Add FileDescriptionImpl for Unix sockets.

This change involves several steps:
- Refactor the VFS1 unix socket implementation to share methods between VFS1
  and VFS2 where possible. Re-implement the rest.
- Override the default PRead, Read, PWrite, Write, Ioctl, Release methods in
  FileDescriptionDefaultImpl.
- Add functions to create and initialize a new Dentry/Inode and FileDescription
  for a Unix socket file.

Updates #1476

PiperOrigin-RevId: 304689796

1 files changed, 64 insertions, 25 deletions

diff --git a/pkg/sentry/socket/unix/unix.go b/pkg/sentry/socket/unix/unix.go
index 4d30aa714..7c64f30fa 100644
--- a/pkg/sentry/socket/unix/unix.go
+++ b/pkg/sentry/socket/unix/unix.go
@@ -23,6 +23,7 @@ import (
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/refs"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
@@ -33,6 +34,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/socket/control"
 	"gvisor.dev/gvisor/pkg/sentry/socket/netstack"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/tcpip"
@@ -52,11 +54,8 @@ type SocketOperations struct {
 	fsutil.FileNoSplice             `state:"nosave"`
 	fsutil.FileNoopFlush            `state:"nosave"`
 	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
-	refs.AtomicRefCount
-	socket.SendReceiveTimeout
 
-	ep    transport.Endpoint
-	stype linux.SockType
+	socketOpsCommon
 }
 
 // New creates a new unix socket.
@@ -75,16 +74,29 @@ func NewWithDirent(ctx context.Context, d *fs.Dirent, ep transport.Endpoint, sty
 	}
 
 	s := SocketOperations{
-		ep:    ep,
-		stype: stype,
+		socketOpsCommon: socketOpsCommon{
+			ep:    ep,
+			stype: stype,
+		},
 	}
 	s.EnableLeakCheck("unix.SocketOperations")
 
 	return fs.NewFile(ctx, d, flags, &s)
 }
 
+// socketOpsCommon contains the socket operations common to VFS1 and VFS2.
+//
+// +stateify savable
+type socketOpsCommon struct {
+	refs.AtomicRefCount
+	socket.SendReceiveTimeout
+
+	ep    transport.Endpoint
+	stype linux.SockType
+}
+
 // DecRef implements RefCounter.DecRef.
-func (s *SocketOperations) DecRef() {
+func (s *socketOpsCommon) DecRef() {
 	s.DecRefWithDestructor(func() {
 		s.ep.Close()
 	})
@@ -97,7 +109,7 @@ func (s *SocketOperations) Release() {
 	s.DecRef()
 }
 
-func (s *SocketOperations) isPacket() bool {
+func (s *socketOpsCommon) isPacket() bool {
 	switch s.stype {
 	case linux.SOCK_DGRAM, linux.SOCK_SEQPACKET:
 		return true
@@ -110,7 +122,7 @@ func (s *SocketOperations) isPacket() bool {
 }
 
 // Endpoint extracts the transport.Endpoint.
-func (s *SocketOperations) Endpoint() transport.Endpoint {
+func (s *socketOpsCommon) Endpoint() transport.Endpoint {
 	return s.ep
 }
 
@@ -143,7 +155,7 @@ func extractPath(sockaddr []byte) (string, *syserr.Error) {
 
 // GetPeerName implements the linux syscall getpeername(2) for sockets backed by
 // a transport.Endpoint.
-func (s *SocketOperations) GetPeerName(t *kernel.Task) (linux.SockAddr, uint32, *syserr.Error) {
+func (s *socketOpsCommon) GetPeerName(t *kernel.Task) (linux.SockAddr, uint32, *syserr.Error) {
 	addr, err := s.ep.GetRemoteAddress()
 	if err != nil {
 		return nil, 0, syserr.TranslateNetstackError(err)
@@ -155,7 +167,7 @@ func (s *SocketOperations) GetPeerName(t *kernel.Task) (linux.SockAddr, uint32,
 
 // GetSockName implements the linux syscall getsockname(2) for sockets backed by
 // a transport.Endpoint.
-func (s *SocketOperations) GetSockName(t *kernel.Task) (linux.SockAddr, uint32, *syserr.Error) {
+func (s *socketOpsCommon) GetSockName(t *kernel.Task) (linux.SockAddr, uint32, *syserr.Error) {
 	addr, err := s.ep.GetLocalAddress()
 	if err != nil {
 		return nil, 0, syserr.TranslateNetstackError(err)
@@ -178,7 +190,7 @@ func (s *SocketOperations) GetSockOpt(t *kernel.Task, level, name int, outPtr us
 
