Add timestamps to VFS2 tmpfs, and implement some of SetStat.

PiperOrigin-RevId: 289962040

6 files changed, 425 insertions, 39 deletions

diff --git a/pkg/abi/linux/time.go b/pkg/abi/linux/time.go
index 546668bca..5c5a58cd4 100644
--- a/pkg/abi/linux/time.go
+++ b/pkg/abi/linux/time.go
@@ -234,6 +234,19 @@ type StatxTimestamp struct {
 	_    int32
 }
 
+// ToNsec returns the nanosecond representation.
+func (sxts StatxTimestamp) ToNsec() int64 {
+	return int64(sxts.Sec)*1e9 + int64(sxts.Nsec)
+}
+
+// ToNsecCapped returns the safe nanosecond representation.
+func (sxts StatxTimestamp) ToNsecCapped() int64 {
+	if sxts.Sec > maxSecInDuration {
+		return math.MaxInt64
+	}
+	return sxts.ToNsec()
+}
+
 // NsecToStatxTimestamp translates nanoseconds to StatxTimestamp.
 func NsecToStatxTimestamp(nsec int64) (ts StatxTimestamp) {
 	return StatxTimestamp{
diff --git a/pkg/sentry/fsimpl/tmpfs/BUILD b/pkg/sentry/fsimpl/tmpfs/BUILD
index 82f5c2f41..7601c7c04 100644
--- a/pkg/sentry/fsimpl/tmpfs/BUILD
+++ b/pkg/sentry/fsimpl/tmpfs/BUILD
@@ -40,6 +40,7 @@ go_library(
         "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/kernel/pipe",
+        "//pkg/sentry/kernel/time",
         "//pkg/sentry/memmap",
         "//pkg/sentry/pgalloc",
         "//pkg/sentry/platform",
@@ -77,6 +78,7 @@ go_test(
     srcs = [
         "pipe_test.go",
         "regular_file_test.go",
+        "stat_test.go",
     ],
     embed = [":tmpfs"],
     deps = [
diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go
index 26979729e..4cd7e9aea 100644
--- a/pkg/sentry/fsimpl/tmpfs/filesystem.go
+++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go
@@ -56,7 +56,8 @@ afterSymlink:
 	}
 	next := nextVFSD.Impl().(*dentry)
 	if symlink, ok := next.inode.impl.(*symlink); ok && rp.ShouldFollowSymlink() {
-		// TODO: symlink traversals update access time
+		// TODO(gvisor.dev/issues/1197): Symlink traversals updates
+		// access time.
 		if err := rp.HandleSymlink(symlink.target); err != nil {
 			return nil, err
 		}
@@ -501,7 +502,8 @@ func (fs *filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa
 		oldParent.inode.decLinksLocked()
 		newParent.inode.incLinksLocked()
 	}
-	// TODO: update timestamps and parent directory sizes
+	// TODO(gvisor.dev/issues/1197): Update timestamps and parent directory
+	// sizes.
 	vfsObj.CommitRenameReplaceDentry(renamedVFSD, &newParent.vfsd, newName, replacedVFSD)
 	return nil
 }
@@ -555,15 +557,11 @@ func (fs *filesystem) RmdirAt(ctx context.Context, rp *vfs.ResolvingPath) error
 func (fs *filesystem) SetStatAt(ctx context.Context, rp *vfs.ResolvingPath, opts vfs.SetStatOptions) error {
 	fs.mu.RLock()
 	defer fs.mu.RUnlock()
-	_, err := resolveLocked(rp)
+	d, err := resolveLocked(rp)
 	if err != nil {
 		return err
 	}
-	if opts.Stat.Mask == 0 {
-		return nil
-	}
-	// TODO: implement inode.setStat
-	return syserror.EPERM
+	return d.inode.setStat(opts.Stat)
 }
 
 // StatAt implements vfs.FilesystemImpl.StatAt.
@@ -587,7 +585,7 @@ func (fs *filesystem) StatFSAt(ctx context.Context, rp *vfs.ResolvingPath) (linu
 	if err != nil {
 		return linux.Statfs{}, err
 	}
-	// TODO: actually implement statfs
+	// TODO(gvisor.dev/issues/1197): Actually implement statfs.
 	return linux.Statfs{}, syserror.ENOSYS
 }
 
diff --git a/pkg/sentry/fsimpl/tmpfs/regular_file_test.go b/pkg/sentry/fsimpl/tmpfs/regular_file_test.go
index 3731c5b6f..7b0a962f0 100644
--- a/pkg/sentry/fsimpl/tmpfs/regular_file_test.go
+++ b/pkg/sentry/fsimpl/tmpfs/regular_file_test.go
@@ -18,6 +18,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"sync/atomic"
 	"testing"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -29,10 +30,12 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 )
 
