[PATCH 3/5] liveupdate: fail session restore on file deserialization errors

[Oskar Gerlicz Kowalczuk <oskar@gerlicz.space>]

luo_session_deserialize() calls luo_file_deserialize() but ignores its
return value. If file restore fails part-way through, the incoming
session still gets inserted and the caller still sees success.

Leaving a partially restored session on the incoming list is dangerous
because later retrieve or finish operations can walk half-built file
state and operate on uninitialized or stale entries.

Propagate file deserialization failures back to session restore,
remove the partially restored session, and free any struct luo_file
objects that were already allocated before returning the error.

Signed-off-by: Oskar Gerlicz Kowalczuk <oskar@gerlicz.space>
---
 kernel/liveupdate/luo_file.c    | 45 ++++++++++++++++++++-------------
 kernel/liveupdate/luo_session.c | 27 +++++++-------------
 2 files changed, 36 insertions(+), 36 deletions(-)

diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
index 5acee4174bf0..cc0fd7e9c332 100644
--- a/kernel/liveupdate/luo_file.c
+++ b/kernel/liveupdate/luo_file.c
@@ -717,6 +717,22 @@ int luo_file_finish(struct luo_file_set *file_set)
 	return 0;
 }
 
+static void luo_file_discard_deserialized(struct luo_file_set *file_set)
+{
+	struct luo_file *luo_file;
+
+	while (!list_empty(&file_set->files_list)) {
+		luo_file = list_last_entry(&file_set->files_list,
+					   struct luo_file, list);
+		list_del(&luo_file->list);
+		mutex_destroy(&luo_file->mutex);
+		kfree(luo_file);
+	}
+
+	file_set->count = 0;
+	file_set->files = NULL;
+}
+
 /**
  * luo_file_deserialize - Reconstructs the list of preserved files in the new kernel.
  * @file_set:     The incoming file_set to fill with deserialized data.
@@ -747,6 +763,7 @@ int luo_file_deserialize(struct luo_file_set *file_set,
 {
 	struct luo_file_ser *file_ser;
 	u64 i;
+	int err;
 
 	if (!file_set_ser->files) {
 		WARN_ON(file_set_ser->count);
@@ -756,21 +773,6 @@ int luo_file_deserialize(struct luo_file_set *file_set,
 	file_set->count = file_set_ser->count;
 	file_set->files = phys_to_virt(file_set_ser->files);
 
-	/*
-	 * Note on error handling:
-	 *
-	 * If deserialization fails (e.g., allocation failure or corrupt data),
-	 * we intentionally skip cleanup of files that were already restored.
-	 *
-	 * A partial failure leaves the preserved state inconsistent.
-	 * Implementing a safe "undo" to unwind complex dependencies (sessions,
-	 * files, hardware state) is error-prone and provides little value, as
-	 * the system is effectively in a broken state.
-	 *
-	 * We treat these resources as leaked. The expected recovery path is for
-	 * userspace to detect the failure and trigger a reboot, which will
-	 * reliably reset devices and reclaim memory.
-	 */
 	file_ser = file_set->files;
 	for (i = 0; i < file_set->count; i++) {
 		struct liveupdate_file_handler *fh;
@@ -787,12 +789,15 @@ int luo_file_deserialize(struct luo_file_set *file_set,
 		if (!handler_found) {
 			pr_warn("No registered handler for compatible '%s'\n",
 				file_ser[i].compatible);
-			return -ENOENT;
+			err = -ENOENT;
+			goto err_discard;
 		}
 
 		luo_file = kzalloc_obj(*luo_file);
-		if (!luo_file)
-			return -ENOMEM;
+		if (!luo_file) {
+			err = -ENOMEM;
+			goto err_discard;
+		}
 
 		luo_file->fh = fh;
 		luo_file->file = NULL;
@@ -803,6 +808,10 @@ int luo_file_deserialize(struct luo_file_set *file_set,
 	}
 
 	return 0;
+
+err_discard:
+	luo_file_discard_deserialized(file_set);
+	return err;
 }
 
 void luo_file_set_init(struct luo_file_set *file_set)
diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
index 39215e5eda7a..77afa913d6c7 100644
--- a/kernel/liveupdate/luo_session.c
+++ b/kernel/liveupdate/luo_session.c
@@ -565,21 +565,6 @@ int luo_session_deserialize(void)
 	if (!sh->active)
 		return 0;
 
-	/*
-	 * Note on error handling:
-	 *
-	 * If deserialization fails (e.g., allocation failure or corrupt data),
-	 * we intentionally skip cleanup of sessions that were already restored.
-	 *
-	 * A partial failure leaves the preserved state inconsistent.
-	 * Implementing a safe "undo" to unwind complex dependencies (sessions,
-	 * files, hardware state) is error-prone and provides little value, as
-	 * the system is effectively in a broken state.
-	 *
-	 * We treat these resources as leaked. The expected recovery path is for
-	 * userspace to detect the failure and trigger a reboot, which will
-	 * reliably reset devices and reclaim memory.
-	 */
 	for (int i = 0; i < sh->header_ser->count; i++) {
 		struct luo_session *session;
 
@@ -598,9 +583,15 @@ int luo_session_deserialize(void)
 			return err;
 		}
 
-		scoped_guard(mutex, &session->mutex) {
-			luo_file_deserialize(&session->file_set,
-					     &sh->ser[i].file_set_ser);
+		scoped_guard(mutex, &session->mutex)
+			err = luo_file_deserialize(&session->file_set,
+						   &sh->ser[i].file_set_ser);
+		if (err) {
+			pr_warn("Failed to deserialize session [%s] files %pe\n",
+				session->name, ERR_PTR(err));
+			luo_session_remove(sh, session);
+			luo_session_free(session);
+			return err;
 		}
 	}
 
-- 
2.53.0