linux-kernel - Re: [PATCH v2 2/2] livepatch/module: remove livepatch module notifier

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Message-ID: <20160204095638.2834778c@gandalf.local.home>
Date:	Thu, 4 Feb 2016 09:56:38 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Petr Mladek <pmladek@...e.com>
Cc:	Jessica Yu <jeyu@...hat.com>, Josh Poimboeuf <jpoimboe@...hat.com>,
	Seth Jennings <sjenning@...hat.com>,
	Jiri Kosina <jikos@...nel.org>,
	Vojtech Pavlik <vojtech@...e.com>,
	Miroslav Benes <mbenes@...e.cz>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Ingo Molnar <mingo@...hat.com>, live-patching@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] livepatch/module: remove livepatch module
 notifier

On Thu, 4 Feb 2016 15:39:35 +0100
Petr Mladek <pmladek@...e.com> wrote:


> > @@ -3375,6 +3378,10 @@ static int complete_formation(struct module *mod, struct load_info *info)
> >  	mutex_unlock(&module_mutex);
> >  
> >  	ftrace_module_enable(mod);
> > +	err = klp_module_enable(mod);
> > +	if (err)
> > +		goto out;  
> 
> If you go out here, you need to revert some some operations
> that are normally done in the bug_cleanup: goto target
> in load_module(). In particular, you need to do:
> 
> 	/* module_bug_cleanup needs module_mutex protection */
> 	mutex_lock(&module_mutex);
> 	module_bug_cleanup(mod);
> 	mutex_unlock(&module_mutex);
> 
> 	ftrace_release_mod(mod);
> 
> 	/* we can't deallocate the module until we clear memory protection */
> 	module_disable_ro(mod);
> 	module_disable_nx(mod);
> 
> 
> IMHO, it would make sense to somehow split the complete_formation() function
> and avoid a code duplication in the error paths.

If complete_formation() fails, load_module will do a goto
ddebug_cleanup, which will eventually call ftrace_release_mod(). No
need to do it here.

-- Steve