1 files changed, 43 insertions, 56 deletions

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 01ca08804f51..284e2691e380 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -89,16 +89,28 @@ static bool klp_is_object_loaded(struct klp_object *obj)
 /* sets obj->mod if object is not vmlinux and module is found */
 static void klp_find_object_module(struct klp_object *obj)
 {
+        struct module *mod;
+
         if (!klp_is_module(obj))
                 return;
 
         mutex_lock(&module_mutex);
         /*
-         * We don't need to take a reference on the module here because we have
-         * the klp_mutex, which is also taken by the module notifier.  This
-         * prevents any module from unloading until we release the klp_mutex.
+         * We do not want to block removal of patched modules and therefore
+         * we do not take a reference here. The patches are removed by
+         * a going module handler instead.
+         */
+        mod = find_module(obj->name);
+        /*
+         * Do not mess work of the module coming and going notifiers.
+         * Note that the patch might still be needed before the going handler
+         * is called. Module functions can be called even in the GOING state
+         * until mod->exit() finishes. This is especially important for
+         * patches that modify semantic of the functions.
          */
-        obj->mod = find_module(obj->name);
+        if (mod && mod->klp_alive)
+                obj->mod = mod;
+
         mutex_unlock(&module_mutex);
 }
 
@@ -323,32 +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);
@@ -358,8 +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)
@@ -420,23 +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)
@@ -452,22 +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) &&
@@ -477,12 +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;
@@ -541,8 +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;
 
@@ -767,6 +748,7 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
                 return -EINVAL;
 
         obj->state = KLP_DISABLED;
+        obj->mod = NULL;
 
         klp_find_object_module(obj);
 
@@ -932,7 +914,6 @@ 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;
@@ -940,10 +921,7 @@ 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);
@@ -961,6 +939,15 @@ static int klp_module_notify(struct notifier_block *nb, unsigned long action,
 
         mutex_lock(&klp_mutex);
 
+        /*
+         * Each module has to know that the notifier has been called.
+         * We never know what module will get patched by a new patch.
+         */
+        if (action == MODULE_STATE_COMING)
+                mod->klp_alive = true;
+        else /* MODULE_STATE_GOING */
+                mod->klp_alive = false;
+
         list_for_each_entry(patch, &klp_patches, list) {
                 for (obj = patch->objs; obj->funcs; obj++) {
                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))