linux-kernel - Re: [RFC PATCH 2/2] module: When modifying a module's text ignore modules which are going away too

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Message-ID: <87d1in538x.fsf@rustcorp.com.au>
Date:   Wed, 26 Oct 2016 11:35:18 +1030
From:   Rusty Russell <rusty@...tcorp.com.au>
To:     Aaron Tomlin <atomlin@...hat.com>, linux-kernel@...r.kernel.org
Cc:     rostedt@...dmis.org
Subject: Re: [RFC PATCH 2/2] module: When modifying a module's text ignore modules which are going away too

Aaron Tomlin <atomlin@...hat.com> writes:
> By default, during the access permission modification of a module's core
> and init pages, we only ignore modules that are malformed. There is no
> reason not to extend this to modules which are going away too.

Well, it depends on all the callers (ie. ftrace): is that also ignoring
modules which are going away?

Otherwise, we set MODULE_STATE_GOING, ftrace walks all the modules and
this one is still RO...

Thanks,
Rusty.

> This patch makes both set_all_modules_text_rw() and
> set_all_modules_text_ro() skip modules which are going away too.
>
> Signed-off-by: Aaron Tomlin <atomlin@...hat.com>
> ---
>  kernel/module.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/module.c b/kernel/module.c
> index ff93ab8..09c386b 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -1953,7 +1953,8 @@ void set_all_modules_text_rw(void)
>  
>  	mutex_lock(&module_mutex);
>  	list_for_each_entry_rcu(mod, &modules, list) {
> -		if (mod->state == MODULE_STATE_UNFORMED)
> +		if (mod->state == MODULE_STATE_UNFORMED ||
> +			mod->state == MODULE_STATE_GOING)
>  			continue;
>  
>  		frob_text(&mod->core_layout, set_memory_rw);
> @@ -1969,7 +1970,8 @@ void set_all_modules_text_ro(void)
>  
>  	mutex_lock(&module_mutex);
>  	list_for_each_entry_rcu(mod, &modules, list) {
> -		if (mod->state == MODULE_STATE_UNFORMED)
> +		if (mod->state == MODULE_STATE_UNFORMED ||
> +			mod->state == MODULE_STATE_GOING)
>  			continue;
>  
>  		frob_text(&mod->core_layout, set_memory_ro);
> -- 
> 2.5.5