+	atomic.StoreInt64(&a.mtime, now)
+	atomic.StoreInt64(&a.ctime, now)
+}
+
 // Stat partially implements Inode.Stat. Note that this function doesn't provide
 // all the stat fields, and the embedder should consider extending the result
 // with filesystem-specific fields.
 func (a *InodeAttrs) Stat(context.Context, *vfs.Filesystem, vfs.StatOptions) (linux.Statx, error) {
 	var stat linux.Statx
-	stat.Mask = linux.STATX_TYPE | linux.STATX_MODE | linux.STATX_UID | linux.STATX_GID | linux.STATX_INO | linux.STATX_NLINK
+	stat.Mask = linux.STATX_TYPE | linux.STATX_MODE | linux.STATX_UID | linux.STATX_GID | linux.STATX_INO | linux.STATX_NLINK | linux.STATX_ATIME | linux.STATX_MTIME | linux.STATX_CTIME
 	stat.DevMajor = a.devMajor
 	stat.DevMinor = a.devMinor
 	stat.Ino = atomic.LoadUint64(&a.ino)
@@ -233,21 +267,15 @@ func (a *InodeAttrs) Stat(context.Context, *vfs.Filesystem, vfs.StatOptions) (li
 	stat.UID = atomic.LoadUint32(&a.uid)
 	stat.GID = atomic.LoadUint32(&a.gid)
 	stat.Nlink = atomic.LoadUint32(&a.nlink)
-
-	// TODO(gvisor.dev/issue/1193): Implement other stat fields like timestamps.
-
+	stat.Blksize = atomic.LoadUint32(&a.blockSize)
+	stat.Atime = linux.NsecToStatxTimestamp(atomic.LoadInt64(&a.atime))
+	stat.Mtime = linux.NsecToStatxTimestamp(atomic.LoadInt64(&a.mtime))
+	stat.Ctime = linux.NsecToStatxTimestamp(atomic.LoadInt64(&a.ctime))
 	return stat, nil
 }
 
 // SetStat implements Inode.SetStat.
 func (a *InodeAttrs) SetStat(ctx context.Context, fs *vfs.Filesystem, creds *auth.Credentials, opts vfs.SetStatOptions) error {
-	return a.SetInodeStat(ctx, fs, creds, opts)
-}
-
-// SetInodeStat sets the corresponding attributes from opts to InodeAttrs.
-// This function can be used by other kernfs-based filesystem implementation to
-// sets the unexported attributes into InodeAttrs.
-func (a *InodeAttrs) SetInodeStat(ctx context.Context, fs *vfs.Filesystem, creds *auth.Credentials, opts vfs.SetStatOptions) error {
 	if opts.Stat.Mask == 0 {
 		return nil
 	}
@@ -256,9 +284,7 @@ func (a *InodeAttrs) SetInodeStat(ctx context.Context, fs *vfs.Filesystem, creds
 	// inode numbers are immutable after node creation. Setting the size is often
 	// allowed by kernfs files but does not do anything. If some other behavior is
 	// needed, the embedder should consider extending SetStat.
-	//
-	// TODO(gvisor.dev/issue/1193): Implement other stat fields like timestamps.
-	if opts.Stat.Mask&^(linux.STATX_MODE|linux.STATX_UID|linux.STATX_GID|linux.STATX_SIZE) != 0 {
+	if opts.Stat.Mask&^(linux.STATX_MODE|linux.STATX_UID|linux.STATX_GID|linux.STATX_ATIME|linux.STATX_MTIME|linux.STATX_SIZE) != 0 {
 		return syserror.EPERM
 	}
 	if opts.Stat.Mask&linux.STATX_SIZE != 0 && a.Mode().IsDir() {
@@ -286,6 +312,20 @@ func (a *InodeAttrs) SetInodeStat(ctx context.Context, fs *vfs.Filesystem, creds
 		atomic.StoreUint32(&a.gid, stat.GID)
 	}
 
