linux-kernel - Re: [PATCH v12 07/12] livepatch: Use lists to manage patches, objects and functions

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Date:   Mon, 3 Sep 2018 18:00:45 +0200 (CEST)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Petr Mladek <pmladek@...e.com>
cc:     Jiri Kosina <jikos@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jason Baron <jbaron@...mai.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Jessica Yu <jeyu@...nel.org>,
        Evgenii Shatokhin <eshatokhin@...tuozzo.com>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v12 07/12] livepatch: Use lists to manage patches, objects
 and functions


> -#define klp_for_each_object(patch, obj) \
> +#define klp_for_each_object_static(patch, obj) \
>  	for (obj = patch->objs; obj->funcs || obj->name; obj++)
>  
> -#define klp_for_each_func(obj, func) \
> +#define klp_for_each_object(patch, obj)	\
> +	list_for_each_entry(obj, &patch->obj_list, node)
> +
> +#define klp_for_each_func_static(obj, func) \
>  	for (func = obj->funcs; \
>  	     func->old_name || func->new_addr || func->old_sympos; \
>  	     func++)
>  
> +#define klp_for_each_func(obj, func)	\
> +	list_for_each_entry(func, &obj->func_list, node)
> +
>  int klp_enable_patch(struct klp_patch *);
>  
>  void arch_klp_init_object_loaded(struct klp_patch *patch,
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index 6a47b36a6c9a..7bc23a106b5b 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -50,6 +50,21 @@ LIST_HEAD(klp_patches);
>  
>  static struct kobject *klp_root_kobj;
>  
> +static void klp_init_lists(struct klp_patch *patch)
> +{
> +	struct klp_object *obj;
> +	struct klp_func *func;
> +
> +	INIT_LIST_HEAD(&patch->obj_list);
> +	klp_for_each_object_static(patch, obj) {
> +		list_add(&obj->node, &patch->obj_list);
> +
> +		INIT_LIST_HEAD(&obj->func_list);
> +		klp_for_each_func_static(obj, func)
> +			list_add(&func->node, &obj->func_list);
> +	}
> +}
> +
>  static bool klp_is_module(struct klp_object *obj)
>  {
>  	return obj->name;
> @@ -664,6 +679,7 @@ static int klp_init_patch(struct klp_patch *patch)
>  	patch->module_put = false;
>  	INIT_LIST_HEAD(&patch->list);
>  	init_completion(&patch->finish);
> +	klp_init_lists(patch);

This could explode easily if patch->objs is NULL. The check is just below.
  
>  	if (!patch->objs)
>  		return -EINVAL;

Here.

klp_init_lists() calls klp_for_each_object_static() which accesses 
obj->name without a check for obj. One could argue that it is a 
responsibility of the user not to do such a silly thing, but since the 
check is already there, could you move klp_init_lists() call after the 
check?

Regards,
Miroslav