Merge branch 'master' into iptables-1-pkg

Change-Id: I7457a11de4725e1bf3811420c505d225b1cb6943

13 files changed, 162 insertions, 244 deletions

diff --git a/pkg/sentry/fs/dirent.go b/pkg/sentry/fs/dirent.go
index c0bc261a2..a0a35c242 100644
--- a/pkg/sentry/fs/dirent.go
+++ b/pkg/sentry/fs/dirent.go
@@ -805,7 +805,7 @@ func (d *Dirent) Bind(ctx context.Context, root *Dirent, name string, data trans
 	var childDir *Dirent
 	err := d.genericCreate(ctx, root, name, func() error {
 		var e error
-		childDir, e = d.Inode.Bind(ctx, name, data, perms)
+		childDir, e = d.Inode.Bind(ctx, d, name, data, perms)
 		if e != nil {
 			return e
 		}
diff --git a/pkg/sentry/fs/file.go b/pkg/sentry/fs/file.go
index 8c1307235..f64954457 100644
--- a/pkg/sentry/fs/file.go
+++ b/pkg/sentry/fs/file.go
@@ -545,12 +545,28 @@ type lockedWriter struct {
 
 // Write implements io.Writer.Write.
 func (w *lockedWriter) Write(buf []byte) (int, error) {
-	n, err := w.File.FileOperations.Write(w.Ctx, w.File, usermem.BytesIOSequence(buf), w.File.offset)
-	return int(n), err
+	return w.WriteAt(buf, w.File.offset)
 }
 
 // WriteAt implements io.Writer.WriteAt.
 func (w *lockedWriter) WriteAt(buf []byte, offset int64) (int, error) {
-	n, err := w.File.FileOperations.Write(w.Ctx, w.File, usermem.BytesIOSequence(buf), offset)
-	return int(n), err
+	var (
+		written int
+		err     error
+	)
+	// The io.Writer contract requires that Write writes all available
+	// bytes and does not return short writes. This causes errors with
+	// io.Copy, since our own Write interface does not have this same
+	// contract. Enforce that here.
+	for written < len(buf) {
+		var n int64
+		n, err = w.File.FileOperations.Write(w.Ctx, w.File, usermem.BytesIOSequence(buf[written:]), offset+int64(written))
+		if n > 0 {
+			written += int(n)
+		}
+		if err != nil {
+			break
+		}
+	}
+	return written, err
 }
diff --git a/pkg/sentry/fs/gofer/socket.go b/pkg/sentry/fs/gofer/socket.go
index cbd5b9a84..7ac0a421f 100644
--- a/pkg/sentry/fs/gofer/socket.go
+++ b/pkg/sentry/fs/gofer/socket.go
@@ -15,6 +15,7 @@
 package gofer
 
 import (
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
 	"gvisor.googlesource.com/gvisor/pkg/log"
 	"gvisor.googlesource.com/gvisor/pkg/p9"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
@@ -61,13 +62,13 @@ type endpoint struct {
 	path string
 }
 
-func unixSockToP9(t transport.SockType) (p9.ConnectFlags, bool) {
+func sockTypeToP9(t linux.SockType) (p9.ConnectFlags, bool) {
 	switch t {
-	case transport.SockStream:
+	case linux.SOCK_STREAM:
 		return p9.StreamSocket, true
-	case transport.SockSeqpacket:
+	case linux.SOCK_SEQPACKET:
 		return p9.SeqpacketSocket, true
-	case transport.SockDgram:
+	case linux.SOCK_DGRAM:
 		return p9.DgramSocket, true
 	}
 	return 0, false
@@ -75,7 +76,7 @@ func unixSockToP9(t transport.SockType) (p9.ConnectFlags, bool) {
 
