linux-kernel - Re: [PATCH v2 4/4] jump_label,module: Fix module lifetime for __jump_label_mod_text

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Message-ID: <20191023152932.217ef516@gandalf.local.home>
Date:   Wed, 23 Oct 2019 15:29:32 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.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, jpoimboe@...hat.com
Subject: Re: [PATCH v2 4/4] jump_label,module: Fix module lifetime for
 __jump_label_mod_text_reserved

On Mon, 07 Oct 2019 10:25:45 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> Nothing ensures the module exists while we're iterating
> mod->jump_entries in __jump_label_mod_text_reserved(), take a module
> reference to ensure the module sticks around.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve

> ---
>  kernel/jump_label.c |   10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> --- a/kernel/jump_label.c
> +++ b/kernel/jump_label.c
> @@ -539,19 +539,25 @@ static void static_key_set_mod(struct st
>  static int __jump_label_mod_text_reserved(void *start, void *end)
>  {
>  	struct module *mod;
> +	int ret;
>  
>  	preempt_disable();
>  	mod = __module_text_address((unsigned long)start);
>  	WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
> +	if (!try_module_get(mod))
> +		mod = NULL;
>  	preempt_enable();
>  
>  	if (!mod)
>  		return 0;
>  
> -
> -	return __jump_label_text_reserved(mod->jump_entries,
> +	ret = __jump_label_text_reserved(mod->jump_entries,
>  				mod->jump_entries + mod->num_jump_entries,
>  				start, end);
> +
> +	module_put(mod);
> +
> +	return ret;
>  }
>  
>  static void __jump_label_mod_update(struct static_key *key)
>