-// newFileFD creates a new file in a new tmpfs mount, and returns the FD. If
-// the returned err is not nil, then cleanup should be called when the FD is no
-// longer needed.
-func newFileFD(ctx context.Context, filename string) (*vfs.FileDescription, func(), error) {
+// nextFileID is used to generate unique file names.
+var nextFileID int64
+
+// newTmpfsRoot creates a new tmpfs mount, and returns the root. If the error
+// is not nil, then cleanup should be called when the root is no longer needed.
+func newTmpfsRoot(ctx context.Context) (*vfs.VirtualFilesystem, vfs.VirtualDentry, func(), error) {
 	creds := auth.CredentialsFromContext(ctx)
 
 	vfsObj := vfs.New()
@@ -41,36 +44,124 @@ func newFileFD(ctx context.Context, filename string) (*vfs.FileDescription, func
 	})
 	mntns, err := vfsObj.NewMountNamespace(ctx, creds, "", "tmpfs", &vfs.GetFilesystemOptions{})
 	if err != nil {
-		return nil, nil, fmt.Errorf("failed to create tmpfs root mount: %v", err)
+		return nil, vfs.VirtualDentry{}, nil, fmt.Errorf("failed to create tmpfs root mount: %v", err)
 	}
 	root := mntns.Root()
+	return vfsObj, root, func() {
+		root.DecRef()
+		mntns.DecRef(vfsObj)
+	}, nil
+}
+
+// newFileFD creates a new file in a new tmpfs mount, and returns the FD. If
+// the returned err is not nil, then cleanup should be called when the FD is no
+// longer needed.
+func newFileFD(ctx context.Context, mode linux.FileMode) (*vfs.FileDescription, func(), error) {
+	creds := auth.CredentialsFromContext(ctx)
+	vfsObj, root, cleanup, err := newTmpfsRoot(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	filename := fmt.Sprintf("tmpfs-test-file-%d", atomic.AddInt64(&nextFileID, 1))
 
 	// Create the file that will be write/read.
 	fd, err := vfsObj.OpenAt(ctx, creds, &vfs.PathOperation{
-		Root:               root,
-		Start:              root,
-		Path:               fspath.Parse(filename),
-		FollowFinalSymlink: true,
+		Root:  root,
+		Start: root,
+		Path:  fspath.Parse(filename),
 	}, &vfs.OpenOptions{
 		Flags: linux.O_RDWR | linux.O_CREAT | linux.O_EXCL,
-		Mode:  0644,
+		Mode:  linux.ModeRegular | mode,
 	})
 	if err != nil {
-		root.DecRef()
-		mntns.DecRef(vfsObj)
+		cleanup()
 		return nil, nil, fmt.Errorf("failed to create file %q: %v", filename, err)
 	}
 
