linux-kernel - Re: [PATCH v2] Moved module init-functions into the module.

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Date:   Thu, 22 Jun 2017 09:54:33 -0700
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     Steve Kemp <steve@...ve.fi>, linux-security-module@...r.kernel.org
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        James Morris <james.l.morris@...cle.com>,
        "Serge E. Hallyn" <serge@...lyn.com>
Subject: Re: [PATCH v2] Moved module init-functions into the module.

On 6/22/2017 1:45 AM, Steve Kemp wrote:
> This commit moves the call to initialize the LSM modules inline
> into the LSM-files themselves.
>
> This removes the need to hunt around for the setup, which was
> something that bit me when I wrote my own (unrelated) LSM.
>
> Keeping LSM code in one place, including the setup of the
> hooks seems like a sane choice.

The module initialization code belongs in the module.
The LSM infrastructure should have an absolute minimum
of module specific information. I would rather see the
"minor" modules (yama, loadpin) changed to use the module
registration scheme used by the "major" modules, but that
will require a mechanism to ensure module ordering, and
we don't have that yet. No, don't do this.

>
> This patch has been updated to use `security_init`, as per
> feedback from Ethan Zhao.  This should ensure that the
> LSM init is called "early".
>
> Signed-off-by: Steve Kemp <steve@...ve.fi>
> ---
>  include/linux/lsm_hooks.h  | 10 ----------
>  security/loadpin/loadpin.c |  5 ++++-
>  security/security.c        |  2 --
>  security/yama/yama_lsm.c   |  5 ++++-
>  4 files changed, 8 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 080f34e..a6dbdc7 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -1936,15 +1936,5 @@ static inline void security_delete_hooks(struct security_hook_list *hooks,
>  
>  extern int __init security_module_enable(const char *module);
>  extern void __init capability_add_hooks(void);
> -#ifdef CONFIG_SECURITY_YAMA
> -extern void __init yama_add_hooks(void);
> -#else
> -static inline void __init yama_add_hooks(void) { }
> -#endif
> -#ifdef CONFIG_SECURITY_LOADPIN
> -void __init loadpin_add_hooks(void);
> -#else
> -static inline void loadpin_add_hooks(void) { };
> -#endif
>  
>  #endif /* ! __LINUX_LSM_HOOKS_H */
> diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
> index dbe6efd..127eb5ca 100644
> --- a/security/loadpin/loadpin.c
> +++ b/security/loadpin/loadpin.c
> @@ -179,12 +179,15 @@ static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = {
>  	LSM_HOOK_INIT(kernel_read_file, loadpin_read_file),
>  };
>  
> -void __init loadpin_add_hooks(void)
> +static int __init loadpin_add_hooks(void)
>  {
>  	pr_info("ready to pin (currently %sabled)", enabled ? "en" : "dis");
>  	security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks), "loadpin");
> +	return 0;
>  }
>  
> +security_initcall(loadpin_add_hooks);
> +
>  /* Should not be mutable after boot, so not listed in sysfs (perm == 0). */
>  module_param(enabled, int, 0);
>  MODULE_PARM_DESC(enabled, "Pin module/firmware loading (default: true)");
> diff --git a/security/security.c b/security/security.c
> index b9fea39..110b85b 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -67,8 +67,6 @@ int __init security_init(void)
>  	 * Load minor LSMs, with the capability module always first.
>  	 */
>  	capability_add_hooks();
> -	yama_add_hooks();
> -	loadpin_add_hooks();
>  
>  	/*
>  	 * Load all the remaining security modules.
> diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
> index 8298e09..e3c1d10 100644
> --- a/security/yama/yama_lsm.c
> +++ b/security/yama/yama_lsm.c
> @@ -482,9 +482,12 @@ static void __init yama_init_sysctl(void)
>  static inline void yama_init_sysctl(void) { }
>  #endif /* CONFIG_SYSCTL */
>  
> -void __init yama_add_hooks(void)
> +static int __init yama_add_hooks(void)
>  {
>  	pr_info("Yama: becoming mindful.\n");
>  	security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks), "yama");
>  	yama_init_sysctl();
> +	return 0;
>  }
> +
> +security_initcall(yama_add_hooks);