 // BidirectionalConnect implements ConnectableEndpoint.BidirectionalConnect.
 func (e *endpoint) BidirectionalConnect(ce transport.ConnectingEndpoint, returnConnect func(transport.Receiver, transport.ConnectedEndpoint)) *syserr.Error {
-	cf, ok := unixSockToP9(ce.Type())
+	cf, ok := sockTypeToP9(ce.Type())
 	if !ok {
 		return syserr.ErrConnectionRefused
 	}
@@ -139,3 +140,8 @@ func (e *endpoint) UnidirectionalConnect() (transport.ConnectedEndpoint, *syserr
 func (e *endpoint) Release() {
 	e.inode.DecRef()
 }
+
+// Passcred implements transport.BoundEndpoint.Passcred.
+func (e *endpoint) Passcred() bool {
+	return false
+}
diff --git a/pkg/sentry/fs/host/socket.go b/pkg/sentry/fs/host/socket.go
index 3ed137006..305eea718 100644
--- a/pkg/sentry/fs/host/socket.go
+++ b/pkg/sentry/fs/host/socket.go
@@ -15,9 +15,11 @@
 package host
 
 import (
+	"fmt"
 	"sync"
 	"syscall"
 
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
 	"gvisor.googlesource.com/gvisor/pkg/fd"
 	"gvisor.googlesource.com/gvisor/pkg/fdnotifier"
 	"gvisor.googlesource.com/gvisor/pkg/log"
@@ -51,25 +53,11 @@ type ConnectedEndpoint struct {
 	// ref keeps track of references to a connectedEndpoint.
 	ref refs.AtomicRefCount
 
-	// mu protects fd, readClosed and writeClosed.
-	mu sync.RWMutex `state:"nosave"`
-
-	// file is an *fd.FD containing the FD backing this endpoint. It must be
-	// set to nil if it has been closed.
-	file *fd.FD `state:"nosave"`
-
-	// readClosed is true if the FD has read shutdown or if it has been closed.
-	readClosed bool
-
-	// writeClosed is true if the FD has write shutdown or if it has been
-	// closed.
-	writeClosed bool
-
 	// If srfd >= 0, it is the host FD that file was imported from.
 	srfd int `state:"wait"`
 
 	// stype is the type of Unix socket.
-	stype transport.SockType
+	stype linux.SockType
 
 	// sndbuf is the size of the send buffer.
 	//
@@ -78,6 +66,13 @@ type ConnectedEndpoint struct {
 	// prevent lots of small messages from filling the real send buffer
 	// size on the host.
 	sndbuf int `state:"nosave"`
+
+	// mu protects the fields below.
+	mu sync.RWMutex `state:"nosave"`
+
+	// file is an *fd.FD containing the FD backing this endpoint. It must be
+	// set to nil if it has been closed.
+	file *fd.FD `state:"nosave"`
 }
 
 // init performs initialization required for creating new ConnectedEndpoints and
@@ -111,7 +106,7 @@ func (c *ConnectedEndpoint) init() *syserr.Error {
 		return syserr.ErrInvalidEndpointState
 	}
 
-	c.stype = transport.SockType(stype)
+	c.stype = linux.SockType(stype)
 	c.sndbuf = sndbuf
 
 	return nil
@@ -169,7 +164,7 @@ func NewSocketWithDirent(ctx context.Context, d *fs.Dirent, f *fd.FD, flags fs.F
 
 	ep := transport.NewExternal(e.stype, uniqueid.GlobalProviderFromContext(ctx), &q, e, e)
 
-	return unixsocket.NewWithDirent(ctx, d, ep, e.stype != transport.SockStream, flags), nil
+	return unixsocket.NewWithDirent(ctx, d, ep, e.stype, flags), nil
 }
 
 // newSocket allocates a new unix socket with host endpoint.
@@ -201,16 +196,13 @@ func newSocket(ctx context.Context, orgfd int, saveable bool) (*fs.File, error)
 
 	ep := transport.NewExternal(e.stype, uniqueid.GlobalProviderFromContext(ctx), &q, e, e)
 
-	return unixsocket.New(ctx, ep, e.stype != transport.SockStream), nil
+	return unixsocket.New(ctx, ep, e.stype), nil
 }
 
 // Send implements transport.ConnectedEndpoint.Send.
 func (c *ConnectedEndpoint) Send(data [][]byte, controlMessages transport.ControlMessages, from tcpip.FullAddress) (uintptr, bool, *syserr.Error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.writeClosed {
-		return 0, false, syserr.ErrClosedForSend
-	}
 
 	if !controlMessages.Empty() {
 		return 0, false, syserr.ErrInvalidEndpointState
@@ -218,7 +210,7 @@ func (c *ConnectedEndpoint) Send(data [][]byte, controlMessages transport.Contro
 
