Normalize inactive State Anchor work storage

crates/lazaret-state-anchor/src/lib.rs

@@ -33,10 +33,10 @@ use rustix::fs::{
 use rustix::io::dup;
 use rustix::thread::{ThreadNameSpaceType, move_into_thread_name_spaces};
 use storage::{
-    atomic_replace_at, create_directory, create_regular_file, descriptor_child_path,
-    descriptor_path, host_path, inspect_directory, move_all_entries, move_selected_entries,
-    open_directory, open_exact_directory_path, open_mounted_directory, open_or_create_quarantine,
-    open_regular_file, path_from_host, remove_directory_contents,
+    atomic_replace_at, clear_work_directory, create_directory, create_regular_file,
+    descriptor_child_path, descriptor_path, host_path, inspect_directory, move_all_entries,
+    move_selected_entries, open_directory, open_exact_directory_path, open_mounted_directory,
+    open_or_create_quarantine, open_regular_file, path_from_host, remove_directory_contents,
     require_directory_descriptor_identity, require_maintenance_work_shape, require_same_descriptor,
     validate_relative_path,
 };
@@ -272,6 +272,15 @@ impl<'configuration> StateAnchorLayout<'configuration> {
         self.revalidate()
     }
 
+    /// Clears the private fuse-overlayfs work directory after proving the anchor inactive.
+    ///
+    /// # Errors
+    /// Refuses changed authority, a remaining mount, or descriptor-confined cleanup failure.
+    pub fn normalize_inactive_work_directory(&self) -> Result<(), StateAnchorError> {
+        self.require_unmounted()?;
+        clear_work_directory(&self.work_descriptor)
+    }
+
     /// Atomically replaces sandbox runtime files in host-private transient storage.
     ///
     /// # Errors

crates/lazaret-state-anchor/src/lib/authority.rs

@@ -1,7 +1,8 @@
 use super::storage::{
-    descriptor_child_path, descriptor_path, inherit_for_exec, open_directory,
+    clear_work_directory, descriptor_child_path, descriptor_path, inherit_for_exec, open_directory,
     open_exact_directory_path, open_mounted_directory, overlay_options, path_from_host,
-    reopen_inherited_directory, require_directory_descriptor_identity, rootless_unmount_path,
+    reopen_inherited_directory, require_directory_descriptor_identity, require_same_descriptor,
+    rootless_unmount_path,
 };
 use super::{
     AsFd, AsRawFd, FileType, HostProcessOwnershipSlot, Instant, MOUNT_POLL_INTERVAL, MOUNT_TIMEOUT,
@@ -161,6 +162,7 @@ pub struct RuntimeStateAnchorAuthority {
     lower: OwnedFd,
     persistent_anchor: OwnedFd,
     upper: OwnedFd,
+    work: OwnedFd,
     runtime_anchor: OwnedFd,
     merged_label: PathBuf,
     merged_descriptor: OwnedFd,
@@ -233,13 +235,14 @@ impl RuntimeStateAnchorAuthority {
             inherited.runtime_anchor_label,
             (retained.st_dev, retained.st_ino),
         )?;
-        drop(open_directory(&persistent_anchor, Path::new("work"))?);
+        let work = open_directory(&persistent_anchor, Path::new("work"))?;
         let merged_descriptor = open_directory(&runtime_anchor, Path::new("merged"))?;
         let merged_label = inherited.runtime_anchor_label.join("merged");
         Ok(Self {
             lower,
             persistent_anchor,
             upper,
+            work,
             runtime_anchor,
             merged_label,
             merged_descriptor,
@@ -495,6 +498,9 @@ impl RuntimeStateAnchorMount {
             return Err(StateAnchorError::OwnershipMismatch);
         }
         child_broker().reap(process)?;
+        let observed_work = open_directory(&authority.persistent_anchor, Path::new("work"))?;
+        require_same_descriptor(&observed_work, &authority.work)?;
+        clear_work_directory(&authority.work)?;
         Ok(RuntimeStateAnchorAbsenceAuthority {
             runtime_anchor: authority.runtime_anchor,
             mount,

crates/lazaret-state-anchor/src/lib/mount.rs

@@ -151,6 +151,7 @@ impl<'layout, 'configuration> FuseOverlayfsMount<'layout, 'configuration> {
         }
         self.layout.require_unmounted()?;
         child_broker().reap(self.process)?;
+        self.layout.normalize_inactive_work_directory()?;
         Ok(())
     }
 
