Support sticky bit in vfs2.

Updates #2923.

PiperOrigin-RevId: 318648128

2 files changed, 13 insertions, 0 deletions

diff --git a/pkg/sentry/fsimpl/tmpfs/directory.go b/pkg/sentry/fsimpl/tmpfs/directory.go
index b172abc15..0a1ad4765 100644
--- a/pkg/sentry/fsimpl/tmpfs/directory.go
+++ b/pkg/sentry/fsimpl/tmpfs/directory.go
@@ -81,6 +81,10 @@ func (dir *directory) removeChildLocked(child *dentry) {
 	dir.iterMu.Unlock()
 }
 
+func (dir *directory) mayDelete(creds *auth.Credentials, child *dentry) error {
+	return vfs.CheckDeleteSticky(creds, linux.FileMode(atomic.LoadUint32(&dir.inode.mode)), auth.KUID(atomic.LoadUint32(&child.inode.uid)))
+}
+
 type directoryFD struct {
 	fileDescription
 	vfs.DirectoryFileDescriptionDefaultImpl
diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go
index f766b7ce2..71ac7b8e6 100644
--- a/pkg/sentry/fsimpl/tmpfs/filesystem.go
+++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go
@@ -492,6 +492,9 @@ func (fs *filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa
 	if !ok {
 		return syserror.ENOENT
 	}
+	if err := oldParentDir.mayDelete(rp.Credentials(), renamed); err != nil {
+		return err
+	}
 	// Note that we don't need to call rp.CheckMount(), since if renamed is a
 	// mount point then we want to rename the mount point, not anything in the
 	// mounted filesystem.
@@ -606,6 +609,9 @@ func (fs *filesystem) RmdirAt(ctx context.Context, rp *vfs.ResolvingPath) error
 	if !ok {
 		return syserror.ENOENT
 	}
+	if err := parentDir.mayDelete(rp.Credentials(), child); err != nil {
+		return err
+	}
 	childDir, ok := child.inode.impl.(*directory)
 	if !ok {
 		return syserror.ENOTDIR
@@ -716,6 +722,9 @@ func (fs *filesystem) UnlinkAt(ctx context.Context, rp *vfs.ResolvingPath) error
 	if !ok {
 		return syserror.ENOENT
 	}
+	if err := parentDir.mayDelete(rp.Credentials(), child); err != nil {
+		return err
+	}
 	if child.inode.isDir() {
 		return syserror.EISDIR
 	}