[PATCH 2/2] livepatch: Clean up klp_init_object_loaded() when fails

[Petr Mladek]

When a module is loaded, klp_module_coming() iterates over patches and
calls klp_init_object_loaded(). If initialization fails, it delegates
cleanup to klp_cleanup_module_patches_limited().

However, the cleanup loop skips the failing patch. Each function called
in klp_init_object_loaded() is supposed to clean its own changes. This
works except for the changes done by klp_init_object_loaded().

The current code is a bit messy. The changes done by
klp_init_object_loaded() should get cleared by klp_free_object_loaded().
But this function also clears obj->mod which is set by
klp_module_coming(). And relocations are cleared separately.

Fix the situations by updating klp_free_object_loaded(). It should
revert all and only changes made by klp_init_object_loaded().
This requires some shuffling:

 + Clear obj->mod explicitly in klp_cleanup_module_patches_limited()
   and do not rely on klp_free_object_loaded().

 + Clear relocations in klp_free_object_loaded(). Remove the explicit
   call from klp_cleanup_module_patches_limited(). This requires
   adding the @patch parameter.

Finally, call klp_free_object_loaded() in the error path in
klp_init_object_loaded().

Reported-by: sashiko-bot@xxxxxxxxxx
Closes: https://lore.kernel.org/r/20260823062313.1321B1F000E9@xxxxxxxxxxxxxxx
Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
---
 kernel/livepatch/core.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index cdb25949f73b..1e59a3cc0895 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -725,18 +725,20 @@ static void __klp_free_funcs(struct klp_object *obj, bool nops_only)
 }
 
 /* Clean up when a patched object is unloaded */
-static void klp_free_object_loaded(struct klp_object *obj)
+static void klp_free_object_loaded(struct klp_patch *patch,
+				   struct klp_object *obj)
 {
 	struct klp_func *func;
 
-	obj->mod = NULL;
-
 	klp_for_each_func(obj, func) {
 		func->old_func = NULL;
 
 		if (func->nop)
 			func->new_func = NULL;
 	}
+
+	if (klp_is_module(obj))
+		klp_clear_object_relocs(patch, obj);
 }
 
 static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
@@ -875,7 +877,7 @@ static int klp_init_object_loaded(struct klp_patch *patch,
 		 */
 		ret = klp_apply_object_relocs(patch, obj);
 		if (ret)
-			return ret;
+			goto err;
 	}
 
 	klp_for_each_func(obj, func) {
@@ -883,7 +885,7 @@ static int klp_init_object_loaded(struct klp_patch *patch,
 					     func->old_sympos,
 					     (unsigned long *)&func->old_func);
 		if (ret)
-			return ret;
+			goto err;
 
 		/*
 		 * Aliased symbols share one address, so they would resolve to
@@ -896,7 +898,8 @@ static int klp_init_object_loaded(struct klp_patch *patch,
 			if (prev_func->old_func == func->old_func) {
 				pr_err("'%s' and '%s' resolve to the same address, aliased symbols are not supported\n",
 				       prev_func->old_name, func->old_name);
-				return -EINVAL;
+				ret = -EINVAL;
+				goto err;
 			}
 		}
 
@@ -905,7 +908,8 @@ static int klp_init_object_loaded(struct klp_patch *patch,
 		if (!ret) {
 			pr_err("kallsyms size lookup failed for '%s'\n",
 			       func->old_name);
-			return -ENOENT;
+			ret = -ENOENT;
+			goto err;
 		}
 
 		if (func->nop)
@@ -916,11 +920,17 @@ static int klp_init_object_loaded(struct klp_patch *patch,
 		if (!ret) {
 			pr_err("kallsyms size lookup failed for '%s' replacement\n",
 			       func->old_name);
-			return -ENOENT;
+			ret = -ENOENT;
+			goto err;
 		}
 	}
 
 	return 0;
+
+err:
+	klp_free_object_loaded(patch, obj);
+
+	return ret;
 }
 
 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
@@ -1274,8 +1284,8 @@ static void klp_cleanup_module_patches_limited(struct module *mod,
 			klp_unpatch_object(obj);
 
 			klp_post_unpatch_callback(obj);
-			klp_clear_object_relocs(patch, obj);
-			klp_free_object_loaded(obj);
+			klp_free_object_loaded(patch, obj);
+			obj->mod = NULL;
 			break;
 		}
 	}
-- 
2.55.0