Add TTY support on VFS2 to runsc

Updates #1623, #1487

PiperOrigin-RevId: 309777922

8 files changed, 227 insertions, 75 deletions

diff --git a/pkg/sentry/control/BUILD b/pkg/sentry/control/BUILD
index d16d78aa5..e74275d2d 100644
--- a/pkg/sentry/control/BUILD
+++ b/pkg/sentry/control/BUILD
@@ -20,9 +20,11 @@ go_library(
         "//pkg/fd",
         "//pkg/fspath",
         "//pkg/log",
+        "//pkg/sentry/fdimport",
         "//pkg/sentry/fs",
         "//pkg/sentry/fs/host",
         "//pkg/sentry/fsbridge",
+        "//pkg/sentry/fsimpl/host",
         "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/kernel/time",
@@ -36,6 +38,7 @@ go_library(
         "//pkg/syserror",
         "//pkg/tcpip/link/sniffer",
         "//pkg/urpc",
+        "@org_golang_x_sys//unix:go_default_library",
     ],
 )
 
diff --git a/pkg/sentry/control/proc.go b/pkg/sentry/control/proc.go
index b51fb3959..2ed17ee09 100644
--- a/pkg/sentry/control/proc.go
+++ b/pkg/sentry/control/proc.go
@@ -24,13 +24,16 @@ import (
 	"text/tabwriter"
 	"time"
 
+	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sentry/fdimport"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/host"
 	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
+	hostvfs2 "gvisor.dev/gvisor/pkg/sentry/fsimpl/host"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
@@ -84,15 +87,13 @@ type ExecArgs struct {
 	// the root group if not set explicitly.
 	KGID auth.KGID
 
-	// ExtraKGIDs is the list of additional groups to which the user
-	// belongs.
+	// ExtraKGIDs is the list of additional groups to which the user belongs.
 	ExtraKGIDs []auth.KGID
 
 	// Capabilities is the list of capabilities to give to the process.
 	Capabilities *auth.TaskCapabilities
 
-	// StdioIsPty indicates that FDs 0, 1, and 2 are connected to a host
-	// pty FD.
+	// StdioIsPty indicates that FDs 0, 1, and 2 are connected to a host pty FD.
 	StdioIsPty bool
 
 	// FilePayload determines the files to give to the new process.
@@ -117,7 +118,7 @@ func (args ExecArgs) String() string {
 
 // Exec runs a new task.
 func (proc *Proc) Exec(args *ExecArgs, waitStatus *uint32) error {
-	newTG, _, _, err := proc.execAsync(args)
+	newTG, _, _, _, err := proc.execAsync(args)
 	if err != nil {
 		return err
 	}
@@ -130,26 +131,18 @@ func (proc *Proc) Exec(args *ExecArgs, waitStatus *uint32) error {
 
 // ExecAsync runs a new task, but doesn't wait for it to finish. It is defined
 // as a function rather than a method to avoid exposing execAsync as an RPC.
-func ExecAsync(proc *Proc, args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadID, *host.TTYFileOperations, error) {
+func ExecAsync(proc *Proc, args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadID, *host.TTYFileOperations, *hostvfs2.TTYFileDescription, error) {
 	return proc.execAsync(args)
 }
 
 // execAsync runs a new task, but doesn't wait for it to finish. It returns the
 // newly created thread group and its PID. If the stdio FDs are TTYs, then a
 // TTYFileOperations that wraps the TTY is also returned.
-func (proc *Proc) execAsync(args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadID, *host.TTYFileOperations, error) {
+func (proc *Proc) execAsync(args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadID, *host.TTYFileOperations, *hostvfs2.TTYFileDescription, error) {
 	// Import file descriptors.
 	fdTable := proc.Kernel.NewFDTable()
 	defer fdTable.DecRef()
 
