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SubjectRe: [PATCH v12 07/12] livepatch: Use lists to manage patches, objects and functions
On Mon 2018-09-03 18:00:45, Miroslav Benes wrote:
>
> > -#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.

Great catch!

> since the check is already there, could you move klp_init_lists()
> call after the check?

The same problem is with accessing obj->funcs by
klp_for_each_func_static().

I have moved both checks into klp_init_lists(). I made sure that
the lists were initialized to be usable with the free functions
even in case of error.

Best Regards,
Petr

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