-	return fd, func() {
-		root.DecRef()
-		mntns.DecRef(vfsObj)
-	}, nil
+	return fd, cleanup, nil
+}
+
+// newDirFD is like newFileFD, but for directories.
+func newDirFD(ctx context.Context, mode linux.FileMode) (*vfs.FileDescription, func(), error) {
+	creds := auth.CredentialsFromContext(ctx)
+	vfsObj, root, cleanup, err := newTmpfsRoot(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	dirname := fmt.Sprintf("tmpfs-test-dir-%d", atomic.AddInt64(&nextFileID, 1))
+
+	// Create the dir.
+	if err := vfsObj.MkdirAt(ctx, creds, &vfs.PathOperation{
+		Root:  root,
+		Start: root,
+		Path:  fspath.Parse(dirname),
+	}, &vfs.MkdirOptions{
+		Mode: linux.ModeDirectory | mode,
+	}); err != nil {
+		cleanup()
+		return nil, nil, fmt.Errorf("failed to create directory %q: %v", dirname, err)
+	}
+
+	// Open the dir and return it.
+	fd, err := vfsObj.OpenAt(ctx, creds, &vfs.PathOperation{
+		Root:  root,
+		Start: root,
+		Path:  fspath.Parse(dirname),
+	}, &vfs.OpenOptions{
+		Flags: linux.O_RDONLY | linux.O_DIRECTORY,
+	})
+	if err != nil {
+		cleanup()
+		return nil, nil, fmt.Errorf("failed to open directory %q: %v", dirname, err)
+	}
+
+	return fd, cleanup, nil
+}
+
+// newPipeFD is like newFileFD, but for pipes.
+func newPipeFD(ctx context.Context, mode linux.FileMode) (*vfs.FileDescription, func(), error) {
+	creds := auth.CredentialsFromContext(ctx)
+	vfsObj, root, cleanup, err := newTmpfsRoot(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	pipename := fmt.Sprintf("tmpfs-test-pipe-%d", atomic.AddInt64(&nextFileID, 1))
+
+	// Create the pipe.
+	if err := vfsObj.MknodAt(ctx, creds, &vfs.PathOperation{
+		Root:  root,
+		Start: root,
+		Path:  fspath.Parse(pipename),
+	}, &vfs.MknodOptions{
+		Mode: linux.ModeNamedPipe | mode,
+	}); err != nil {
+		cleanup()
+		return nil, nil, fmt.Errorf("failed to create pipe %q: %v", pipename, err)
+	}
+
+	// Open the pipe and return it.
+	fd, err := vfsObj.OpenAt(ctx, creds, &vfs.PathOperation{
+		Root:  root,
+		Start: root,
+		Path:  fspath.Parse(pipename),
+	}, &vfs.OpenOptions{
+		Flags: linux.O_RDWR,
+	})
+	if err != nil {
+		cleanup()
+		return nil, nil, fmt.Errorf("failed to open pipe %q: %v", pipename, err)
+	}
+
+	return fd, cleanup, nil
 }
 
 // Test that we can write some data to a file and read it back.`
 func TestSimpleWriteRead(t *testing.T) {
 	ctx := contexttest.Context(t)
-	fd, cleanup, err := newFileFD(ctx, "simpleReadWrite")
+	fd, cleanup, err := newFileFD(ctx, 0644)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -116,7 +207,7 @@ func TestSimpleWriteRead(t *testing.T) {
 
 func TestPWrite(t *testing.T) {
 	ctx := contexttest.Context(t)
-	fd, cleanup, err := newFileFD(ctx, "PRead")
+	fd, cleanup, err := newFileFD(ctx, 0644)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -171,7 +262,7 @@ func TestPWrite(t *testing.T) {
 
