Record VFS2 sockets in global socket map.

Updates #1476, #1478, #1484, #1485.

PiperOrigin-RevId: 304845354

pkg/sentry/fsimpl/proc/BUILD

@@ -22,7 +22,6 @@ go_library(
         "//pkg/log",
         "//pkg/refs",
         "//pkg/safemem",
-        "//pkg/sentry/fs",
         "//pkg/sentry/fsbridge",
         "//pkg/sentry/fsimpl/kernfs",
         "//pkg/sentry/inet",

pkg/sentry/fsimpl/proc/task_net.go

@@ -24,7 +24,6 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/log"
-	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
 	"gvisor.dev/gvisor/pkg/sentry/inet"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
@@ -32,6 +31,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/socket"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/usermem"
@@ -206,22 +206,21 @@ var _ dynamicInode = (*netUnixData)(nil)
 func (n *netUnixData) Generate(ctx context.Context, buf *bytes.Buffer) error {
 	buf.WriteString("Num       RefCount Protocol Flags    Type St Inode Path\n")
 	for _, se := range n.kernel.ListSockets() {
-		s := se.Sock.Get()
-		if s == nil {
-			log.Debugf("Couldn't resolve weakref %v in socket table, racing with destruction?", se.Sock)
+		s := se.SockVFS2
+		if !s.TryIncRef() {
+			log.Debugf("Couldn't get reference on %v in socket table, racing with destruction?", s)
 			continue
 		}
-		sfile := s.(*fs.File)
-		if family, _, _ := sfile.FileOperations.(socket.Socket).Type(); family != linux.AF_UNIX {
+		if family, _, _ := s.Impl().(socket.SocketVFS2).Type(); family != linux.AF_UNIX {
 			s.DecRef()
 			// Not a unix socket.
 			continue
 		}
-		sops := sfile.FileOperations.(*unix.SocketOperations)
+		sops := s.Impl().(*unix.SocketVFS2)
 
 		addr, err := sops.Endpoint().GetLocalAddress()
 		if err != nil {
-			log.Warningf("Failed to retrieve socket name from %+v: %v", sfile, err)
+			log.Warningf("Failed to retrieve socket name from %+v: %v", s, err)
 			addr.Addr = "<unknown>"
 		}
 
@@ -234,6 +233,15 @@ func (n *netUnixData) Generate(ctx context.Context, buf *bytes.Buffer) error {
 			}
 		}
 
+		// Get inode number.
+		var ino uint64
+		stat, statErr := s.Stat(ctx, vfs.StatOptions{Mask: linux.STATX_INO})
+		if statErr != nil || stat.Mask&linux.STATX_INO == 0 {
+			log.Warningf("Failed to retrieve ino for socket file: %v", statErr)
+		} else {
+			ino = stat.Ino
+		}
+
 		// 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
@@ -252,14 +260,14 @@ func (n *netUnixData) Generate(ctx context.Context, buf *bytes.Buffer) error {
 		// the definition of this struct changes over time.
 		//
 		// For now, we always redact this pointer.
-		fmt.Fprintf(buf, "%#016p: %08X %08X %08X %04X %02X %5d",
+		fmt.Fprintf(buf, "%#016p: %08X %08X %08X %04X %02X %8d",
 			(*unix.SocketOperations)(nil), // Num, pointer to kernel socket struct.
-			sfile.ReadRefs()-1,            // RefCount, don't count our own ref.
+			s.Refs()-1,                    // RefCount, don't count our own ref.
 			0,                             // Protocol, always 0 for UDS.
 			sockFlags,                     // Flags.
 			sops.Endpoint().Type(),        // Type.
 			sops.State(),                  // State.
-			sfile.InodeID(),               // Inode.
+			ino,                           // Inode.
 		)
 
 		// Path
@@ -341,15 +349,14 @@ func commonGenerateTCP(ctx context.Context, buf *bytes.Buffer, k *kernel.Kernel,
 	t := kernel.TaskFromContext(ctx)
 
 	for _, se := range k.ListSockets() {
-		s := se.Sock.Get()
-		if s == nil {
-			log.Debugf("Couldn't resolve weakref with ID %v in socket table, racing with destruction?", se.ID)
+		s := se.SockVFS2
+		if !s.TryIncRef() {
+			log.Debugf("Couldn't get reference on %v in socket table, racing with destruction?", s)
 			continue
 		}
-		sfile := s.(*fs.File)
-		sops, ok := sfile.FileOperations.(socket.Socket)
+		sops, ok := s.Impl().(socket.SocketVFS2)
 		if !ok {
-			panic(fmt.Sprintf("Found non-socket file in socket table: %+v", sfile))
+			panic(fmt.Sprintf("Found non-socket file in socket table: %+v", s))
 		}
 		if fa, stype, _ := sops.Type(); !(family == fa && stype == linux.SOCK_STREAM) {
 			s.DecRef()
@@ -398,14 +405,15 @@ func commonGenerateTCP(ctx context.Context, buf *bytes.Buffer, k *kernel.Kernel,
 		// Unimplemented.
 		fmt.Fprintf(buf, "%08X ", 0)
 