 	// Since stream sockets don't preserve message boundaries, we can write
 	// only as much of the message as fits in the send buffer.
-	truncate := c.stype == transport.SockStream
+	truncate := c.stype == linux.SOCK_STREAM
 
 	n, totalLen, err := fdWriteVec(c.file.FD(), data, c.sndbuf, truncate)
 	if n < totalLen && err == nil {
@@ -244,8 +236,13 @@ func (c *ConnectedEndpoint) SendNotify() {}
 // CloseSend implements transport.ConnectedEndpoint.CloseSend.
 func (c *ConnectedEndpoint) CloseSend() {
 	c.mu.Lock()
-	c.writeClosed = true
-	c.mu.Unlock()
+	defer c.mu.Unlock()
+
+	if err := syscall.Shutdown(c.file.FD(), syscall.SHUT_WR); err != nil {
+		// A well-formed UDS shutdown can't fail. See
+		// net/unix/af_unix.c:unix_shutdown.
+		panic(fmt.Sprintf("failed write shutdown on host socket %+v: %v", c, err))
+	}
 }
 
 // CloseNotify implements transport.ConnectedEndpoint.CloseNotify.
@@ -255,9 +252,7 @@ func (c *ConnectedEndpoint) CloseNotify() {}
 func (c *ConnectedEndpoint) Writable() bool {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.writeClosed {
-		return true
-	}
+
 	return fdnotifier.NonBlockingPoll(int32(c.file.FD()), waiter.EventOut)&waiter.EventOut != 0
 }
 
@@ -285,9 +280,6 @@ func (c *ConnectedEndpoint) EventUpdate() {
 func (c *ConnectedEndpoint) Recv(data [][]byte, creds bool, numRights uintptr, peek bool) (uintptr, uintptr, transport.ControlMessages, bool, tcpip.FullAddress, bool, *syserr.Error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.readClosed {
-		return 0, 0, transport.ControlMessages{}, false, tcpip.FullAddress{}, false, syserr.ErrClosedForReceive
-	}
 
 	var cm unet.ControlMessage
 	if numRights > 0 {
@@ -344,31 +336,34 @@ func (c *ConnectedEndpoint) RecvNotify() {}
 // CloseRecv implements transport.Receiver.CloseRecv.
 func (c *ConnectedEndpoint) CloseRecv() {
 	c.mu.Lock()
-	c.readClosed = true
-	c.mu.Unlock()
+	defer c.mu.Unlock()
+
+	if err := syscall.Shutdown(c.file.FD(), syscall.SHUT_RD); err != nil {
+		// A well-formed UDS shutdown can't fail. See
+		// net/unix/af_unix.c:unix_shutdown.
+		panic(fmt.Sprintf("failed read shutdown on host socket %+v: %v", c, err))
+	}
 }
 
 // Readable implements transport.Receiver.Readable.
 func (c *ConnectedEndpoint) Readable() bool {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.readClosed {
-		return true
-	}
+
 	return fdnotifier.NonBlockingPoll(int32(c.file.FD()), waiter.EventIn)&waiter.EventIn != 0
 }
 
 // SendQueuedSize implements transport.Receiver.SendQueuedSize.
 func (c *ConnectedEndpoint) SendQueuedSize() int64 {
-	// SendQueuedSize isn't supported for host sockets because we don't allow the
-	// sentry to call ioctl(2).
+	// TODO(gvisor.dev/issue/273): SendQueuedSize isn't supported for host
+	// sockets because we don't allow the sentry to call ioctl(2).
 	return -1
 }
 
 // RecvQueuedSize implements transport.Receiver.RecvQueuedSize.
 func (c *ConnectedEndpoint) RecvQueuedSize() int64 {
-	// RecvQueuedSize isn't supported for host sockets because we don't allow the
-	// sentry to call ioctl(2).
+	// TODO(gvisor.dev/issue/273): RecvQueuedSize isn't supported for host
+	// sockets because we don't allow the sentry to call ioctl(2).
 	return -1
 }
 
diff --git a/pkg/sentry/fs/host/socket_test.go b/pkg/sentry/fs/host/socket_test.go
index 06392a65a..bc3ce5627 100644
--- a/pkg/sentry/fs/host/socket_test.go
+++ b/pkg/sentry/fs/host/socket_test.go
@@ -198,20 +198,6 @@ func TestListen(t *testing.T) {
 	}
 }
 