 func TestPRead(t *testing.T) {
 	ctx := contexttest.Context(t)
-	fd, cleanup, err := newFileFD(ctx, "PRead")
+	fd, cleanup, err := newFileFD(ctx, 0644)
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/pkg/sentry/fsimpl/tmpfs/stat_test.go b/pkg/sentry/fsimpl/tmpfs/stat_test.go
new file mode 100644
index 000000000..ebe035dee
--- /dev/null
+++ b/pkg/sentry/fsimpl/tmpfs/stat_test.go
@@ -0,0 +1,232 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tmpfs
+
+import (
+	"fmt"
+	"testing"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/contexttest"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+)
+
+func TestStatAfterCreate(t *testing.T) {
+	ctx := contexttest.Context(t)
+	mode := linux.FileMode(0644)
+
+	// Run with different file types.
+	// TODO(gvisor.dev/issues/1197): Also test symlinks and sockets.
+	for _, typ := range []string{"file", "dir", "pipe"} {
+		t.Run(fmt.Sprintf("type=%q", typ), func(t *testing.T) {
+			var (
+				fd      *vfs.FileDescription
+				cleanup func()
+				err     error
+			)
+			switch typ {
+			case "file":
+				fd, cleanup, err = newFileFD(ctx, mode)
+			case "dir":
+				fd, cleanup, err = newDirFD(ctx, mode)
+			case "pipe":
+				fd, cleanup, err = newPipeFD(ctx, mode)
+			default:
+				panic(fmt.Sprintf("unknown typ %q", typ))
+			}
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer cleanup()
+
+			got, err := fd.Stat(ctx, vfs.StatOptions{})
+			if err != nil {
+				t.Fatalf("Stat failed: %v", err)
+			}
+
+			// Atime, Ctime, Mtime should all be current time (non-zero).
+			atime, ctime, mtime := got.Atime.ToNsec(), got.Ctime.ToNsec(), got.Mtime.ToNsec()
+			if atime != ctime || ctime != mtime {
+				t.Errorf("got atime=%d ctime=%d mtime=%d, wanted equal values", atime, ctime, mtime)
+			}
+			if atime == 0 {
+				t.Errorf("got atime=%d, want non-zero", atime)
+			}
+
+			// Btime should be 0, as it is not set by tmpfs.
+			if btime := got.Btime.ToNsec(); btime != 0 {
+				t.Errorf("got btime %d, want 0", got.Btime.ToNsec())
+			}
+
+			// Size should be 0.
+			if got.Size != 0 {
+				t.Errorf("got size %d, want 0", got.Size)
+			}
+
+			// Nlink should be 1 for files, 2 for dirs.
+			wantNlink := uint32(1)
+			if typ == "dir" {
+				wantNlink = 2
+			}
+			if got.Nlink != wantNlink {
+				t.Errorf("got nlink %d, want %d", got.Nlink, wantNlink)
+			}
+
+			// UID and GID are set from context creds.
+			creds := auth.CredentialsFromContext(ctx)
+			if got.UID != uint32(creds.EffectiveKUID) {
+				t.Errorf("got uid %d, want %d", got.UID, uint32(creds.EffectiveKUID))
+			}
+			if got.GID != uint32(creds.EffectiveKGID) {
+				t.Errorf("got gid %d, want %d", got.GID, uint32(creds.EffectiveKGID))
+			}
+
+			// Mode.
+			wantMode := uint16(mode)
+			switch typ {
+			case "file":
+				wantMode |= linux.S_IFREG
+			case "dir":
+				wantMode |= linux.S_IFDIR
+			case "pipe":
+				wantMode |= linux.S_IFIFO
+			default:
+				panic(fmt.Sprintf("unknown typ %q", typ))
+			}
+
+			if got.Mode != wantMode {
+				t.Errorf("got mode %x, want %x", got.Mode, wantMode)
+			}
+
+			// Ino.
+			if got.Ino == 0 {
+				t.Errorf("got ino %d, want not 0", got.Ino)
+			}
+		})
+	}
+}
+
+func TestSetStatAtime(t *testing.T) {
+	ctx := contexttest.Context(t)
+	fd, cleanup, err := newFileFD(ctx, 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer cleanup()
+
+	allStatOptions := vfs.StatOptions{Mask: linux.STATX_ALL}
+
+	// Get initial stat.
+	initialStat, err := fd.Stat(ctx, allStatOptions)
+	if err != nil {
+		t.Fatalf("Stat failed: %v", err)
+	}
+
+	// Set atime, but without the mask.
+	if err := fd.SetStat(ctx, vfs.SetStatOptions{Stat: linux.Statx{
+		Mask:  0,
+		Atime: linux.NsecToStatxTimestamp(100),
+	}}); err != nil {
+		t.Errorf("SetStat atime without mask failed: %v")
+	}
+	// Atime should be unchanged.
+	if gotStat, err := fd.Stat(ctx, allStatOptions); err != nil {
+		t.Errorf("Stat got error: %v", err)
+	} else if gotStat.Atime != initialStat.Atime {
+		t.Errorf("Stat got atime %d, want %d", gotStat.Atime, initialStat.Atime)
+	}
+
+	// Set atime, this time included in the mask.
+	setStat := linux.Statx{
+		Mask:  linux.STATX_ATIME,
+		Atime: linux.NsecToStatxTimestamp(100),
+	}
+	if err := fd.SetStat(ctx, vfs.SetStatOptions{Stat: setStat}); err != nil {
+		t.Errorf("SetStat atime with mask failed: %v")
+	}
+	if gotStat, err := fd.Stat(ctx, allStatOptions); err != nil {
+		t.Errorf("Stat got error: %v", err)
+	} else if gotStat.Atime != setStat.Atime {
+		t.Errorf("Stat got atime %d, want %d", gotStat.Atime, setStat.Atime)
+	}
+}
+
+func TestSetStat(t *testing.T) {
+	ctx := contexttest.Context(t)
+	mode := linux.FileMode(0644)
+
+	// Run with different file types.
+	// TODO(gvisor.dev/issues/1197): Also test symlinks and sockets.
+	for _, typ := range []string{"file", "dir", "pipe"} {
+		t.Run(fmt.Sprintf("type=%q", typ), func(t *testing.T) {
+			var (
+				fd      *vfs.FileDescription
+				cleanup func()
+				err     error
+			)
+			switch typ {
+			case "file":
+				fd, cleanup, err = newFileFD(ctx, mode)
+			case "dir":
+				fd, cleanup, err = newDirFD(ctx, mode)
+			case "pipe":
+				fd, cleanup, err = newPipeFD(ctx, mode)
+			default:
+				panic(fmt.Sprintf("unknown typ %q", typ))
+			}
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer cleanup()
+
+			allStatOptions := vfs.StatOptions{Mask: linux.STATX_ALL}
+
+			// Get initial stat.
+			initialStat, err := fd.Stat(ctx, allStatOptions)
+			if err != nil {
+				t.Fatalf("Stat failed: %v", err)
+			}
+
+			// Set atime, but without the mask.
+			if err := fd.SetStat(ctx, vfs.SetStatOptions{Stat: linux.Statx{
+				Mask:  0,
+				Atime: linux.NsecToStatxTimestamp(100),
+			}}); err != nil {
+				t.Errorf("SetStat atime without mask failed: %v")
+			}
+			// Atime should be unchanged.
+			if gotStat, err := fd.Stat(ctx, allStatOptions); err != nil {
+				t.Errorf("Stat got error: %v", err)
+			} else if gotStat.Atime != initialStat.Atime {
+				t.Errorf("Stat got atime %d, want %d", gotStat.Atime, initialStat.Atime)
+			}
+
+			// Set atime, this time included in the mask.
+			setStat := linux.Statx{
+				Mask:  linux.STATX_ATIME,
+				Atime: linux.NsecToStatxTimestamp(100),
+			}
+			if err := fd.SetStat(ctx, vfs.SetStatOptions{Stat: setStat}); err != nil {
+				t.Errorf("SetStat atime with mask failed: %v")
+			}
+			if gotStat, err := fd.Stat(ctx, allStatOptions); err != nil {
+				t.Errorf("Stat got error: %v", err)
+			} else if gotStat.Atime != setStat.Atime {
+				t.Errorf("Stat got atime %d, want %d", gotStat.Atime, setStat.Atime)
+			}
+		})
+	}
+}
diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
index 701826f90..d6960ee47 100644
--- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go
+++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
@@ -31,10 +31,10 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/sync"
-	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 // FilesystemType implements vfs.FilesystemType.
@@ -47,6 +47,9 @@ type filesystem struct {
 	// memFile is used to allocate pages to for regular files.
 	memFile *pgalloc.MemoryFile
 