+		stat, statErr := s.Stat(ctx, vfs.StatOptions{Mask: linux.STATX_UID | linux.STATX_INO})
+
 		// Field: uid.
-		uattr, err := sfile.Dirent.Inode.UnstableAttr(ctx)
-		if err != nil {
-			log.Warningf("Failed to retrieve unstable attr for socket file: %v", err)
+		if statErr != nil || stat.Mask&linux.STATX_UID == 0 {
+			log.Warningf("Failed to retrieve uid for socket file: %v", statErr)
 			fmt.Fprintf(buf, "%5d ", 0)
 		} else {
 			creds := auth.CredentialsFromContext(ctx)
-			fmt.Fprintf(buf, "%5d ", uint32(uattr.Owner.UID.In(creds.UserNamespace).OrOverflow()))
+			fmt.Fprintf(buf, "%5d ", uint32(auth.KUID(stat.UID).In(creds.UserNamespace).OrOverflow()))
 		}
 
 		// Field: timeout; number of unanswered 0-window probes.
@@ -413,11 +421,16 @@ func commonGenerateTCP(ctx context.Context, buf *bytes.Buffer, k *kernel.Kernel,
 		fmt.Fprintf(buf, "%8d ", 0)
 
 		// Field: inode.
-		fmt.Fprintf(buf, "%8d ", sfile.InodeID())
+		if statErr != nil || stat.Mask&linux.STATX_INO == 0 {
+			log.Warningf("Failed to retrieve inode for socket file: %v", statErr)
+			fmt.Fprintf(buf, "%8d ", 0)
+		} else {
+			fmt.Fprintf(buf, "%8d ", stat.Ino)
+		}
 
 		// Field: refcount. Don't count the ref we obtain while deferencing
 		// the weakref to this socket.
-		fmt.Fprintf(buf, "%d ", sfile.ReadRefs()-1)
+		fmt.Fprintf(buf, "%d ", s.Refs()-1)
 
 		// Field: Socket struct address. Redacted due to the same reason as
 		// the 'Num' field in /proc/net/unix, see netUnix.ReadSeqFileData.
@@ -499,15 +512,14 @@ func (d *netUDPData) Generate(ctx context.Context, buf *bytes.Buffer) error {
 	t := kernel.TaskFromContext(ctx)
 
 	for _, se := range d.kernel.ListSockets() {
-		s := se.Sock.Get()
-		if s == nil {
-			log.Debugf("Couldn't resolve weakref with ID %v in socket table, racing with destruction?", se.ID)
+		s := se.SockVFS2
+		if !s.TryIncRef() {
+			log.Debugf("Couldn't get reference on %v in socket table, racing with destruction?", s)
 			continue
 		}
-		sfile := s.(*fs.File)
-		sops, ok := sfile.FileOperations.(socket.Socket)
+		sops, ok := s.Impl().(socket.SocketVFS2)
 		if !ok {
-			panic(fmt.Sprintf("Found non-socket file in socket table: %+v", sfile))
+			panic(fmt.Sprintf("Found non-socket file in socket table: %+v", s))
 		}
 		if family, stype, _ := sops.Type(); family != linux.AF_INET || stype != linux.SOCK_DGRAM {
 			s.DecRef()
@@ -551,25 +563,31 @@ func (d *netUDPData) Generate(ctx context.Context, buf *bytes.Buffer) error {
 		// Field: retrnsmt. Always 0 for UDP.
 		fmt.Fprintf(buf, "%08X ", 0)
 
+		stat, statErr := s.Stat(ctx, vfs.StatOptions{Mask: linux.STATX_UID | linux.STATX_INO})
+
 		// Field: uid.
-		uattr, err := sfile.Dirent.Inode.UnstableAttr(ctx)
-		if err != nil {
-			log.Warningf("Failed to retrieve unstable attr for socket file: %v", err)
+		if statErr != nil || stat.Mask&linux.STATX_UID == 0 {
+			log.Warningf("Failed to retrieve uid for socket file: %v", statErr)
 			fmt.Fprintf(buf, "%5d ", 0)
 		} else {
 			creds := auth.CredentialsFromContext(ctx)
-			fmt.Fprintf(buf, "%5d ", uint32(uattr.Owner.UID.In(creds.UserNamespace).OrOverflow()))
+			fmt.Fprintf(buf, "%5d ", uint32(auth.KUID(stat.UID).In(creds.UserNamespace).OrOverflow()))
 		}
 