-func TestSend(t *testing.T) {
-	e := ConnectedEndpoint{writeClosed: true}
-	if _, _, err := e.Send(nil, transport.ControlMessages{}, tcpip.FullAddress{}); err != syserr.ErrClosedForSend {
-		t.Errorf("Got %#v.Send() = %v, want = %v", e, err, syserr.ErrClosedForSend)
-	}
-}
-
-func TestRecv(t *testing.T) {
-	e := ConnectedEndpoint{readClosed: true}
-	if _, _, _, _, _, _, err := e.Recv(nil, false, 0, false); err != syserr.ErrClosedForReceive {
-		t.Errorf("Got %#v.Recv() = %v, want = %v", e, err, syserr.ErrClosedForReceive)
-	}
-}
-
 func TestPasscred(t *testing.T) {
 	e := ConnectedEndpoint{}
 	if got, want := e.Passcred(), false; got != want {
@@ -244,20 +230,6 @@ func TestQueuedSize(t *testing.T) {
 	}
 }
 
-func TestReadable(t *testing.T) {
-	e := ConnectedEndpoint{readClosed: true}
-	if got, want := e.Readable(), true; got != want {
-		t.Errorf("Got %#v.Readable() = %t, want = %t", e, got, want)
-	}
-}
-
-func TestWritable(t *testing.T) {
-	e := ConnectedEndpoint{writeClosed: true}
-	if got, want := e.Writable(), true; got != want {
-		t.Errorf("Got %#v.Writable() = %t, want = %t", e, got, want)
-	}
-}
-
 func TestRelease(t *testing.T) {
 	f, err := syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
 	if err != nil {
@@ -272,131 +244,3 @@ func TestRelease(t *testing.T) {
 		t.Errorf("got = %#v, want = %#v", c, want)
 	}
 }
-
-func TestClose(t *testing.T) {
-	type testCase struct {
-		name  string
-		cep   *ConnectedEndpoint
-		addFD bool
-		f     func()
-		want  *ConnectedEndpoint
-	}
-
-	var tests []testCase
-
-	// nil is the value used by ConnectedEndpoint to indicate a closed file.
-	// Non-nil files are used to check if the file gets closed.
-
-	f, err := syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c := &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f)}
-	tests = append(tests, testCase{
-		name:  "First CloseRecv",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseRecv,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), readClosed: true}
-	tests = append(tests, testCase{
-		name:  "Second CloseRecv",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseRecv,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f)}
-	tests = append(tests, testCase{
-		name:  "First CloseSend",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseSend,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), writeClosed: true}
-	tests = append(tests, testCase{
-		name:  "Second CloseSend",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseSend,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), writeClosed: true}
-	tests = append(tests, testCase{
-		name:  "CloseSend then CloseRecv",
-		cep:   c,
-		addFD: true,
-		f:     c.CloseRecv,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), readClosed: true}
-	tests = append(tests, testCase{
-		name:  "CloseRecv then CloseSend",
-		cep:   c,
-		addFD: true,
-		f:     c.CloseSend,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), readClosed: true, writeClosed: true}
-	tests = append(tests, testCase{
-		name:  "Full close then CloseRecv",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseRecv,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), readClosed: true, writeClosed: true}
-	tests = append(tests, testCase{
-		name:  "Full close then CloseSend",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseSend,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true, writeClosed: true},
-	})
-
-	for _, test := range tests {
-		if test.addFD {
-			fdnotifier.AddFD(int32(test.cep.file.FD()), nil)
-		}
-		if test.f(); !reflect.DeepEqual(test.cep, test.want) {
-			t.Errorf("%s: got = %#v, want = %#v", test.name, test.cep, test.want)
-		}
-	}
-}
diff --git a/pkg/sentry/fs/inode.go b/pkg/sentry/fs/inode.go
index aef1a1cb9..0b54c2e77 100644
--- a/pkg/sentry/fs/inode.go
+++ b/pkg/sentry/fs/inode.go
@@ -220,9 +220,9 @@ func (i *Inode) Rename(ctx context.Context, oldParent *Dirent, renamed *Dirent,
 }
 