-	// No matter what happens, we should close all files in the FilePayload
-	// before returning. Any files that are imported will be duped.
-	defer func() {
-		for _, f := range args.FilePayload.Files {
-			f.Close()
-		}
-	}()
-
 	creds := auth.NewUserCredentials(
 		args.KUID,
 		args.KGID,
@@ -202,7 +195,7 @@ func (proc *Proc) execAsync(args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadI
 			vfsObj := proc.Kernel.VFS()
 			file, err := ResolveExecutablePath(ctx, vfsObj, initArgs.WorkingDirectory, initArgs.Argv[0], paths)
 			if err != nil {
-				return nil, 0, nil, fmt.Errorf("error finding executable %q in PATH %v: %v", initArgs.Argv[0], paths, err)
+				return nil, 0, nil, nil, fmt.Errorf("error finding executable %q in PATH %v: %v", initArgs.Argv[0], paths, err)
 			}
 			initArgs.File = fsbridge.NewVFSFile(file)
 		} else {
@@ -214,74 +207,57 @@ func (proc *Proc) execAsync(args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadI
 
 				// initArgs must hold a reference on MountNamespace, which will
 				// be donated to the new process in CreateProcess.
-				initArgs.MountNamespaceVFS2.IncRef()
+				initArgs.MountNamespace.IncRef()
 			}
 			f, err := initArgs.MountNamespace.ResolveExecutablePath(ctx, initArgs.WorkingDirectory, initArgs.Argv[0], paths)
 			if err != nil {
-				return nil, 0, nil, fmt.Errorf("error finding executable %q in PATH %v: %v", initArgs.Argv[0], paths, err)
+				return nil, 0, nil, nil, fmt.Errorf("error finding executable %q in PATH %v: %v", initArgs.Argv[0], paths, err)
 			}
 			initArgs.Filename = f
 		}
 	}
 
-	// TODO(gvisor.dev/issue/1623): Use host FD when supported in VFS2.
-	var ttyFile *fs.File
-	for appFD, hostFile := range args.FilePayload.Files {
-		var appFile *fs.File
-
-		if args.StdioIsPty && appFD < 3 {
-			// Import the file as a host TTY file.
-			if ttyFile == nil {
-				var err error
-				appFile, err = host.ImportFile(ctx, int(hostFile.Fd()), true /* isTTY */)
-				if err != nil {
-					return nil, 0, nil, err
-				}
-				defer appFile.DecRef()
-
-				// Remember this in the TTY file, as we will
-				// use it for the other stdio FDs.
-				ttyFile = appFile
-			} else {
-				// Re-use the existing TTY file, as all three
-				// stdio FDs must point to the same fs.File in
-				// order to share TTY state, specifically the
-				// foreground process group id.
-				appFile = ttyFile
-			}
-		} else {
-			// Import the file as a regular host file.
-			var err error
-			appFile, err = host.ImportFile(ctx, int(hostFile.Fd()), false /* isTTY */)
+	fds := make([]int, len(args.FilePayload.Files))
+	for i, file := range args.FilePayload.Files {
+		if kernel.VFS2Enabled {
+			// Need to dup to remove ownership from os.File.
+			dup, err := unix.Dup(int(file.Fd()))
 			if err != nil {
-				return nil, 0, nil, err
+				return nil, 0, nil, nil, fmt.Errorf("duplicating payload files: %w", err)
 			}
-			defer appFile.DecRef()
+			fds[i] = dup
+		} else {
+			// VFS1 dups the file on import.
+			fds[i] = int(file.Fd())
 		}
-
-		// Add the file to the FD map.
-		if err := fdTable.NewFDAt(ctx, int32(appFD), appFile, kernel.FDFlags{}); err != nil {
-			return nil, 0, nil, err
+	}
+	ttyFile, ttyFileVFS2, err := fdimport.Import(ctx, fdTable, args.StdioIsPty, fds)
+	if err != nil {
+		if kernel.VFS2Enabled {
+			for _, fd := range fds {
+				unix.Close(fd)
+			}
 		}
+		return nil, 0, nil, nil, err
 	}
 
 	tg, tid, err := proc.Kernel.CreateProcess(initArgs)
 	if err != nil {
-		return nil, 0, nil, err
+		return nil, 0, nil, nil, err
 	}
 