+	now := ktime.NowFromContext(ctx).Nanoseconds()
+	if stat.Mask&linux.STATX_ATIME != 0 {
+		if stat.Atime.Nsec == linux.UTIME_NOW {
+			stat.Atime = linux.NsecToStatxTimestamp(now)
+		}
+		atomic.StoreInt64(&a.atime, stat.Atime.ToNsec())
+	}
+	if stat.Mask&linux.STATX_MTIME != 0 {
+		if stat.Mtime.Nsec == linux.UTIME_NOW {
+			stat.Mtime = linux.NsecToStatxTimestamp(now)
+		}
+		atomic.StoreInt64(&a.mtime, stat.Mtime.ToNsec())
+	}
+
 	return nil
 }
 
@@ -421,7 +461,7 @@ func (o *OrderedChildren) Lookup(ctx context.Context, name string) (Inode, error
 }
 
 // IterDirents implements Inode.IterDirents.
-func (o *OrderedChildren) IterDirents(ctx context.Context, cb vfs.IterDirentsCallback, offset, relOffset int64) (newOffset int64, err error) {
+func (o *OrderedChildren) IterDirents(ctx context.Context, mnt *vfs.Mount, cb vfs.IterDirentsCallback, offset, relOffset int64) (newOffset int64, err error) {
 	// All entries from OrderedChildren have already been handled in
 	// GenericDirectoryFD.IterDirents.
 	return offset, nil
@@ -619,9 +659,9 @@ type StaticDirectory struct {
 var _ Inode = (*StaticDirectory)(nil)
 
 // NewStaticDir creates a new static directory and returns its dentry.
-func NewStaticDir(creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, perm linux.FileMode, children map[string]Inode, fdOpts GenericDirectoryFDOptions) Inode {
+func NewStaticDir(ctx context.Context, creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, perm linux.FileMode, children map[string]Inode, fdOpts GenericDirectoryFDOptions) Inode {
 	inode := &StaticDirectory{}
-	inode.Init(creds, devMajor, devMinor, ino, perm, fdOpts)
+	inode.Init(ctx, creds, devMajor, devMinor, ino, perm, fdOpts)
 	inode.EnableLeakCheck()
 
 	inode.OrderedChildren.Init(OrderedChildrenOptions{})
@@ -632,12 +672,12 @@ func NewStaticDir(creds *auth.Credentials, devMajor, devMinor uint32, ino uint64
 }
 
 // Init initializes StaticDirectory.
-func (s *StaticDirectory) Init(creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, perm linux.FileMode, fdOpts GenericDirectoryFDOptions) {
+func (s *StaticDirectory) Init(ctx context.Context, creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, perm linux.FileMode, fdOpts GenericDirectoryFDOptions) {
 	if perm&^linux.PermissionsMask != 0 {
 		panic(fmt.Sprintf("Only permission mask must be set: %x", perm&linux.PermissionsMask))
 	}
 	s.fdOpts = fdOpts
-	s.InodeAttrs.Init(creds, devMajor, devMinor, ino, linux.ModeDirectory|perm)
+	s.InodeAttrs.Init(ctx, creds, devMajor, devMinor, ino, linux.ModeDirectory|perm)
 }
 