 // Bind calls i.InodeOperations.Bind with i as the directory.
-func (i *Inode) Bind(ctx context.Context, name string, data transport.BoundEndpoint, perm FilePermissions) (*Dirent, error) {
+func (i *Inode) Bind(ctx context.Context, parent *Dirent, name string, data transport.BoundEndpoint, perm FilePermissions) (*Dirent, error) {
 	if i.overlay != nil {
-		return overlayBind(ctx, i.overlay, name, data, perm)
+		return overlayBind(ctx, i.overlay, parent, name, data, perm)
 	}
 	return i.InodeOperations.Bind(ctx, i, name, data, perm)
 }
diff --git a/pkg/sentry/fs/inode_overlay.go b/pkg/sentry/fs/inode_overlay.go
index cdffe173b..06506fb20 100644
--- a/pkg/sentry/fs/inode_overlay.go
+++ b/pkg/sentry/fs/inode_overlay.go
@@ -398,14 +398,14 @@ func overlayRename(ctx context.Context, o *overlayEntry, oldParent *Dirent, rena
 	return nil
 }
 
-func overlayBind(ctx context.Context, o *overlayEntry, name string, data transport.BoundEndpoint, perm FilePermissions) (*Dirent, error) {
+func overlayBind(ctx context.Context, o *overlayEntry, parent *Dirent, name string, data transport.BoundEndpoint, perm FilePermissions) (*Dirent, error) {
+	if err := copyUp(ctx, parent); err != nil {
+		return nil, err
+	}
+
 	o.copyMu.RLock()
 	defer o.copyMu.RUnlock()
-	// We do not support doing anything exciting with sockets unless there
-	// is already a directory in the upper filesystem.
-	if o.upper == nil {
-		return nil, syserror.EOPNOTSUPP
-	}
+
 	d, err := o.upper.InodeOperations.Bind(ctx, o.upper, name, data, perm)
 	if err != nil {
 		return nil, err
diff --git a/pkg/sentry/fs/proc/BUILD b/pkg/sentry/fs/proc/BUILD
index d19c360e0..1728fe0b5 100644
--- a/pkg/sentry/fs/proc/BUILD
+++ b/pkg/sentry/fs/proc/BUILD
@@ -45,6 +45,7 @@ go_library(
         "//pkg/sentry/kernel/time",
         "//pkg/sentry/limits",
         "//pkg/sentry/mm",
+        "//pkg/sentry/socket",
         "//pkg/sentry/socket/rpcinet",
         "//pkg/sentry/socket/unix",
         "//pkg/sentry/socket/unix/transport",
diff --git a/pkg/sentry/fs/proc/inode.go b/pkg/sentry/fs/proc/inode.go
index 379569823..986bc0a45 100644
--- a/pkg/sentry/fs/proc/inode.go
+++ b/pkg/sentry/fs/proc/inode.go
@@ -21,11 +21,14 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/proc/device"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/mm"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 )
 
 // taskOwnedInodeOps wraps an fs.InodeOperations and overrides the UnstableAttr
-// method to return the task as the owner.
+// method to return either the task or root as the owner, depending on the
+// task's dumpability.
 //
 // +stateify savable
 type taskOwnedInodeOps struct {
@@ -41,9 +44,42 @@ func (i *taskOwnedInodeOps) UnstableAttr(ctx context.Context, inode *fs.Inode) (
 	if err != nil {
 		return fs.UnstableAttr{}, err
 	}
-	// Set the task owner as the file owner.
+
+	// By default, set the task owner as the file owner.
 	creds := i.t.Credentials()
 	uattr.Owner = fs.FileOwner{creds.EffectiveKUID, creds.EffectiveKGID}
+
+	// Linux doesn't apply dumpability adjustments to world
+	// readable/executable directories so that applications can stat
+	// /proc/PID to determine the effective UID of a process. See
+	// fs/proc/base.c:task_dump_owner.
+	if fs.IsDir(inode.StableAttr) && uattr.Perms == fs.FilePermsFromMode(0555) {
+		return uattr, nil
+	}
+
+	// If the task is not dumpable, then root (in the namespace preferred)
+	// owns the file.
+	var m *mm.MemoryManager
+	i.t.WithMuLocked(func(t *kernel.Task) {
+		m = t.MemoryManager()
+	})
+
+	if m == nil {
+		uattr.Owner.UID = auth.RootKUID
+		uattr.Owner.GID = auth.RootKGID
+	} else if m.Dumpability() != mm.UserDumpable {
+		if kuid := creds.UserNamespace.MapToKUID(auth.RootUID); kuid.Ok() {
+			uattr.Owner.UID = kuid
+		} else {
+			uattr.Owner.UID = auth.RootKUID
+		}
+		if kgid := creds.UserNamespace.MapToKGID(auth.RootGID); kgid.Ok() {
+			uattr.Owner.GID = kgid
+		} else {
+			uattr.Owner.GID = auth.RootKGID
+		}
+	}
+
 	return uattr, nil
 }
 
