livepatch: Prevent patch inconsistencies if the coming module notifier fails

[deliverable/linux.git] / kernel / livepatch / core.c

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 3f9f1d6b4c2e5726217556a40454c46dbe368b89..c03c04637ec6d762aaee11574c9146d574090c6a 100644 (file)
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -128,7 +128,7 @@ static bool klp_is_patch_registered(struct klp_patch *patch)
 
 static bool klp_initialized(void)
 {
-       return klp_root_kobj;
+       return !!klp_root_kobj;
 }
 
 struct klp_find_arg {
@@ -335,32 +335,20 @@ unlock:
        rcu_read_unlock();
 }
 
-static int klp_disable_func(struct klp_func *func)
+static void klp_disable_func(struct klp_func *func)
 {
        struct klp_ops *ops;
-       int ret;
-
-       if (WARN_ON(func->state != KLP_ENABLED))
-               return -EINVAL;
 
-       if (WARN_ON(!func->old_addr))
-               return -EINVAL;
+       WARN_ON(func->state != KLP_ENABLED);
+       WARN_ON(!func->old_addr);
 
        ops = klp_find_ops(func->old_addr);
        if (WARN_ON(!ops))
-               return -EINVAL;
+               return;
 
        if (list_is_singular(&ops->func_stack)) {
-               ret = unregister_ftrace_function(&ops->fops);
-               if (ret) {
-                       pr_err("failed to unregister ftrace handler for function '%s' (%d)\n",
-                              func->old_name, ret);
-                       return ret;
-               }
-
-               ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
-               if (ret)
-                       pr_warn("function unregister succeeded but failed to clear the filter\n");
+               WARN_ON(unregister_ftrace_function(&ops->fops));
+               WARN_ON(ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0));
 
                list_del_rcu(&func->stack_node);
                list_del(&ops->node);
@@ -370,8 +358,6 @@ static int klp_disable_func(struct klp_func *func)
        }
 
        func->state = KLP_DISABLED;
-
-       return 0;
 }
 
 static int klp_enable_func(struct klp_func *func)
@@ -432,23 +418,15 @@ err:
        return ret;
 }
 
-static int klp_disable_object(struct klp_object *obj)
+static void klp_disable_object(struct klp_object *obj)
 {
        struct klp_func *func;
-       int ret;
-
-       for (func = obj->funcs; func->old_name; func++) {
-               if (func->state != KLP_ENABLED)
-                       continue;
 
-               ret = klp_disable_func(func);
-               if (ret)
-                       return ret;
-       }
+       for (func = obj->funcs; func->old_name; func++)
+               if (func->state == KLP_ENABLED)
+                       klp_disable_func(func);
 
        obj->state = KLP_DISABLED;
-
-       return 0;
 }
 
 static int klp_enable_object(struct klp_object *obj)
@@ -464,22 +442,19 @@ static int klp_enable_object(struct klp_object *obj)
 
        for (func = obj->funcs; func->old_name; func++) {
                ret = klp_enable_func(func);
-               if (ret)
-                       goto unregister;
+               if (ret) {
+                       klp_disable_object(obj);
+                       return ret;
+               }
        }
        obj->state = KLP_ENABLED;
 
        return 0;
-
-unregister:
-       WARN_ON(klp_disable_object(obj));
-       return ret;
 }
 
 static int __klp_disable_patch(struct klp_patch *patch)
 {
        struct klp_object *obj;
-       int ret;
 
        /* enforce stacking: only the last enabled patch can be disabled */
        if (!list_is_last(&patch->list, &klp_patches) &&
@@ -489,12 +464,8 @@ static int __klp_disable_patch(struct klp_patch *patch)
        pr_notice("disabling patch '%s'\n", patch->mod->name);
 
        for (obj = patch->objs; obj->funcs; obj++) {
-               if (obj->state != KLP_ENABLED)
-                       continue;
-
-               ret = klp_disable_object(obj);
-               if (ret)
-                       return ret;
+               if (obj->state == KLP_ENABLED)
+                       klp_disable_object(obj);
        }
 
        patch->state = KLP_DISABLED;
@@ -553,8 +524,6 @@ static int __klp_enable_patch(struct klp_patch *patch)
        pr_notice("enabling patch '%s'\n", patch->mod->name);
 
        for (obj = patch->objs; obj->funcs; obj++) {
-               klp_find_object_module(obj);
-
                if (!klp_is_object_loaded(obj))
                        continue;
 
@@ -914,7 +883,7 @@ int klp_register_patch(struct klp_patch *patch)
 }
 EXPORT_SYMBOL_GPL(klp_register_patch);
 
-static void klp_module_notify_coming(struct klp_patch *patch,
+static int klp_module_notify_coming(struct klp_patch *patch,
                                     struct klp_object *obj)
 {
        struct module *pmod = patch->mod;
@@ -922,22 +891,23 @@ static void klp_module_notify_coming(struct klp_patch *patch,
        int ret;
 
        ret = klp_init_object_loaded(patch, obj);
-       if (ret)
-               goto err;
+       if (ret) {
+               pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
+                       pmod->name, mod->name, ret);
+               return ret;
+       }
 
        if (patch->state == KLP_DISABLED)
-               return;
+               return 0;
 
        pr_notice("applying patch '%s' to loading module '%s'\n",
                  pmod->name, mod->name);
 
        ret = klp_enable_object(obj);
-       if (!ret)
-               return;
-
-err:
-       pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
-               pmod->name, mod->name, ret);
+       if (ret)
+               pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
+                       pmod->name, mod->name, ret);
+       return ret;
 }
 
 static void klp_module_notify_going(struct klp_patch *patch,
@@ -945,7 +915,6 @@ static void klp_module_notify_going(struct klp_patch *patch,
 {
        struct module *pmod = patch->mod;
        struct module *mod = obj->mod;
-       int ret;
 
        if (patch->state == KLP_DISABLED)
                goto disabled;
@@ -953,10 +922,7 @@ static void klp_module_notify_going(struct klp_patch *patch,
        pr_notice("reverting patch '%s' on unloading module '%s'\n",
                  pmod->name, mod->name);
 
-       ret = klp_disable_object(obj);
-       if (ret)
-               pr_warn("failed to revert patch '%s' on module '%s' (%d)\n",
-                       pmod->name, mod->name, ret);
+       klp_disable_object(obj);
 
 disabled:
        klp_free_object_loaded(obj);
@@ -965,6 +931,7 @@ disabled:
 static int klp_module_notify(struct notifier_block *nb, unsigned long action,
                             void *data)
 {
+       int ret;
        struct module *mod = data;
        struct klp_patch *patch;
        struct klp_object *obj;
@@ -990,7 +957,12 @@ static int klp_module_notify(struct notifier_block *nb, unsigned long action,
 
                        if (action == MODULE_STATE_COMING) {
                                obj->mod = mod;
-                               klp_module_notify_coming(patch, obj);
+                               ret = klp_module_notify_coming(patch, obj);
+                               if (ret) {
+                                       obj->mod = NULL;
+                                       pr_warn("patch '%s' is in an inconsistent state!\n",
+                                               patch->mod->name);
+                               }
                        } else /* MODULE_STATE_GOING */
                                klp_module_notify_going(patch, obj);