Re: [PATCH v4 2/2] module: Introduce module unload taint tracking

From: Aaron Tomlin <atomlin@redhat.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "mcgrof@kernel.org" <mcgrof@kernel.org>,
	"cl@linux.com" <cl@linux.com>,
	"pmladek@suse.com" <pmladek@suse.com>,
	"mbenes@suse.cz" <mbenes@suse.cz>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-modules@vger.kernel.org" <linux-modules@vger.kernel.org>,
	"atomlin@atomlin.com" <atomlin@atomlin.com>,
	"ghalat@redhat.com" <ghalat@redhat.com>,
	"oleksandr@natalenko.name" <oleksandr@natalenko.name>,
	"neelx@redhat.com" <neelx@redhat.com>
Subject: Re: [PATCH v4 2/2] module: Introduce module unload taint tracking
Date: Mon, 2 May 2022 19:45:30 +0100	[thread overview]
Message-ID: <20220502184530.qjbl7rkilmxtmsgg@ava.usersys.com> (raw)
In-Reply-To: <73869e4f-7190-221c-897b-fc13ec54c8cb@csgroup.eu>

On Mon 2022-05-02 11:07 +0000, Christophe Leroy wrote:
> > @@ -150,6 +160,41 @@ int unregister_module_notifier(struct notifier_block *nb)
> >   }
> >   EXPORT_SYMBOL(unregister_module_notifier);
> >   
> > +#ifdef CONFIG_MODULE_UNLOAD_TAINT_TRACKING
> > +static int try_add_tainted_module(struct module *mod)
> > +{
> > +	struct mod_unload_taint *mod_taint;
> > +
> > +	module_assert_mutex_or_preempt();
> > +
> > +	list_for_each_entry_rcu(mod_taint, &unloaded_tainted_modules, list,
> > +				lockdep_is_held(&module_mutex)) {
> > +		size_t len = strlen(mod_taint->name);
> 
> Why do you need that strlen() at all, can't you just use strcmp() ?
> With strncmp() what happens if for instance mod_taint->name is "dead" 
> and mod->name is "deadbeef" ?

Hi Christophe,

Thanks for your feedback.

I see that. Furthermore, the length of a module's name is fixed.
Hence strcmp() should be fine.

Kind regards,

-- 
Aaron Tomlin