diff --git a/pkg/sentry/fs/proc/net.go b/pkg/sentry/fs/proc/net.go
index 4a107c739..034950158 100644
--- a/pkg/sentry/fs/proc/net.go
+++ b/pkg/sentry/fs/proc/net.go
@@ -27,6 +27,7 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/ramfs"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/inet"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/socket"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/unix"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/unix/transport"
 )
@@ -213,17 +214,18 @@ func (n *netUnix) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle) ([]s
 	fmt.Fprintf(&buf, "Num       RefCount Protocol Flags    Type St Inode Path\n")
 
 	// Entries
-	for _, sref := range n.k.ListSockets(linux.AF_UNIX) {
-		s := sref.Get()
+	for _, se := range n.k.ListSockets() {
+		s := se.Sock.Get()
 		if s == nil {
-			log.Debugf("Couldn't resolve weakref %v in socket table, racing with destruction?", sref)
+			log.Debugf("Couldn't resolve weakref %v in socket table, racing with destruction?", se.Sock)
 			continue
 		}
 		sfile := s.(*fs.File)
-		sops, ok := sfile.FileOperations.(*unix.SocketOperations)
-		if !ok {
-			panic(fmt.Sprintf("Found non-unix socket file in unix socket table: %+v", sfile))
+		if family, _, _ := sfile.FileOperations.(socket.Socket).Type(); family != linux.AF_UNIX {
+			// Not a unix socket.
+			continue
 		}
+		sops := sfile.FileOperations.(*unix.SocketOperations)
 
 		addr, err := sops.Endpoint().GetLocalAddress()
 		if err != nil {
@@ -240,24 +242,6 @@ func (n *netUnix) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle) ([]s
 			}
 		}
 
-		var sockState int
-		switch sops.Endpoint().Type() {
-		case linux.SOCK_DGRAM:
-			sockState = linux.SS_CONNECTING
-			// Unlike Linux, we don't have unbound connection-less sockets,
-			// so no SS_DISCONNECTING.
-
-		case linux.SOCK_SEQPACKET:
-			fallthrough
-		case linux.SOCK_STREAM:
-			// Connectioned.
-			if sops.Endpoint().(transport.ConnectingEndpoint).Connected() {
-				sockState = linux.SS_CONNECTED
-			} else {
-				sockState = linux.SS_UNCONNECTED
-			}
-		}
-
 		// In the socket entry below, the value for the 'Num' field requires
 		// some consideration. Linux prints the address to the struct
 		// unix_sock representing a socket in the kernel, but may redact the
@@ -282,7 +266,7 @@ func (n *netUnix) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle) ([]s
 			0,                             // Protocol, always 0 for UDS.
 			sockFlags,                     // Flags.
 			sops.Endpoint().Type(),        // Type.
-			sockState,                     // State.
+			sops.State(),                  // State.
 			sfile.InodeID(),               // Inode.
 		)
 
diff --git a/pkg/sentry/fs/proc/task.go b/pkg/sentry/fs/proc/task.go
index 77e03d349..21a965f90 100644
--- a/pkg/sentry/fs/proc/task.go
+++ b/pkg/sentry/fs/proc/task.go
@@ -96,7 +96,7 @@ func (p *proc) newTaskDir(t *kernel.Task, msrc *fs.MountSource, showSubtasks boo
 		contents["cgroup"] = newCGroupInode(t, msrc, p.cgroupControllers)
 	}
 