@@ -165,6 +166,7 @@ impl<'layout, 'configuration> FuseOverlayfsMount<'layout, 'configuration> {
         }
         self.layout.require_unmounted()?;
         child_broker().reap(self.process)?;
+        self.layout.normalize_inactive_work_directory()?;
         Ok(())
     }
 }

crates/lazaret-state-anchor/src/lib/storage.rs

@@ -6,6 +6,8 @@ use super::{
     mount_identity, openat2, renameat, renameat_with, statat, unlinkat,
 };
 
+const FUSE_OVERLAYFS_NESTED_WORK: &str = "work";
+
 /// Independently verifies that no mount is attached at the exact merged path.
 ///
 /// # Errors
@@ -240,18 +242,34 @@ pub(super) fn require_maintenance_work_shape(directory: impl AsFd) -> Result<(),
     if names.is_empty() {
         return Ok(());
     }
-    if names.as_slice() != [OsString::from("work")] {
+    if names.as_slice() != [OsString::from(FUSE_OVERLAYFS_NESTED_WORK)] {
         return Err(StateAnchorError::InvalidLayout(
             "State Anchor work directory has unsupported entries",
         ));
     }
-    let nested = open_directory(&directory, Path::new("work"))?;
+    let nested = open_directory(&directory, Path::new(FUSE_OVERLAYFS_NESTED_WORK))?;
+    require_nested_work_authority(&directory, &nested)?;
+    if directory_has_entries(&nested)? {
+        return Err(StateAnchorError::InvalidLayout(
+            "State Anchor work directory has unsupported entries",
+        ));
+    }
+    Ok(())
+}
+
+pub(super) fn clear_work_directory(directory: impl AsFd) -> Result<(), StateAnchorError> {
+    remove_directory_contents(directory)
+}
+
+fn require_nested_work_authority(
+    directory: impl AsFd,
+    nested: impl AsFd,
+) -> Result<(), StateAnchorError> {
     let parent = rustix::fs::fstat(&directory).map_err(io::Error::from)?;
     let child = rustix::fs::fstat(&nested).map_err(io::Error::from)?;
     if child.st_mode & 0o7777 != 0o700
         || child.st_uid != parent.st_uid
         || child.st_gid != parent.st_gid
-        || directory_has_entries(&nested)?
     {
         return Err(StateAnchorError::InvalidLayout(
             "State Anchor work directory has unsupported entries",

crates/lazaret-state-anchor/tests/authority.rs

@@ -18,6 +18,7 @@ use lazaret_state_anchor::{
     ProtectedRuntimeFiles, RuntimeStateAnchorAuthority, RuntimeStateAnchorInherited,
     StateAnchorLaunchAuthority, StateAnchorLayout, StateAnchorResetScope,
 };
+use rustix::fs::{XattrFlags, fsetxattr};
 
 static SEQUENCE: AtomicU64 = AtomicU64::new(0);
 
@@ -33,6 +34,40 @@ fn maintenance_accepts_exact_empty_fuse_overlayfs_work_shape() {
     layout.inspect_state().unwrap();
 }
 
