Close hostile recovery and concurrency gaps

crates/lazaret-core/src/configuration.rs

@@ -1597,7 +1597,10 @@ fn ensure_owned_directory(path: &Path, uid: u32) -> Result<PathBuf, Configuratio
     let mut current = open_absolute_directory(&existing_canonical)?;
     let mut canonical = existing_canonical;
     for component in missing.into_iter().rev() {
-        rustix::fs::mkdirat(&current, &component, Mode::RWXU).map_err(io_error)?;
+        match rustix::fs::mkdirat(&current, &component, Mode::RWXU) {
+            Ok(()) | Err(rustix::io::Errno::EXIST) => {}
+            Err(error) => return Err(io_error(error)),
+        }
         let next = openat2(
             &current,
             &component,

crates/lazaret-core/tests/configuration.rs

@@ -3,6 +3,7 @@ use std::fs;
 use std::os::unix::fs::{MetadataExt, PermissionsExt, symlink};
 use std::path::{Path, PathBuf};
 use std::sync::atomic::{AtomicU64, Ordering};
+use std::sync::{Arc, Barrier};
 
 use lazaret_core::codec::{CodecError, decode, encode};
 use lazaret_core::configuration::{
@@ -645,6 +646,31 @@ fn volume_symlinks_and_lazaret_owned_mode_drift_are_rejected() {
     );
 }
 
+#[test]
+fn concurrent_loaders_share_exact_owned_directory_creation() {
+    let tree = TestTree::new();
+    let config = write_configuration(&tree, &valid_configuration(&tree));
+    let barrier = Arc::new(Barrier::new(8));
+    std::thread::scope(|scope| {
+        let handles = (0..8)
+            .map(|_| {
+                let barrier = Arc::clone(&barrier);
+                let config = config.clone();
+                let tree = &tree;
+                scope.spawn(move || {
+                    let mut environment = BTreeMap::new();
+                    environment.insert("HOST_TOKEN".into(), "value".into());
+                    barrier.wait();
+                    load_trusted_configuration(request(tree, config, environment))
+                })
+            })
+            .collect::<Vec<_>>();
+        for handle in handles {
+            handle.join().unwrap().unwrap();
+        }
+    });
+}
+
 #[test]
 fn configuration_source_permissions_links_and_size_are_bounded() {
     for mutation in 0..3 {