 // Open implements Inode.Open.
diff --git a/pkg/sentry/fsimpl/kernfs/kernfs.go b/pkg/sentry/fsimpl/kernfs/kernfs.go
index 606081e68..25184dbf9 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs.go
@@ -267,7 +267,9 @@ func (d *Dentry) OnZeroWatches(context.Context) {}
 // this dentry. This does not update the directory inode, so calling this on its
 // own isn't sufficient to insert a child into a directory.
 //
-// Precondition: d must represent a directory inode.
+// Preconditions:
+// * d must represent a directory inode.
+// * d.fs.mu must be locked for at least reading.
 func (d *Dentry) insertChild(name string, child *Dentry) {
 	d.dirMu.Lock()
 	d.insertChildLocked(name, child)
@@ -280,6 +282,7 @@ func (d *Dentry) insertChild(name string, child *Dentry) {
 // Preconditions:
 // * d must represent a directory inode.
 // * d.dirMu must be locked.
+// * d.fs.mu must be locked for at least reading.
 func (d *Dentry) insertChildLocked(name string, child *Dentry) {
 	if !d.isDir() {
 		panic(fmt.Sprintf("insertChildLocked called on non-directory Dentry: %+v.", d))
@@ -436,7 +439,7 @@ type inodeDirectory interface {
 	// the inode is a directory.
 	//
 	// The child returned by Lookup will be hashed into the VFS dentry tree,
-	// atleast for the duration of the current FS operation.
+	// at least for the duration of the current FS operation.
 	//
 	// Lookup must return the child with an extra reference whose ownership is
 	// transferred to the dentry that is created to point to that inode. If
@@ -454,7 +457,7 @@ type inodeDirectory interface {
 	// inside the entries returned by this IterDirents invocation. In other words,
 	// 'offset' should be used to calculate each vfs.Dirent.NextOff as well as
 	// the return value, while 'relOffset' is the place to start iteration.
-	IterDirents(ctx context.Context, callback vfs.IterDirentsCallback, offset, relOffset int64) (newOffset int64, err error)
+	IterDirents(ctx context.Context, mnt *vfs.Mount, callback vfs.IterDirentsCallback, offset, relOffset int64) (newOffset int64, err error)
 }
 
 type inodeSymlink interface {
diff --git a/pkg/sentry/fsimpl/kernfs/kernfs_test.go b/pkg/sentry/fsimpl/kernfs/kernfs_test.go
index 82fa19c03..2418eec44 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs_test.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs_test.go
@@ -36,7 +36,7 @@ const staticFileContent = "This is sample content for a static test file."
 
 // RootDentryFn is a generator function for creating the root dentry of a test
 // filesystem. See newTestSystem.
-type RootDentryFn func(*auth.Credentials, *filesystem) kernfs.Inode
+type RootDentryFn func(context.Context, *auth.Credentials, *filesystem) kernfs.Inode
 
 // newTestSystem sets up a minimal environment for running a test, including an
 // instance of a test filesystem. Tests can control the contents of the
@@ -72,10 +72,10 @@ type file struct {
 	content string
 }
 
-func (fs *filesystem) newFile(creds *auth.Credentials, content string) kernfs.Inode {
+func (fs *filesystem) newFile(ctx context.Context, creds *auth.Credentials, content string) kernfs.Inode {
 	f := &file{}
 	f.content = content
-	f.DynamicBytesFile.Init(creds, 0 /* devMajor */, 0 /* devMinor */, fs.NextIno(), f, 0777)
+	f.DynamicBytesFile.Init(ctx, creds, 0 /* devMajor */, 0 /* devMinor */, fs.NextIno(), f, 0777)
 	return f
 }
 
@@ -105,9 +105,9 @@ type readonlyDir struct {
 	locks vfs.FileLocks
 }
 
-func (fs *filesystem) newReadonlyDir(creds *auth.Credentials, mode linux.FileMode, contents map[string]kernfs.Inode) kernfs.Inode {
+func (fs *filesystem) newReadonlyDir(ctx context.Context, creds *auth.Credentials, mode linux.FileMode, contents map[string]kernfs.Inode) kernfs.Inode {
 	dir := &readonlyDir{}
-	dir.attrs.Init(creds, 0 /* devMajor */, 0 /* devMinor */, fs.NextIno(), linux.ModeDirectory|mode)
+	dir.attrs.Init(ctx, creds, 0 /* devMajor */, 0 /* devMinor */, fs.NextIno(), linux.ModeDirectory|mode)
 	dir.OrderedChildren.Init(kernfs.OrderedChildrenOptions{})
 	dir.EnableLeakCheck()
 	dir.IncLinks(dir.OrderedChildren.Populate(contents))
@@ -142,10 +142,10 @@ type dir struct {
 	fs *filesystem
 }
 