+	// clock is a realtime clock used to set timestamps in file operations.
+	clock time.Clock
+
 	// mu serializes changes to the Dentry tree.
 	mu sync.RWMutex
 
@@ -59,8 +62,10 @@ func (fstype FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.Virt
 	if memFileProvider == nil {
 		panic("MemoryFileProviderFromContext returned nil")
 	}
+	clock := time.RealtimeClockFromContext(ctx)
 	fs := filesystem{
 		memFile: memFileProvider.MemoryFile(),
+		clock:   clock,
 	}
 	fs.vfsfs.Init(vfsObj, &fs)
 	root := fs.newDentry(fs.newDirectory(creds, 01777))
@@ -126,26 +131,36 @@ type inode struct {
 	// filesystem.RmdirAt() drops the reference.
 	refs int64
 
-	// Inode metadata; protected by mu and accessed using atomic memory
-	// operations unless otherwise specified.
-	mu    sync.RWMutex
+	// Inode metadata. Writing multiple fields atomically requires holding
+	// mu, othewise atomic operations can be used.
+	mu    sync.Mutex
 	mode  uint32 // excluding file type bits, which are based on impl
 	nlink uint32 // protected by filesystem.mu instead of inode.mu
 	uid   uint32 // auth.KUID, but stored as raw uint32 for sync/atomic
 	gid   uint32 // auth.KGID, but ...
 	ino   uint64 // immutable
 