 // Listen implements the linux syscall listen(2) for sockets backed by
 // a transport.Endpoint.
-func (s *SocketOperations) Listen(t *kernel.Task, backlog int) *syserr.Error {
+func (s *socketOpsCommon) Listen(t *kernel.Task, backlog int) *syserr.Error {
 	return s.ep.Listen(backlog)
 }
 
@@ -310,6 +322,8 @@ func (s *SocketOperations) Bind(t *kernel.Task, sockaddr []byte) *syserr.Error {
 			}
 
 			// Create the socket.
+			//
+			// TODO(gvisor.dev/issue/2324): Correctly set file permissions.
 			childDir, err := d.Bind(t, t.FSContext().RootDirectory(), name, bep, fs.FilePermissions{User: fs.PermMask{Read: true}})
 			if err != nil {
 				return syserr.ErrPortInUse
@@ -345,6 +359,31 @@ func extractEndpoint(t *kernel.Task, sockaddr []byte) (transport.BoundEndpoint,
 		return ep, nil
 	}
 
+	if kernel.VFS2Enabled {
+		p := fspath.Parse(path)
+		root := t.FSContext().RootDirectoryVFS2()
+		start := root
+		relPath := !p.Absolute
+		if relPath {
+			start = t.FSContext().WorkingDirectoryVFS2()
+		}
+		pop := vfs.PathOperation{
+			Root:               root,
+			Start:              start,
+			Path:               p,
+			FollowFinalSymlink: true,
+		}
+		ep, e := t.Kernel().VFS().BoundEndpointAt(t, t.Credentials(), &pop)
+		root.DecRef()
+		if relPath {
+			start.DecRef()
+		}
+		if e != nil {
+			return nil, syserr.FromError(e)
+		}
+		return ep, nil
+	}
+
 	// Find the node in the filesystem.
 	root := t.FSContext().RootDirectory()
 	cwd := t.FSContext().WorkingDirectory()
@@ -363,12 +402,11 @@ func extractEndpoint(t *kernel.Task, sockaddr []byte) (transport.BoundEndpoint,
 		// No socket!
 		return nil, syserr.ErrConnectionRefused
 	}
-
 	return ep, nil
 }
 
 // Connect implements the linux syscall connect(2) for unix sockets.
-func (s *SocketOperations) Connect(t *kernel.Task, sockaddr []byte, blocking bool) *syserr.Error {
+func (s *socketOpsCommon) Connect(t *kernel.Task, sockaddr []byte, blocking bool) *syserr.Error {
 	ep, err := extractEndpoint(t, sockaddr)
 	if err != nil {
 		return err
@@ -379,7 +417,7 @@ func (s *SocketOperations) Connect(t *kernel.Task, sockaddr []byte, blocking boo
 	return s.ep.Connect(t, ep)
 }
 
-// Writev implements fs.FileOperations.Write.
+// Write implements fs.FileOperations.Write.
 func (s *SocketOperations) Write(ctx context.Context, _ *fs.File, src usermem.IOSequence, _ int64) (int64, error) {
 	t := kernel.TaskFromContext(ctx)
 	ctrl := control.New(t, s.ep, nil)
@@ -399,7 +437,7 @@ func (s *SocketOperations) Write(ctx context.Context, _ *fs.File, src usermem.IO
 
 // SendMsg implements the linux syscall sendmsg(2) for unix sockets backed by
 // a transport.Endpoint.
-func (s *SocketOperations) SendMsg(t *kernel.Task, src usermem.IOSequence, to []byte, flags int, haveDeadline bool, deadline ktime.Time, controlMessages socket.ControlMessages) (int, *syserr.Error) {
+func (s *socketOpsCommon) SendMsg(t *kernel.Task, src usermem.IOSequence, to []byte, flags int, haveDeadline bool, deadline ktime.Time, controlMessages socket.ControlMessages) (int, *syserr.Error) {
 	w := EndpointWriter{
 		Ctx:      t,
 		Endpoint: s.ep,
@@ -453,27 +491,27 @@ func (s *SocketOperations) SendMsg(t *kernel.Task, src usermem.IOSequence, to []
 }
 