-func (fs *filesystem) newDir(creds *auth.Credentials, mode linux.FileMode, contents map[string]kernfs.Inode) kernfs.Inode {
+func (fs *filesystem) newDir(ctx context.Context, creds *auth.Credentials, mode linux.FileMode, contents map[string]kernfs.Inode) kernfs.Inode {
 	dir := &dir{}
 	dir.fs = fs
-	dir.attrs.Init(creds, 0 /* devMajor */, 0 /* devMinor */, fs.NextIno(), linux.ModeDirectory|mode)
+	dir.attrs.Init(ctx, creds, 0 /* devMajor */, 0 /* devMinor */, fs.NextIno(), linux.ModeDirectory|mode)
 	dir.OrderedChildren.Init(kernfs.OrderedChildrenOptions{Writable: true})
 	dir.EnableLeakCheck()
 
@@ -169,22 +169,24 @@ func (d *dir) DecRef(ctx context.Context) {
 
 func (d *dir) NewDir(ctx context.Context, name string, opts vfs.MkdirOptions) (kernfs.Inode, error) {
 	creds := auth.CredentialsFromContext(ctx)
-	dir := d.fs.newDir(creds, opts.Mode, nil)
+	dir := d.fs.newDir(ctx, creds, opts.Mode, nil)
 	if err := d.OrderedChildren.Insert(name, dir); err != nil {
 		dir.DecRef(ctx)
 		return nil, err
 	}
+	d.TouchCMtime(ctx)
 	d.IncLinks(1)
 	return dir, nil
 }
 
 func (d *dir) NewFile(ctx context.Context, name string, opts vfs.OpenOptions) (kernfs.Inode, error) {
 	creds := auth.CredentialsFromContext(ctx)
-	f := d.fs.newFile(creds, "")
+	f := d.fs.newFile(ctx, creds, "")
 	if err := d.OrderedChildren.Insert(name, f); err != nil {
 		f.DecRef(ctx)
 		return nil, err
 	}
+	d.TouchCMtime(ctx)
 	return f, nil
 }
 
@@ -209,7 +211,7 @@ func (fsType) Release(ctx context.Context) {}
 func (fst fsType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opt vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
 	fs := &filesystem{}
 	fs.VFSFilesystem().Init(vfsObj, &fst, fs)
-	root := fst.rootFn(creds, fs)
+	root := fst.rootFn(ctx, creds, fs)
 	var d kernfs.Dentry
 	d.Init(&fs.Filesystem, root)
 	return fs.VFSFilesystem(), d.VFSDentry(), nil
@@ -218,9 +220,9 @@ func (fst fsType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesyst
 // -------------------- Remainder of the file are test cases --------------------
 
 func TestBasic(t *testing.T) {
-	sys := newTestSystem(t, func(creds *auth.Credentials, fs *filesystem) kernfs.Inode {
-		return fs.newReadonlyDir(creds, 0755, map[string]kernfs.Inode{
-			"file1": fs.newFile(creds, staticFileContent),
+	sys := newTestSystem(t, func(ctx context.Context, creds *auth.Credentials, fs *filesystem) kernfs.Inode {
+		return fs.newReadonlyDir(ctx, creds, 0755, map[string]kernfs.Inode{
+			"file1": fs.newFile(ctx, creds, staticFileContent),
 		})
 	})
 	defer sys.Destroy()
@@ -228,9 +230,9 @@ func TestBasic(t *testing.T) {
 }
 