 		// Field: timeout. Always 0 for UDP.
 		fmt.Fprintf(buf, "%8d ", 0)
 
 		// Field: inode.
-		fmt.Fprintf(buf, "%8d ", sfile.InodeID())
+		if statErr != nil || stat.Mask&linux.STATX_INO == 0 {
+			log.Warningf("Failed to retrieve inode for socket file: %v", statErr)
+			fmt.Fprintf(buf, "%8d ", 0)
+		} else {
+			fmt.Fprintf(buf, "%8d ", stat.Ino)
+		}
 
 		// Field: ref; reference count on the socket inode. Don't count the ref
 		// we obtain while deferencing the weakref to this socket.
-		fmt.Fprintf(buf, "%d ", sfile.ReadRefs()-1)
+		fmt.Fprintf(buf, "%d ", s.Refs()-1)
 
 		// Field: Socket struct address. Redacted due to the same reason as
 		// the 'Num' field in /proc/net/unix, see netUnix.ReadSeqFileData.

pkg/sentry/kernel/kernel.go

@@ -1445,9 +1445,10 @@ func (k *Kernel) SupervisorContext() context.Context {
 // +stateify savable
 type SocketEntry struct {
 	socketEntry
-	k    *Kernel
-	Sock *refs.WeakRef
-	ID   uint64 // Socket table entry number.
+	k        *Kernel
+	Sock     *refs.WeakRef
+	SockVFS2 *vfs.FileDescription
+	ID       uint64 // Socket table entry number.
 }
 
 // WeakRefGone implements refs.WeakRefUser.WeakRefGone.
@@ -1470,7 +1471,30 @@ func (k *Kernel) RecordSocket(sock *fs.File) {
 	k.extMu.Unlock()
 }
 
+// RecordSocketVFS2 adds a VFS2 socket to the system-wide socket table for
+// tracking.
+//
+// Precondition: Caller must hold a reference to sock.
+//
+// Note that the socket table will not hold a reference on the
+// vfs.FileDescription, because we do not support weak refs on VFS2 files.
+func (k *Kernel) RecordSocketVFS2(sock *vfs.FileDescription) {
+	k.extMu.Lock()
+	id := k.nextSocketEntry
+	k.nextSocketEntry++
+	s := &SocketEntry{
+		k:        k,
+		ID:       id,
+		SockVFS2: sock,
+	}
+	k.sockets.PushBack(s)
+	k.extMu.Unlock()
+}
+
 // ListSockets returns a snapshot of all sockets.
+//
+// Callers of ListSockets() in VFS2 should use SocketEntry.SockVFS2.TryIncRef()
+// to get a reference on a socket in the table.
 func (k *Kernel) ListSockets() []*SocketEntry {
 	k.extMu.Lock()
 	var socks []*SocketEntry

pkg/sentry/socket/socket.go

@@ -269,7 +269,7 @@ func NewVFS2(t *kernel.Task, family int, stype linux.SockType, protocol int) (*v
 			return nil, err
 		}
 		if s != nil {
-			// TODO: Add vfs2 sockets to global socket table.
+			t.Kernel().RecordSocketVFS2(s)
 			return s, nil
 		}
 	}
@@ -291,7 +291,9 @@ func PairVFS2(t *kernel.Task, family int, stype linux.SockType, protocol int) (*
 			return nil, nil, err
 		}
 		if s1 != nil && s2 != nil {
-			// TODO: Add vfs2 sockets to global socket table.
+			k := t.Kernel()
+			k.RecordSocketVFS2(s1)
+			k.RecordSocketVFS2(s2)
 			return s1, s2, nil
 		}
 	}

pkg/sentry/socket/unix/unix_vfs2.go

@@ -141,7 +141,7 @@ func (s *SocketVFS2) Accept(t *kernel.Task, peerRequested bool, flags int, block
 		return 0, nil, 0, syserr.FromError(e)
 	}
 
-	// TODO: add vfs2 sockets to global table.
+	t.Kernel().RecordSocketVFS2(ns)
 	return fd, addr, addrLen, nil
 }
 

pkg/sentry/vfs/file_description.go

@@ -182,6 +182,12 @@ func (fd *FileDescription) DecRef() {
 	}
 }
 
+// Refs returns the current number of references. The returned count
+// is inherently racy and is unsafe to use without external synchronization.
+func (fd *FileDescription) Refs() int64 {
+	return atomic.LoadInt64(&fd.refs)
+}
+
 // Mount returns the mount on which fd was opened. It does not take a reference
 // on the returned Mount.
 func (fd *FileDescription) Mount() *Mount {