 // Passcred implements transport.Credentialer.Passcred.
-func (s *SocketOperations) Passcred() bool {
+func (s *socketOpsCommon) Passcred() bool {
 	return s.ep.Passcred()
 }
 
 // ConnectedPasscred implements transport.Credentialer.ConnectedPasscred.
-func (s *SocketOperations) ConnectedPasscred() bool {
+func (s *socketOpsCommon) ConnectedPasscred() bool {
 	return s.ep.ConnectedPasscred()
 }
 
 // Readiness implements waiter.Waitable.Readiness.
-func (s *SocketOperations) Readiness(mask waiter.EventMask) waiter.EventMask {
+func (s *socketOpsCommon) Readiness(mask waiter.EventMask) waiter.EventMask {
 	return s.ep.Readiness(mask)
 }
 
 // EventRegister implements waiter.Waitable.EventRegister.
-func (s *SocketOperations) EventRegister(e *waiter.Entry, mask waiter.EventMask) {
+func (s *socketOpsCommon) EventRegister(e *waiter.Entry, mask waiter.EventMask) {
 	s.ep.EventRegister(e, mask)
 }
 
 // EventUnregister implements waiter.Waitable.EventUnregister.
-func (s *SocketOperations) EventUnregister(e *waiter.Entry) {
+func (s *socketOpsCommon) EventUnregister(e *waiter.Entry) {
 	s.ep.EventUnregister(e)
 }
 
@@ -485,7 +523,7 @@ func (s *SocketOperations) SetSockOpt(t *kernel.Task, level int, name int, optVa
 
 // Shutdown implements the linux syscall shutdown(2) for sockets backed by
 // a transport.Endpoint.
-func (s *SocketOperations) Shutdown(t *kernel.Task, how int) *syserr.Error {
+func (s *socketOpsCommon) Shutdown(t *kernel.Task, how int) *syserr.Error {
 	f, err := netstack.ConvertShutdown(how)
 	if err != nil {
 		return err
@@ -511,7 +549,7 @@ func (s *SocketOperations) Read(ctx context.Context, _ *fs.File, dst usermem.IOS
 
 // RecvMsg implements the linux syscall recvmsg(2) for sockets backed by
 // a transport.Endpoint.
-func (s *SocketOperations) RecvMsg(t *kernel.Task, dst usermem.IOSequence, flags int, haveDeadline bool, deadline ktime.Time, senderRequested bool, controlDataLen uint64) (n int, msgFlags int, senderAddr linux.SockAddr, senderAddrLen uint32, controlMessages socket.ControlMessages, err *syserr.Error) {
+func (s *socketOpsCommon) RecvMsg(t *kernel.Task, dst usermem.IOSequence, flags int, haveDeadline bool, deadline ktime.Time, senderRequested bool, controlDataLen uint64) (n int, msgFlags int, senderAddr linux.SockAddr, senderAddrLen uint32, controlMessages socket.ControlMessages, err *syserr.Error) {
 	trunc := flags&linux.MSG_TRUNC != 0
 	peek := flags&linux.MSG_PEEK != 0
 	dontWait := flags&linux.MSG_DONTWAIT != 0
@@ -648,12 +686,12 @@ func (s *SocketOperations) RecvMsg(t *kernel.Task, dst usermem.IOSequence, flags
 }
 
 // State implements socket.Socket.State.
-func (s *SocketOperations) State() uint32 {
+func (s *socketOpsCommon) State() uint32 {
 	return s.ep.State()
 }
 
 // Type implements socket.Socket.Type.
-func (s *SocketOperations) Type() (family int, skType linux.SockType, protocol int) {
+func (s *socketOpsCommon) Type() (family int, skType linux.SockType, protocol int) {
 	// Unix domain sockets always have a protocol of 0.
 	return linux.AF_UNIX, s.stype, 0
 }
@@ -706,4 +744,5 @@ func (*provider) Pair(t *kernel.Task, stype linux.SockType, protocol int) (*fs.F
 
 func init() {
 	socket.RegisterProvider(linux.AF_UNIX, &provider{})
+	socket.RegisterProviderVFS2(linux.AF_UNIX, &providerVFS2{})
 }