+#[test]
+fn inactive_normalization_removes_exact_opaque_fuse_overlayfs_residue() {
+    let tree = TestTree::new();
+    let configuration = configuration(&tree);
+    let layout = StateAnchorLayout::create(&configuration).unwrap();
+    let nested = domain_path(&configuration).join("state-anchor/work/work");
+    fs::create_dir(&nested).unwrap();
+    fs::set_permissions(&nested, fs::Permissions::from_mode(0o700)).unwrap();
+    create_opaque_work_residue(&nested, "4");
+    create_opaque_work_residue(&nested, "12");
+
+    assert!(layout.inspect_state().is_err());
+    layout.normalize_inactive_work_directory().unwrap();
+    layout.inspect_state().unwrap();
+    let work = domain_path(&configuration).join("state-anchor/work");
+    assert!(work.read_dir().unwrap().next().is_none());
+}
+
+#[test]
+fn inactive_normalization_unlinks_work_symlinks_without_following_them() {
+    let tree = TestTree::new();
+    let configuration = configuration(&tree);
+    let layout = StateAnchorLayout::create(&configuration).unwrap();
+    let work = domain_path(&configuration).join("state-anchor/work");
+    let foreign = tree.path.join("foreign-work");
+    fs::create_dir(&foreign).unwrap();
+    fs::write(foreign.join("value"), b"foreign").unwrap();
+    std::os::unix::fs::symlink(&foreign, work.join("residue")).unwrap();
+
+    layout.normalize_inactive_work_directory().unwrap();
+    assert!(!work.join("residue").exists());
+    assert_eq!(fs::read(foreign.join("value")).unwrap(), b"foreign");
+}
+
 #[test]
 fn maintenance_refuses_mutated_fuse_overlayfs_work_shapes() {
     let tree = TestTree::new();
@@ -60,6 +95,26 @@ fn maintenance_refuses_mutated_fuse_overlayfs_work_shapes() {
     assert!(layout.inspect_state().is_err());
 }
 
+fn create_opaque_work_residue(nested: &Path, name: &str) {
+    let residue = nested.join(name);
+    fs::create_dir(&residue).unwrap();
+    fs::set_permissions(&residue, fs::Permissions::from_mode(0o755)).unwrap();
+    fs::write(residue.join(".wh..wh..opq"), b"").unwrap();
+    fs::set_permissions(
+        residue.join(".wh..wh..opq"),
+        fs::Permissions::from_mode(0o700),
+    )
+    .unwrap();
+    let residue = File::open(residue).unwrap();
+    fsetxattr(
+        &residue,
+        "user.fuseoverlayfs.opaque",
+        b"y",
+        XattrFlags::empty(),
+    )
+    .unwrap();
+}
+
 #[test]
 fn selected_reset_removes_exact_state_and_whiteout_without_touching_siblings() {
     let tree = TestTree::new();

crates/lazaret-state-anchor/tests/state-anchor-lifecycle.rs

@@ -1,6 +1,6 @@
 use std::collections::BTreeMap;
 use std::ffi::OsString;
-use std::fs;
+use std::fs::{self, File};
 use std::io::{self, BufRead, BufReader, Read, Write};
 use std::os::unix::ffi::OsStrExt;
 use std::os::unix::fs::MetadataExt;
@@ -157,10 +157,26 @@ fn run() -> io::Result<()> {
             "upper runtime-file entry survived transient override preflight",
         ));
     }
+    let held_directory = layout.merged().join("root/open-lock");
+    fs::create_dir_all(&held_directory)?;
+    let held = File::open(&held_directory)?;
+    fs::remove_dir(&held_directory)?;
+    drop(held);
+    if layout.work().join("work").read_dir()?.next().is_none() {
+        return Err(io::Error::other(
+            "open-directory removal did not create fuse-overlayfs work residue",
+        ));
+    }
     runtime_mount.unmount().map_err(io::Error::other)?;
+    layout.inspect_state().map_err(io::Error::other)?;
     fs::remove_file(layout.upper().join("etc/hosts"))?;
 
     let first = acquire(&layout, &artifact)?;
+    if layout.merged().join("root/open-lock").exists() {
+        return Err(io::Error::other(
+            "removed open directory returned after normalized remount",
+        ));
+    }
     fs::write(
         layout.merged().join("usr/bin/installed-tool"),
         b"persistent",