linux-kernel - Re: [PATCH] static_call: Handle module init failure correctly in static_call_del

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Message-ID: <Zuv0nmFblHUwuT8v@bombadil.infradead.org>
Date: Thu, 19 Sep 2024 02:53:34 -0700
From: Luis Chamberlain <mcgrof@...nel.org>
To: Christophe Leroy <christophe.leroy@...roup.eu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mike Rapoport <rppt@...nel.org>
Cc: Jinjie Ruan <ruanjinjie@...wei.com>, linux-kernel@...r.kernel.org,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Liu Shixin <liushixin2@...wei.com>
Subject: Re: [PATCH] static_call: Handle module init failure correctly in
 static_call_del_module()

On Fri, Sep 06, 2024 at 04:24:56PM -0700, Luis Chamberlain wrote:
> On Thu, Sep 05, 2024 at 11:44:00AM +0200, Thomas Gleixner wrote:
> > Now you at least provided the information that the missing cleanup in
> > the init() function is not the problem. So the obvious place to look is
> > in the module core code whether there is a failure path _after_
> > module->init() returned success.
> > 
> > do_init_module()
> >         ret = do_one_initcall(mod->init);
> >         ...
> > 	ret = module_enable_rodata_ro(mod, true);
> > 	if (ret)
> > 		goto fail_mutex_unlock;
> > 
> > and that error path does _not_ invoke module->exit(), which is obviously
> > not correct. Luis?
> 
> You're spot on this needs fixing.

Christophe, this is a regression caused by the second hunk of your commit
d1909c0221739 ("module: Don't ignore errors from set_memory_XX()") on v6.9.
Sadly there are a few issues with trying to get to call mod->exit():

- We should try try_stop_module()  and that can fail
- source_list may not be empty and that would block removal
- mod->exit may not exist

I'm wondering if instead we should try to do the module_enable_rodata_ro()
before the init, but that requires a bit more careful evaluation...

  Luis