+	// Linux's tmpfs has no concept of btime.
+	atime int64 // nanoseconds
+	ctime int64 // nanoseconds
+	mtime int64 // nanoseconds
+
 	impl interface{} // immutable
 }
 
 const maxLinks = math.MaxUint32
 
 func (i *inode) init(impl interface{}, fs *filesystem, creds *auth.Credentials, mode linux.FileMode) {
+	now := fs.clock.Now().Nanoseconds()
 	i.refs = 1
 	i.mode = uint32(mode)
 	i.uid = uint32(creds.EffectiveKUID)
 	i.gid = uint32(creds.EffectiveKGID)
 	i.ino = atomic.AddUint64(&fs.nextInoMinusOne, 1)
+	// Tmpfs creation sets atime, ctime, and mtime to current time.
+	i.atime = now
+	i.ctime = now
+	i.mtime = now
 	// i.nlink initialized by caller
 	i.impl = impl
 }
@@ -213,15 +228,24 @@ func (i *inode) checkPermissions(creds *auth.Credentials, ats vfs.AccessTypes, i
 // Go won't inline this function, and returning linux.Statx (which is quite
 // big) means spending a lot of time in runtime.duffcopy(), so instead it's an
 // output parameter.
+//
+// Note that Linux does not guarantee to return consistent data (in the case of
+// a concurrent modification), so we do not require holding inode.mu.
 func (i *inode) statTo(stat *linux.Statx) {
-	stat.Mask = linux.STATX_TYPE | linux.STATX_MODE | linux.STATX_NLINK | linux.STATX_UID | linux.STATX_GID | linux.STATX_INO
+	stat.Mask = linux.STATX_TYPE | linux.STATX_MODE | linux.STATX_NLINK |
+		linux.STATX_UID | linux.STATX_GID | linux.STATX_INO | linux.STATX_ATIME |
+		linux.STATX_BTIME | linux.STATX_CTIME | linux.STATX_MTIME
 	stat.Blksize = 1 // usermem.PageSize in tmpfs
 	stat.Nlink = atomic.LoadUint32(&i.nlink)
 	stat.UID = atomic.LoadUint32(&i.uid)
 	stat.GID = atomic.LoadUint32(&i.gid)
 	stat.Mode = uint16(atomic.LoadUint32(&i.mode))
 	stat.Ino = i.ino
-	// TODO: device number
+	// Linux's tmpfs has no concept of btime, so zero-value is returned.
+	stat.Atime = linux.NsecToStatxTimestamp(i.atime)
+	stat.Ctime = linux.NsecToStatxTimestamp(i.ctime)
+	stat.Mtime = linux.NsecToStatxTimestamp(i.mtime)
+	// TODO(gvisor.dev/issues/1197): Device number.
 	switch impl := i.impl.(type) {
 	case *regularFile:
 		stat.Mode |= linux.S_IFREG
@@ -245,6 +269,36 @@ func (i *inode) statTo(stat *linux.Statx) {
 	}
 }
 
+func (i *inode) setStat(stat linux.Statx) error {
+	// TODO(gvisor.dev/issues/1197): Handle stat.Size by growing/shrinking
+	// the file.
+	if stat.Mask == 0 {
+		return nil
+	}
+	i.mu.Lock()
+	mask := stat.Mask
+	if mask&linux.STATX_MODE != 0 {
+		atomic.StoreUint32(&i.mode, uint32(stat.Mode))
+	}
+	if mask&linux.STATX_UID != 0 {
+		atomic.StoreUint32(&i.uid, stat.UID)
+	}
+	if mask&linux.STATX_GID != 0 {
+		atomic.StoreUint32(&i.gid, stat.GID)
+	}
+	if mask&linux.STATX_ATIME != 0 {
+		atomic.StoreInt64(&i.atime, stat.Atime.ToNsecCapped())
+	}
+	if mask&linux.STATX_CTIME != 0 {
+		atomic.StoreInt64(&i.ctime, stat.Ctime.ToNsecCapped())
+	}
+	if mask&linux.STATX_MTIME != 0 {
+		atomic.StoreInt64(&i.mtime, stat.Mtime.ToNsecCapped())
+	}
+	i.mu.Unlock()
+	return nil
+}
+
 // allocatedBlocksForSize returns the number of 512B blocks needed to
 // accommodate the given size in bytes, as appropriate for struct
 // stat::st_blocks and struct statx::stx_blocks. (Note that this 512B block
@@ -291,9 +345,5 @@ func (fd *fileDescription) Stat(ctx context.Context, opts vfs.StatOptions) (linu
 
 // SetStat implements vfs.FileDescriptionImpl.SetStat.
 func (fd *fileDescription) SetStat(ctx context.Context, opts vfs.SetStatOptions) error {
-	if opts.Stat.Mask == 0 {
-		return nil
-	}
-	// TODO: implement inode.setStat
-	return syserror.EPERM
+	return fd.inode().setStat(opts.Stat)
 }