-	var ttyFileOps *host.TTYFileOperations
-	if ttyFile != nil {
-		// Set the foreground process group on the TTY before starting
-		// the process.
-		ttyFileOps = ttyFile.FileOperations.(*host.TTYFileOperations)
-		ttyFileOps.InitForegroundProcessGroup(tg.ProcessGroup())
+	// Set the foreground process group on the TTY before starting the process.
+	switch {
+	case ttyFile != nil:
+		ttyFile.InitForegroundProcessGroup(tg.ProcessGroup())
+	case ttyFileVFS2 != nil:
+		ttyFileVFS2.InitForegroundProcessGroup(tg.ProcessGroup())
 	}
 
 	// Start the newly created process.
 	proc.Kernel.StartProcess(tg)
 
-	return tg, tid, ttyFileOps, nil
+	return tg, tid, ttyFile, ttyFileVFS2, nil
 }
 
 // PsArgs is the set of arguments to ps.
diff --git a/pkg/sentry/fdimport/BUILD b/pkg/sentry/fdimport/BUILD
new file mode 100644
index 000000000..5e41ceb4e
--- /dev/null
+++ b/pkg/sentry/fdimport/BUILD
@@ -0,0 +1,19 @@
+load("//tools:defs.bzl", "go_library")
+
+package(licenses = ["notice"])
+
+go_library(
+    name = "fdimport",
+    srcs = [
+        "fdimport.go",
+    ],
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/context",
+        "//pkg/sentry/fs",
+        "//pkg/sentry/fs/host",
+        "//pkg/sentry/fsimpl/host",
+        "//pkg/sentry/kernel",
+        "//pkg/sentry/vfs",
+    ],
+)
diff --git a/pkg/sentry/fdimport/fdimport.go b/pkg/sentry/fdimport/fdimport.go
new file mode 100644
index 000000000..a4199f9e9
--- /dev/null
+++ b/pkg/sentry/fdimport/fdimport.go
@@ -0,0 +1,129 @@
+// 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 fdimport
+
+import (
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/fs/host"
+	hostvfs2 "gvisor.dev/gvisor/pkg/sentry/fsimpl/host"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+)
+
+// Import imports a slice of FDs into the given FDTable. If console is true,
+// sets up TTY for the first 3 FDs in the slice representing stdin, stdout,
+// stderr. Upon success, Import takes ownership of all FDs.
+func Import(ctx context.Context, fdTable *kernel.FDTable, console bool, fds []int) (*host.TTYFileOperations, *hostvfs2.TTYFileDescription, error) {
+	if kernel.VFS2Enabled {
+		ttyFile, err := importVFS2(ctx, fdTable, console, fds)
+		return nil, ttyFile, err
+	}
+	ttyFile, err := importFS(ctx, fdTable, console, fds)
+	return ttyFile, nil, err
+}
+
+func importFS(ctx context.Context, fdTable *kernel.FDTable, console bool, fds []int) (*host.TTYFileOperations, error) {
+	var ttyFile *fs.File
+	for appFD, hostFD := range fds {
+		var appFile *fs.File
+
+		if console && appFD < 3 {
+			// Import the file as a host TTY file.
+			if ttyFile == nil {
+				var err error
+				appFile, err = host.ImportFile(ctx, hostFD, true /* isTTY */)
+				if err != nil {
+					return nil, err
+				}
+				defer appFile.DecRef()
+
+				// Remember this in the TTY file, as we will
+				// use it for the other stdio FDs.
+				ttyFile = appFile
+			} else {
+				// Re-use the existing TTY file, as all three
+				// stdio FDs must point to the same fs.File in
+				// order to share TTY state, specifically the
