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

Josh Poimboeuf
2015-05-13T14:14:28Z

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.

>
> 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.

--
Josh