linux-kernel - Re: [PATCH v4 15/16] module: Move where we mark modules RO,X

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Date:   Mon, 21 Oct 2019 16:14:02 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, rostedt@...dmis.org,
        mhiramat@...nel.org, bristot@...hat.com, jbaron@...mai.com,
        torvalds@...ux-foundation.org, tglx@...utronix.de,
        mingo@...nel.org, namit@...are.com, hpa@...or.com, luto@...nel.org,
        ard.biesheuvel@...aro.org, jeyu@...nel.org
Subject: Re: [PATCH v4 15/16] module: Move where we mark modules RO,X

On Mon, Oct 21, 2019 at 08:53:12AM -0500, Josh Poimboeuf wrote:
> On Fri, Oct 18, 2019 at 09:35:40AM +0200, Peter Zijlstra wrote:
> > Now that set_all_modules_text_*() is gone, nothing depends on the
> > relation between ->state = COMING and the protection state anymore.
> > This enables moving the protection changes later, such that the COMING
> > notifier callbacks can more easily modify the text.
> > 
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > Cc: Jessica Yu <jeyu@...nel.org>
> > ---
> >  kernel/module.c |    8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > --- a/kernel/module.c
> > +++ b/kernel/module.c
> > @@ -3683,10 +3683,6 @@ static int complete_formation(struct mod
> >  	/* This relies on module_mutex for list integrity. */
> >  	module_bug_finalize(info->hdr, info->sechdrs, mod);
> >  
> > -	module_enable_ro(mod, false);
> > -	module_enable_nx(mod);
> > -	module_enable_x(mod);
> > -
> >  	/* Mark state as coming so strong_try_module_get() ignores us,
> >  	 * but kallsyms etc. can see us. */
> >  	mod->state = MODULE_STATE_COMING;
> > @@ -3852,6 +3848,10 @@ static int load_module(struct load_info
> >  	if (err)
> >  		goto bug_cleanup;
> >  
> > +	module_enable_ro(mod, false);
> > +	module_enable_nx(mod);
> > +	module_enable_x(mod);
> > +
> >  	/* Module is ready to execute: parsing args may do that. */
> >  	after_dashes = parse_args(mod->name, mod->args, mod->kp, mod->num_kp,
> >  				  -32768, 32767, mod,
> 
> [ Sorry if this was already discussed, I still have a large backlog. ]
> 
> Doesn't livepatch code also need to be modified?  We have:

Urgh bah.. I was too focussed on the other klp borkage :/ But yes,
arm64/ftrace and klp are the only two users of that function (outside of
module.c) and Mark was already writing a patch for arm64.

Means these last two patches need to wait a little until we've fixed
those.