-	// TODO(b/31916171): Set EUID/EGID based on dumpability.
+	// N.B. taskOwnedInodeOps enforces dumpability-based ownership.
 	d := &taskDir{
 		Dir: *ramfs.NewDir(t, contents, fs.RootOwner, fs.FilePermsFromMode(0555)),
 		t:   t,
@@ -667,6 +667,21 @@ func newComm(t *kernel.Task, msrc *fs.MountSource) *fs.Inode {
 	return newProcInode(c, msrc, fs.SpecialFile, t)
 }
 
+// Check implements fs.InodeOperations.Check.
+func (c *comm) Check(ctx context.Context, inode *fs.Inode, p fs.PermMask) bool {
+	// This file can always be read or written by members of the same
+	// thread group. See fs/proc/base.c:proc_tid_comm_permission.
+	//
+	// N.B. This check is currently a no-op as we don't yet support writing
+	// and this file is world-readable anyways.
+	t := kernel.TaskFromContext(ctx)
+	if t != nil && t.ThreadGroup() == c.t.ThreadGroup() && !p.Execute {
+		return true
+	}
+
+	return fs.ContextCanAccessFile(ctx, inode, p)
+}
+
 // GetFile implements fs.InodeOperations.GetFile.
 func (c *comm) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
 	return fs.NewFile(ctx, dirent, flags, &commFile{t: c.t}), nil
diff --git a/pkg/sentry/fs/timerfd/timerfd.go b/pkg/sentry/fs/timerfd/timerfd.go
index bce5f091d..c1721f434 100644
--- a/pkg/sentry/fs/timerfd/timerfd.go
+++ b/pkg/sentry/fs/timerfd/timerfd.go
@@ -54,6 +54,8 @@ type TimerOperations struct {
 // NewFile returns a timerfd File that receives time from c.
 func NewFile(ctx context.Context, c ktime.Clock) *fs.File {
 	dirent := fs.NewDirent(anon.NewInode(ctx), "anon_inode:[timerfd]")
+	// Release the initial dirent reference after NewFile takes a reference.
+	defer dirent.DecRef()
 	tops := &TimerOperations{}
 	tops.timer = ktime.NewTimer(c, tops)
 	// Timerfds reject writes, but the Write flag must be set in order to
diff --git a/pkg/sentry/fs/tmpfs/fs.go b/pkg/sentry/fs/tmpfs/fs.go
index b7c29a4d1..83e1bf247 100644
--- a/pkg/sentry/fs/tmpfs/fs.go
+++ b/pkg/sentry/fs/tmpfs/fs.go
@@ -34,6 +34,16 @@ const (
 	// GID for the root directory.
 	rootGIDKey = "gid"
 
+	// cacheKey sets the caching policy for the mount.
+	cacheKey = "cache"
+
+	// cacheAll uses the virtual file system cache for everything (default).
+	cacheAll = "cache"
+
+	// cacheRevalidate allows dirents to be cached, but revalidates them on each
+	// lookup.
+	cacheRevalidate = "revalidate"
+
 	// TODO(edahlgren/mpratt): support a tmpfs size limit.
 	// size = "size"
 
@@ -122,15 +132,24 @@ func (f *Filesystem) Mount(ctx context.Context, device string, flags fs.MountSou
 		delete(options, rootGIDKey)
 	}
 
+	// Construct a mount which will follow the cache options provided.
+	var msrc *fs.MountSource
+	switch options[cacheKey] {
+	case "", cacheAll:
+		msrc = fs.NewCachingMountSource(f, flags)
+	case cacheRevalidate:
+		msrc = fs.NewRevalidatingMountSource(f, flags)
+	default:
+		return nil, fmt.Errorf("invalid cache policy option %q", options[cacheKey])
+	}
+	delete(options, cacheKey)
+
 	// Fail if the caller passed us more options than we can parse. They may be
 	// expecting us to set something we can't set.
 	if len(options) > 0 {
 		return nil, fmt.Errorf("unsupported mount options: %v", options)
 	}
 
-	// Construct a mount which will cache dirents.
-	msrc := fs.NewCachingMountSource(f, flags)
-
 	// Construct the tmpfs root.
 	return NewDir(ctx, nil, owner, perms, msrc), nil
 }