Enable SubprocessExited and SubprocessZombie for gVisor

Updates #164

PiperOrigin-RevId: 305544029

3 files changed, 78 insertions, 22 deletions

diff --git a/pkg/sentry/fs/proc/task.go b/pkg/sentry/fs/proc/task.go
index d6c5dd2c1..4d42eac83 100644
--- a/pkg/sentry/fs/proc/task.go
+++ b/pkg/sentry/fs/proc/task.go
@@ -57,6 +57,16 @@ func getTaskMM(t *kernel.Task) (*mm.MemoryManager, error) {
 	return m, nil
 }
 
+func checkTaskState(t *kernel.Task) error {
+	switch t.ExitState() {
+	case kernel.TaskExitZombie:
+		return syserror.EACCES
+	case kernel.TaskExitDead:
+		return syserror.ESRCH
+	}
+	return nil
+}
+
 // taskDir represents a task-level directory.
 //
 // +stateify savable
@@ -254,11 +264,12 @@ func newExe(t *kernel.Task, msrc *fs.MountSource) *fs.Inode {
 }
 
 func (e *exe) executable() (file fsbridge.File, err error) {
+	if err := checkTaskState(e.t); err != nil {
+		return nil, err
+	}
 	e.t.WithMuLocked(func(t *kernel.Task) {
 		mm := t.MemoryManager()
 		if mm == nil {
-			// TODO(b/34851096): Check shouldn't allow Readlink once the
-			// Task is zombied.
 			err = syserror.EACCES
 			return
 		}
@@ -268,7 +279,7 @@ func (e *exe) executable() (file fsbridge.File, err error) {
 		// (with locks held).
 		file = mm.Executable()
 		if file == nil {
-			err = syserror.ENOENT
+			err = syserror.ESRCH
 		}
 	})
 	return
@@ -313,11 +324,22 @@ func newNamespaceSymlink(t *kernel.Task, msrc *fs.MountSource, name string) *fs.
 	return newProcInode(t, n, msrc, fs.Symlink, t)
 }
 
+// Readlink reads the symlink value.
+func (n *namespaceSymlink) Readlink(ctx context.Context, inode *fs.Inode) (string, error) {
+	if err := checkTaskState(n.t); err != nil {
+		return "", err
+	}
+	return n.Symlink.Readlink(ctx, inode)
+}
+
 // Getlink implements fs.InodeOperations.Getlink.
 func (n *namespaceSymlink) Getlink(ctx context.Context, inode *fs.Inode) (*fs.Dirent, error) {
 	if !kernel.ContextCanTrace(ctx, n.t, false) {
 		return nil, syserror.EACCES
 	}
+	if err := checkTaskState(n.t); err != nil {
+		return nil, err
+	}
 
 	// Create a new regular file to fake the namespace file.
 	iops := fsutil.NewNoReadWriteFileInode(ctx, fs.RootOwner, fs.FilePermsFromMode(0777), linux.PROC_SUPER_MAGIC)
diff --git a/pkg/sentry/fsimpl/proc/task.go b/pkg/sentry/fsimpl/proc/task.go
index aee2a4392..888afc0fd 100644
--- a/pkg/sentry/fsimpl/proc/task.go
+++ b/pkg/sentry/fsimpl/proc/task.go
@@ -214,22 +214,6 @@ func newIO(t *kernel.Task, isThreadGroup bool) *ioData {
 	return &ioData{ioUsage: t}
 }
 
