1 files changed, 45 insertions, 3 deletions

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index ecb7660f1d8b..113645ee86b6 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -611,11 +611,16 @@ static struct kobj_type klp_ktype_func = {
 	.sysfs_ops = &kobj_sysfs_ops,
 };
 
-static void klp_free_funcs(struct klp_object *obj)
+static void __klp_free_funcs(struct klp_object *obj, bool nops_only)
 {
 	struct klp_func *func, *tmp_func;
 
 	klp_for_each_func_safe(obj, func, tmp_func) {
+		if (nops_only && !func->nop)
+			continue;
+
+		list_del(&func->node);
+
 		/* Might be called from klp_init_patch() error path. */
 		if (func->kobj_added) {
 			kobject_put(&func->kobj);
@@ -640,12 +645,17 @@ static void klp_free_object_loaded(struct klp_object *obj)
 	}
 }
 
-static void klp_free_objects(struct klp_patch *patch)
+static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
 {
 	struct klp_object *obj, *tmp_obj;
 
 	klp_for_each_object_safe(patch, obj, tmp_obj) {
-		klp_free_funcs(obj);
+		__klp_free_funcs(obj, nops_only);
+
+		if (nops_only && !obj->dynamic)
+			continue;
+
+		list_del(&obj->node);
 
 		/* Might be called from klp_init_patch() error path. */
 		if (obj->kobj_added) {
@@ -656,6 +666,16 @@ static void klp_free_objects(struct klp_patch *patch)
 	}
 }
 
+static void klp_free_objects(struct klp_patch *patch)
+{
+	__klp_free_objects(patch, false);
+}
+
+static void klp_free_objects_dynamic(struct klp_patch *patch)
+{
+	__klp_free_objects(patch, true);
+}
+
 /*
  * This function implements the free operations that can be called safely
  * under klp_mutex.
@@ -1085,6 +1105,28 @@ void klp_discard_replaced_patches(struct klp_patch *new_patch)
 }
 
 /*
+ * This function removes the dynamically allocated 'nop' functions.
+ *
+ * We could be pretty aggressive. NOPs do not change the existing
+ * behavior except for adding unnecessary delay by the ftrace handler.
+ *
+ * It is safe even when the transition was forced. The ftrace handler
+ * will see a valid ops->func_stack entry thanks to RCU.
+ *
+ * We could even free the NOPs structures. They must be the last entry
+ * in ops->func_stack. Therefore unregister_ftrace_function() is called.
+ * It does the same as klp_synchronize_transition() to make sure that
+ * nobody is inside the ftrace handler once the operation finishes.
+ *
+ * IMPORTANT: It must be called right after removing the replaced patches!
+ */
+void klp_discard_nops(struct klp_patch *new_patch)
+{
+	klp_unpatch_objects_dynamic(klp_transition_patch);
+	klp_free_objects_dynamic(klp_transition_patch);
+}
+
+/*
  * Remove parts of patches that touch a given kernel module. The list of
  * patches processed might be limited. When limit is NULL, all patches
  * will be handled.