 func TestMkdirGetDentry(t *testing.T) {
-	sys := newTestSystem(t, func(creds *auth.Credentials, fs *filesystem) kernfs.Inode {
-		return fs.newReadonlyDir(creds, 0755, map[string]kernfs.Inode{
-			"dir1": fs.newDir(creds, 0755, nil),
+	sys := newTestSystem(t, func(ctx context.Context, creds *auth.Credentials, fs *filesystem) kernfs.Inode {
+		return fs.newReadonlyDir(ctx, creds, 0755, map[string]kernfs.Inode{
+			"dir1": fs.newDir(ctx, creds, 0755, nil),
 		})
 	})
 	defer sys.Destroy()
@@ -243,9 +245,9 @@ func TestMkdirGetDentry(t *testing.T) {
 }
 
 func TestReadStaticFile(t *testing.T) {
-	sys := newTestSystem(t, func(creds *auth.Credentials, fs *filesystem) kernfs.Inode {
-		return fs.newReadonlyDir(creds, 0755, map[string]kernfs.Inode{
-			"file1": fs.newFile(creds, staticFileContent),
+	sys := newTestSystem(t, func(ctx context.Context, creds *auth.Credentials, fs *filesystem) kernfs.Inode {
+		return fs.newReadonlyDir(ctx, creds, 0755, map[string]kernfs.Inode{
+			"file1": fs.newFile(ctx, creds, staticFileContent),
 		})
 	})
 	defer sys.Destroy()
@@ -269,9 +271,9 @@ func TestReadStaticFile(t *testing.T) {
 }
 
 func TestCreateNewFileInStaticDir(t *testing.T) {
-	sys := newTestSystem(t, func(creds *auth.Credentials, fs *filesystem) kernfs.Inode {
-		return fs.newReadonlyDir(creds, 0755, map[string]kernfs.Inode{
-			"dir1": fs.newDir(creds, 0755, nil),
+	sys := newTestSystem(t, func(ctx context.Context, creds *auth.Credentials, fs *filesystem) kernfs.Inode {
+		return fs.newReadonlyDir(ctx, creds, 0755, map[string]kernfs.Inode{
+			"dir1": fs.newDir(ctx, creds, 0755, nil),
 		})
 	})
 	defer sys.Destroy()
@@ -296,8 +298,8 @@ func TestCreateNewFileInStaticDir(t *testing.T) {
 }
 
 func TestDirFDReadWrite(t *testing.T) {
-	sys := newTestSystem(t, func(creds *auth.Credentials, fs *filesystem) kernfs.Inode {
-		return fs.newReadonlyDir(creds, 0755, nil)
+	sys := newTestSystem(t, func(ctx context.Context, creds *auth.Credentials, fs *filesystem) kernfs.Inode {
+		return fs.newReadonlyDir(ctx, creds, 0755, nil)
 	})
 	defer sys.Destroy()
 
@@ -320,14 +322,14 @@ func TestDirFDReadWrite(t *testing.T) {
 }
 
 func TestDirFDIterDirents(t *testing.T) {
-	sys := newTestSystem(t, func(creds *auth.Credentials, fs *filesystem) kernfs.Inode {
-		return fs.newReadonlyDir(creds, 0755, map[string]kernfs.Inode{
+	sys := newTestSystem(t, func(ctx context.Context, creds *auth.Credentials, fs *filesystem) kernfs.Inode {
+		return fs.newReadonlyDir(ctx, creds, 0755, map[string]kernfs.Inode{
 			// Fill root with nodes backed by various inode implementations.
-			"dir1": fs.newReadonlyDir(creds, 0755, nil),
-			"dir2": fs.newDir(creds, 0755, map[string]kernfs.Inode{
-				"dir3": fs.newDir(creds, 0755, nil),
+			"dir1": fs.newReadonlyDir(ctx, creds, 0755, nil),
+			"dir2": fs.newDir(ctx, creds, 0755, map[string]kernfs.Inode{
+				"dir3": fs.newDir(ctx, creds, 0755, nil),
 			}),
-			"file1": fs.newFile(creds, staticFileContent),
+			"file1": fs.newFile(ctx, creds, staticFileContent),
 		})
 	})
 	defer sys.Destroy()
diff --git a/pkg/sentry/fsimpl/kernfs/symlink.go b/pkg/sentry/fsimpl/kernfs/symlink.go
index 934cc6c9e..a0736c0d6 100644
--- a/pkg/sentry/fsimpl/kernfs/symlink.go
+++ b/pkg/sentry/fsimpl/kernfs/symlink.go
@@ -38,16 +38,16 @@ type StaticSymlink struct {
 var _ Inode = (*StaticSymlink)(nil)
 