-func newNamespaceSymlink(task *kernel.Task, ino uint64, ns string) *kernfs.Dentry {
-	// Namespace symlinks should contain the namespace name and the inode number
-	// for the namespace instance, so for example user:[123456]. We currently fake
-	// the inode number by sticking the symlink inode in its place.
-	target := fmt.Sprintf("%s:[%d]", ns, ino)
-
-	inode := &kernfs.StaticSymlink{}
-	// Note: credentials are overridden by taskOwnedInode.
-	inode.Init(task.Credentials(), ino, target)
-
-	taskInode := &taskOwnedInode{Inode: inode, owner: task}
-	d := &kernfs.Dentry{}
-	d.Init(taskInode)
-	return d
-}
-
 // newCgroupData creates inode that shows cgroup information.
 // From man 7 cgroups: "For each cgroup hierarchy of which the process is a
 // member, there is one entry containing three colon-separated fields:
diff --git a/pkg/sentry/fsimpl/proc/task_files.go b/pkg/sentry/fsimpl/proc/task_files.go
index 88ea6a6d8..2c6f8bdfc 100644
--- a/pkg/sentry/fsimpl/proc/task_files.go
+++ b/pkg/sentry/fsimpl/proc/task_files.go
@@ -64,6 +64,16 @@ func getMMIncRef(task *kernel.Task) (*mm.MemoryManager, error) {
 	return m, nil
 }
 
+func checkTaskState(t *kernel.Task) error {
+	switch t.ExitState() {
+	case kernel.TaskExitZombie:
+		return syserror.EACCES
+	case kernel.TaskExitDead:
+		return syserror.ESRCH
+	}
+	return nil
+}
+
 type bufferWriter struct {
 	buf *bytes.Buffer
 }
@@ -628,11 +638,13 @@ func (s *exeSymlink) Getlink(ctx context.Context) (vfs.VirtualDentry, string, er
 }
 
 func (s *exeSymlink) executable() (file fsbridge.File, err error) {
+	if err := checkTaskState(s.task); err != nil {
+		return nil, err
+	}
+
 	s.task.WithMuLocked(func(t *kernel.Task) {
 		mm := t.MemoryManager()
 		if mm == nil {
-			// TODO(b/34851096): Check shouldn't allow Readlink once the
-			// Task is zombied.
 			err = syserror.EACCES
 			return
 		}
@@ -642,7 +654,7 @@ func (s *exeSymlink) executable() (file fsbridge.File, err error) {
 		// (with locks held).
 		file = mm.Executable()
 		if file == nil {
-			err = syserror.ENOENT
+			err = syserror.ESRCH
 		}
 	})
 	return
@@ -709,3 +721,41 @@ func (i *mountsData) Generate(ctx context.Context, buf *bytes.Buffer) error {
 	i.task.Kernel().VFS().GenerateProcMounts(ctx, rootDir, buf)
 	return nil
 }
+
+type namespaceSymlink struct {
+	kernfs.StaticSymlink
+
+	task *kernel.Task
+}
+
+func newNamespaceSymlink(task *kernel.Task, ino uint64, ns string) *kernfs.Dentry {
+	// Namespace symlinks should contain the namespace name and the inode number
+	// for the namespace instance, so for example user:[123456]. We currently fake
+	// the inode number by sticking the symlink inode in its place.
+	target := fmt.Sprintf("%s:[%d]", ns, ino)
+
+	inode := &namespaceSymlink{task: task}
+	// Note: credentials are overridden by taskOwnedInode.
+	inode.Init(task.Credentials(), ino, target)
+
+	taskInode := &taskOwnedInode{Inode: inode, owner: task}
+	d := &kernfs.Dentry{}
+	d.Init(taskInode)
+	return d
+}
+
+// Readlink implements Inode.
+func (s *namespaceSymlink) Readlink(ctx context.Context) (string, error) {
+	if err := checkTaskState(s.task); err != nil {
+		return "", err
+	}
+	return s.StaticSymlink.Readlink(ctx)
+}
+
+// Getlink implements Inode.Getlink.
+func (s *namespaceSymlink) Getlink(ctx context.Context) (vfs.VirtualDentry, string, error) {
+	if err := checkTaskState(s.task); err != nil {
+		return vfs.VirtualDentry{}, "", err
+	}
+	return s.StaticSymlink.Getlink(ctx)
+}