Re: [PATCH v3] livepatch: Prevent to apply the patch once coming module notifier fails

Minfei Huang
2015-05-14T01:31:10Z

On 05/13/15 at 09:14P, Josh Poimboeuf wrote:
> On Tue, May 12, 2015 at 10:04:44PM +0800, Minfei Huang wrote:
> > @@ -883,7 +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;
> > @@ -891,22 +891,24 @@ 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 the patch '%s' (%d)\n",
> > + pmod->name, ret);
> > + goto out;
> > + }
>
> Can you change it to:
>
> "failed to initialize the patch '%s' for module '%s' (%d)\n" ?
>
> That would make it more consistent with the other error message and
> identify the failing module.
>
> Also, the indentation should be fixed on the second pr_warn() line.
>

Will modify.

> >
> > if (patch->state == KLP_DISABLED)
> > - return;
> > + goto out;
> >
> > 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);
>
> Bad indentation here too.
>
> > @@ -930,6 +932,7 @@ 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;
> > @@ -955,7 +958,13 @@ 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 dead, remove it "
> > + "or re-install the module '%s'\n",
> > + patch->mod->name, obj->name);
> > + }
>
> The patch isn't necessarily dead, since it might also include previously
> enabled changes for vmlinux or other modules. It can actually be a
> dangerous condition if there's a mismatch between old code in the module
> and new code elsewhere. How about something like:
>
> "patch '%s' is in an inconsistent state!\n"
>
> Also, there's no need to split up the string literal into two lines.
> It's ok for a line to have more than 80 columns in that case.
>

Thanks for your reviewing. Will modify the patch.

Thanks
Minfei

> --
> Josh