 // NewStaticSymlink creates a new symlink file pointing to 'target'.
-func NewStaticSymlink(creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, target string) Inode {
+func NewStaticSymlink(ctx context.Context, creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, target string) Inode {
 	inode := &StaticSymlink{}
-	inode.Init(creds, devMajor, devMinor, ino, target)
+	inode.Init(ctx, creds, devMajor, devMinor, ino, target)
 	return inode
 }
 
 // Init initializes the instance.
-func (s *StaticSymlink) Init(creds *auth.Credentials, devMajor uint32, devMinor uint32, ino uint64, target string) {
+func (s *StaticSymlink) Init(ctx context.Context, creds *auth.Credentials, devMajor uint32, devMinor uint32, ino uint64, target string) {
 	s.target = target
-	s.InodeAttrs.Init(creds, devMajor, devMinor, ino, linux.ModeSymlink|0777)
+	s.InodeAttrs.Init(ctx, creds, devMajor, devMinor, ino, linux.ModeSymlink|0777)
 }
 
 // Readlink implements Inode.Readlink.
diff --git a/pkg/sentry/fsimpl/kernfs/synthetic_directory.go b/pkg/sentry/fsimpl/kernfs/synthetic_directory.go
index d0ed17b18..463d77d79 100644
--- a/pkg/sentry/fsimpl/kernfs/synthetic_directory.go
+++ b/pkg/sentry/fsimpl/kernfs/synthetic_directory.go
@@ -41,17 +41,17 @@ type syntheticDirectory struct {
 
 var _ Inode = (*syntheticDirectory)(nil)
 
-func newSyntheticDirectory(creds *auth.Credentials, perm linux.FileMode) Inode {
+func newSyntheticDirectory(ctx context.Context, creds *auth.Credentials, perm linux.FileMode) Inode {
 	inode := &syntheticDirectory{}
-	inode.Init(creds, 0 /* devMajor */, 0 /* devMinor */, 0 /* ino */, perm)
+	inode.Init(ctx, creds, 0 /* devMajor */, 0 /* devMinor */, 0 /* ino */, perm)
 	return inode
 }
 
-func (dir *syntheticDirectory) Init(creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, perm linux.FileMode) {
+func (dir *syntheticDirectory) Init(ctx context.Context, creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, perm linux.FileMode) {
 	if perm&^linux.PermissionsMask != 0 {
 		panic(fmt.Sprintf("perm contains non-permission bits: %#o", perm))
 	}
-	dir.InodeAttrs.Init(creds, devMajor, devMinor, ino, linux.S_IFDIR|perm)
+	dir.InodeAttrs.Init(ctx, creds, devMajor, devMinor, ino, linux.S_IFDIR|perm)
 	dir.OrderedChildren.Init(OrderedChildrenOptions{
 		Writable: true,
 	})
@@ -76,11 +76,12 @@ func (dir *syntheticDirectory) NewDir(ctx context.Context, name string, opts vfs
 	if !opts.ForSyntheticMountpoint {
 		return nil, syserror.EPERM
 	}
-	subdirI := newSyntheticDirectory(auth.CredentialsFromContext(ctx), opts.Mode&linux.PermissionsMask)
+	subdirI := newSyntheticDirectory(ctx, auth.CredentialsFromContext(ctx), opts.Mode&linux.PermissionsMask)
 	if err := dir.OrderedChildren.Insert(name, subdirI); err != nil {
 		subdirI.DecRef(ctx)
 		return nil, err
 	}
+	dir.TouchCMtime(ctx)
 	return subdirI, nil
 }