+				// foreground process group id.
+				appFile = ttyFile
+			}
+		} else {
+			// Import the file as a regular host file.
+			var err error
+			appFile, err = host.ImportFile(ctx, hostFD, false /* isTTY */)
+			if err != nil {
+				return nil, err
+			}
+			defer appFile.DecRef()
+		}
+
+		// Add the file to the FD map.
+		if err := fdTable.NewFDAt(ctx, int32(appFD), appFile, kernel.FDFlags{}); err != nil {
+			return nil, err
+		}
+	}
+
+	if ttyFile == nil {
+		return nil, nil
+	}
+	return ttyFile.FileOperations.(*host.TTYFileOperations), nil
+}
+
+func importVFS2(ctx context.Context, fdTable *kernel.FDTable, console bool, stdioFDs []int) (*hostvfs2.TTYFileDescription, error) {
+	k := kernel.KernelFromContext(ctx)
+
+	var ttyFile *vfs.FileDescription
+	for appFD, hostFD := range stdioFDs {
+		var appFile *vfs.FileDescription
+
+		if console && appFD < 3 {
+			// Import the file as a host TTY file.
+			if ttyFile == nil {
+				var err error
+				appFile, err = hostvfs2.ImportFD(ctx, k.HostMount(), hostFD, true /* isTTY */)
+				if err != nil {
+					return nil, err
+				}
+				defer appFile.DecRef()
+
+				// Remember this in the TTY file, as we will use it for the other stdio
+				// FDs.
+				ttyFile = appFile
+			} else {
+				// Re-use the existing TTY file, as all three stdio FDs must point to
+				// the same fs.File in order to share TTY state, specifically the
+				// foreground process group id.
+				appFile = ttyFile
+			}
+		} else {
+			var err error
+			appFile, err = hostvfs2.ImportFD(ctx, k.HostMount(), hostFD, false /* isTTY */)
+			if err != nil {
+				return nil, err
+			}
+			defer appFile.DecRef()
+		}
+
+		if err := fdTable.NewFDAtVFS2(ctx, int32(appFD), appFile, kernel.FDFlags{}); err != nil {
+			return nil, err
+		}
+	}
+
+	if ttyFile == nil {
+		return nil, nil
+	}
+	return ttyFile.Impl().(*hostvfs2.TTYFileDescription), nil
+}
diff --git a/pkg/sentry/fsimpl/host/host.go b/pkg/sentry/fsimpl/host/host.go
index 34fbc69af..2be498afc 100644
--- a/pkg/sentry/fsimpl/host/host.go
+++ b/pkg/sentry/fsimpl/host/host.go
@@ -422,7 +422,7 @@ func (i *inode) open(ctx context.Context, d *vfs.Dentry, mnt *vfs.Mount) (*vfs.F
 	// TODO(gvisor.dev/issue/1672): Whitelist specific file types here, so that
 	// we don't allow importing arbitrary file types without proper support.
 	if i.isTTY {
-		fd := &ttyFD{
+		fd := &TTYFileDescription{
 			fileDescription: fileDescription{inode: i},
 			termios:         linux.DefaultSlaveTermios,
 		}
diff --git a/pkg/sentry/fsimpl/host/tty.go b/pkg/sentry/fsimpl/host/tty.go
index 8936afb06..68af6e5af 100644
--- a/pkg/sentry/fsimpl/host/tty.go
+++ b/pkg/sentry/fsimpl/host/tty.go
@@ -26,15 +26,15 @@ import (
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
-// ttyFD implements vfs.FileDescriptionImpl for a host file descriptor
-// that wraps a TTY FD.
-type ttyFD struct {
+// TTYFileDescription implements vfs.FileDescriptionImpl for a host file
+// descriptor that wraps a TTY FD.
+type TTYFileDescription struct {
 	fileDescription
 
