diff options
| -rw-r--r-- | include/linux/livepatch.h | 6 | ||||
| -rw-r--r-- | kernel/livepatch/core.c | 137 |
2 files changed, 98 insertions, 45 deletions
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index 634e13876380..6978785bc059 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h @@ -45,6 +45,7 @@ * @stack_node: list node for klp_ops func_stack list * @old_size: size of the old function * @new_size: size of the new function + * @kobj_added: @kobj has been added and needs freeing * @patched: the func has been added to the klp_ops list * @transition: the func is currently being applied or reverted * @@ -81,6 +82,7 @@ struct klp_func { struct kobject kobj; struct list_head stack_node; unsigned long old_size, new_size; + bool kobj_added; bool patched; bool transition; }; @@ -117,6 +119,7 @@ struct klp_callbacks { * @kobj: kobject for sysfs resources * @mod: kernel module associated with the patched object * (NULL for vmlinux) + * @kobj_added: @kobj has been added and needs freeing * @patched: the object's funcs have been added to the klp_ops list */ struct klp_object { @@ -128,6 +131,7 @@ struct klp_object { /* internal */ struct kobject kobj; struct module *mod; + bool kobj_added; bool patched; }; @@ -137,6 +141,7 @@ struct klp_object { * @objs: object entries for kernel objects to be patched * @list: list node for global list of registered patches * @kobj: kobject for sysfs resources + * @kobj_added: @kobj has been added and needs freeing * @enabled: the patch is enabled (but operation may be incomplete) * @finish: for waiting till it is safe to remove the patch module */ @@ -148,6 +153,7 @@ struct klp_patch { /* internal */ struct list_head list; struct kobject kobj; + bool kobj_added; bool enabled; struct completion finish; }; diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 20589da35194..6f0d9095f662 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -465,17 +465,15 @@ static struct kobj_type klp_ktype_func = { .sysfs_ops = &kobj_sysfs_ops, }; -/* - * Free all functions' kobjects in the array up to some limit. When limit is - * NULL, all kobjects are freed. - */ -static void klp_free_funcs_limited(struct klp_object *obj, - struct klp_func *limit) +static void klp_free_funcs(struct klp_object *obj) { struct klp_func *func; - for (func = obj->funcs; func->old_name && func != limit; func++) - kobject_put(&func->kobj); + klp_for_each_func(obj, func) { + /* Might be called from klp_init_patch() error path. */ + if (func->kobj_added) + kobject_put(&func->kobj); + } } /* Clean up when a patched object is unloaded */ @@ -489,30 +487,60 @@ static void klp_free_object_loaded(struct klp_object *obj) func->old_func = NULL; } -/* - * Free all objects' kobjects in the array up to some limit. When limit is - * NULL, all kobjects are freed. - */ -static void klp_free_objects_limited(struct klp_patch *patch, - struct klp_object *limit) +static void klp_free_objects(struct klp_patch *patch) { struct klp_object *obj; - for (obj = patch->objs; obj->funcs && obj != limit; obj++) { - klp_free_funcs_limited(obj, NULL); - kobject_put(&obj->kobj); + klp_for_each_object(patch, obj) { + klp_free_funcs(obj); + + /* Might be called from klp_init_patch() error path. */ + if (obj->kobj_added) + kobject_put(&obj->kobj); } } -static void klp_free_patch(struct klp_patch *patch) +/* + * This function implements the free operations that can be called safely + * under klp_mutex. + * + * The operation must be completed by calling klp_free_patch_finish() + * outside klp_mutex. + */ +static void klp_free_patch_start(struct klp_patch *patch) { - klp_free_objects_limited(patch, NULL); if (!list_empty(&patch->list)) list_del(&patch->list); + + klp_free_objects(patch); +} + +/* + * This function implements the free part that must be called outside + * klp_mutex. + * + * It must be called after klp_free_patch_start(). And it has to be + * the last function accessing the livepatch structures when the patch + * gets disabled. + */ +static void klp_free_patch_finish(struct klp_patch *patch) +{ + /* + * Avoid deadlock with enabled_store() sysfs callback by + * calling this outside klp_mutex. It is safe because + * this is called when the patch gets disabled and it + * cannot get enabled again. + */ + if (patch->kobj_added) { + kobject_put(&patch->kobj); + wait_for_completion(&patch->finish); + } } static int klp_init_func(struct klp_object *obj, struct klp_func *func) { + int ret; + if (!func->old_name || !func->new_func) return -EINVAL; @@ -528,9 +556,13 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func) * object. If the user selects 0 for old_sympos, then 1 will be used * since a unique symbol will be the first occurrence. */ - return kobject_init_and_add(&func->kobj, &klp_ktype_func, - &obj->kobj, "%s,%lu", func->old_name, - func->old_sympos ? func->old_sympos : 1); + ret = kobject_init_and_add(&func->kobj, &klp_ktype_func, + &obj->kobj, "%s,%lu", func->old_name, + func->old_sympos ? func->old_sympos : 1); + if (!ret) + func->kobj_added = true; + + return ret; } /* Arches may override this to finish any remaining arch-specific tasks */ @@ -589,9 +621,6 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj) int ret; const char *name; - if (!obj->funcs) - return -EINVAL; - if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN) return -EINVAL; @@ -605,46 +634,66 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj) &patch->kobj, "%s", name); if (ret) return ret; + obj->kobj_added = true; klp_for_each_func(obj, func) { ret = klp_init_func(obj, func); if (ret) - goto free; + return ret; } - if (klp_is_object_loaded(obj)) { + if (klp_is_object_loaded(obj)) ret = klp_init_object_loaded(patch, obj); - if (ret) - goto free; - } - - return 0; -free: - klp_free_funcs_limited(obj, func); - kobject_put(&obj->kobj); return ret; } -static int klp_init_patch(struct klp_patch *patch) +static int klp_init_patch_early(struct klp_patch *patch) { struct klp_object *obj; - int ret; + struct klp_func *func; if (!patch->objs) return -EINVAL; - mutex_lock(&klp_mutex); - + INIT_LIST_HEAD(&patch->list); + patch->kobj_added = false; patch->enabled = false; init_completion(&patch->finish); + klp_for_each_object(patch, obj) { + if (!obj->funcs) + return -EINVAL; + + obj->kobj_added = false; + + klp_for_each_func(obj, func) + func->kobj_added = false; + } + + return 0; +} + +static int klp_init_patch(struct klp_patch *patch) +{ + struct klp_object *obj; + int ret; + + mutex_lock(&klp_mutex); + + ret = klp_init_patch_early(patch); + if (ret) { + mutex_unlock(&klp_mutex); + return ret; + } + ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch, klp_root_kobj, "%s", patch->mod->name); if (ret) { mutex_unlock(&klp_mutex); return ret; } + patch->kobj_added = true; klp_for_each_object(patch, obj) { ret = klp_init_object(patch, obj); @@ -659,12 +708,11 @@ static int klp_init_patch(struct klp_patch *patch) return 0; free: - klp_free_objects_limited(patch, obj); + klp_free_patch_start(patch); mutex_unlock(&klp_mutex); - kobject_put(&patch->kobj); - wait_for_completion(&patch->finish); + klp_free_patch_finish(patch); return ret; } @@ -693,12 +741,11 @@ int klp_unregister_patch(struct klp_patch *patch) goto err; } - klp_free_patch(patch); + klp_free_patch_start(patch); mutex_unlock(&klp_mutex); - kobject_put(&patch->kobj); - wait_for_completion(&patch->finish); + klp_free_patch_finish(patch); return 0; err: |