 	// mu protects the fields below.
 	mu sync.Mutex `state:"nosave"`
 
-	// session is the session attached to this ttyFD.
+	// session is the session attached to this TTYFileDescription.
 	session *kernel.Session
 
 	// fgProcessGroup is the foreground process group that is currently
@@ -48,7 +48,7 @@ type ttyFD struct {
 // InitForegroundProcessGroup sets the foreground process group and session for
 // the TTY. This should only be called once, after the foreground process group
 // has been created, but before it has started running.
-func (t *ttyFD) InitForegroundProcessGroup(pg *kernel.ProcessGroup) {
+func (t *TTYFileDescription) InitForegroundProcessGroup(pg *kernel.ProcessGroup) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 	if t.fgProcessGroup != nil {
@@ -59,14 +59,14 @@ func (t *ttyFD) InitForegroundProcessGroup(pg *kernel.ProcessGroup) {
 }
 
 // ForegroundProcessGroup returns the foreground process for the TTY.
-func (t *ttyFD) ForegroundProcessGroup() *kernel.ProcessGroup {
+func (t *TTYFileDescription) ForegroundProcessGroup() *kernel.ProcessGroup {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 	return t.fgProcessGroup
 }
 
 // Release implements fs.FileOperations.Release.
-func (t *ttyFD) Release() {
+func (t *TTYFileDescription) Release() {
 	t.mu.Lock()
 	t.fgProcessGroup = nil
 	t.mu.Unlock()
@@ -78,7 +78,7 @@ func (t *ttyFD) Release() {
 //
 // Reading from a TTY is only allowed for foreground process groups. Background
 // process groups will either get EIO or a SIGTTIN.
-func (t *ttyFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
+func (t *TTYFileDescription) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 
@@ -96,7 +96,7 @@ func (t *ttyFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64,
 //
 // Reading from a TTY is only allowed for foreground process groups. Background
 // process groups will either get EIO or a SIGTTIN.
-func (t *ttyFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
+func (t *TTYFileDescription) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 
@@ -111,7 +111,7 @@ func (t *ttyFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadO
 }
 
 // PWrite implements vfs.FileDescriptionImpl.
-func (t *ttyFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
+func (t *TTYFileDescription) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 
@@ -126,7 +126,7 @@ func (t *ttyFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64
 }
 
 // Write implements vfs.FileDescriptionImpl.
-func (t *ttyFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
+func (t *TTYFileDescription) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 
@@ -141,7 +141,7 @@ func (t *ttyFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.Writ
 }
 
 // Ioctl implements vfs.FileDescriptionImpl.
-func (t *ttyFD) Ioctl(ctx context.Context, io usermem.IO, args arch.SyscallArguments) (uintptr, error) {
+func (t *TTYFileDescription) Ioctl(ctx context.Context, io usermem.IO, args arch.SyscallArguments) (uintptr, error) {
 	// Ignore arg[0]. This is the real FD:
 	fd := t.inode.hostFD
 	ioctl := args[1].Uint64()
@@ -321,7 +321,7 @@ func (t *ttyFD) Ioctl(ctx context.Context, io usermem.IO, args arch.SyscallArgum
 // is a bit convoluted, but documented inline.
 //
 // Preconditions: t.mu must be held.
-func (t *ttyFD) checkChange(ctx context.Context, sig linux.Signal) error {
+func (t *TTYFileDescription) checkChange(ctx context.Context, sig linux.Signal) error {
 	task := kernel.TaskFromContext(ctx)
 	if task == nil {
 		// No task? Linux does not have an analog for this case, but
diff --git a/pkg/sentry/vfs/context.go b/pkg/sentry/vfs/context.go
index 82781e6d3..c9e724fef 100644
--- a/pkg/sentry/vfs/context.go
+++ b/pkg/sentry/vfs/context.go
@@ -49,3 +49,27 @@ func RootFromContext(ctx context.Context) VirtualDentry {
 	}
 	return VirtualDentry{}
 }
+
+type rootContext struct {
+	context.Context
+	root VirtualDentry
+}
+
+// WithRoot returns a copy of ctx with the given root.
+func WithRoot(ctx context.Context, root VirtualDentry) context.Context {
+	return &rootContext{
+		Context: ctx,
+		root:    root,
+	}
+}
+
+// Value implements Context.Value.
+func (rc rootContext) Value(key interface{}) interface{} {
+	switch key {
+	case CtxRoot:
+		rc.root.IncRef()
+		return rc.root
+	default:
+		return rc.Context.Value(key)
+	}
+}
diff --git a/pkg/sentry/vfs/epoll.go b/pkg/sentry/vfs/epoll.go
index 8e0b40841..8297f964b 100644
--- a/pkg/sentry/vfs/epoll.go
+++ b/pkg/sentry/vfs/epoll.go
@@ -192,6 +192,7 @@ func (ep *EpollInstance) AddInterest(file *FileDescription, num int32, event lin
 		mask:     mask,
 		userData: event.Data,
 	}
+	epi.waiter.Callback = epi
 	ep.interest[key] = epi
 	wmask := waiter.EventMaskFromLinux(mask)
 	file.EventRegister(&epi.waiter, wmask)