linux-kernel - Re: [PATCH security-next v3 13/29] LoadPin: Rename "enable" to "enforce"

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Message-ID: <30e52d2d-844f-675f-8b12-b91ca5a8d96e@canonical.com>
Date:   Mon, 1 Oct 2018 14:17:35 -0700
From:   John Johansen <john.johansen@...onical.com>
To:     Kees Cook <keescook@...omium.org>, James Morris <jmorris@...ei.org>
Cc:     Casey Schaufler <casey@...aufler-ca.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        "Schaufler, Casey" <casey.schaufler@...el.com>,
        LSM <linux-security-module@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH security-next v3 13/29] LoadPin: Rename "enable" to
 "enforce"

On 09/24/2018 05:18 PM, Kees Cook wrote:
> LoadPin's "enable" setting is really about enforcement, not whether
> or not the LSM is using LSM hooks. Instead, split this out so that LSM
> enabling can be logically distinct from whether enforcement is happening
> (for example, the pinning happens when the LSM is enabled, but the pin
> is only checked when "enforce" is set). This allows LoadPin to continue
> to operate sanely in test environments once LSM enable/disable is
> centrally handled (i.e. we want LoadPin to be enabled separately from
> its enforcement).
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: John Johansen <john.johansen@...onical.com>

> ---
>  security/loadpin/Kconfig   |  4 ++--
>  security/loadpin/loadpin.c | 21 +++++++++++----------
>  2 files changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/security/loadpin/Kconfig b/security/loadpin/Kconfig
> index dd01aa91e521..8653608a3693 100644
> --- a/security/loadpin/Kconfig
> +++ b/security/loadpin/Kconfig
> @@ -10,10 +10,10 @@ config SECURITY_LOADPIN
>  	  have a root filesystem backed by a read-only device such as
>  	  dm-verity or a CDROM.
>  
> -config SECURITY_LOADPIN_ENABLED
> +config SECURITY_LOADPIN_ENFORCING
>  	bool "Enforce LoadPin at boot"
>  	depends on SECURITY_LOADPIN
>  	help
>  	  If selected, LoadPin will enforce pinning at boot. If not
>  	  selected, it can be enabled at boot with the kernel parameter
> -	  "loadpin.enabled=1".
> +	  "loadpin.enforcing=1".
> diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
> index 0716af28808a..d8a68a6f6fef 100644
> --- a/security/loadpin/loadpin.c
> +++ b/security/loadpin/loadpin.c
> @@ -44,7 +44,7 @@ static void report_load(const char *origin, struct file *file, char *operation)
>  	kfree(pathname);
>  }
>  
> -static int enabled = IS_ENABLED(CONFIG_SECURITY_LOADPIN_ENABLED);
> +static int enforcing = IS_ENABLED(CONFIG_SECURITY_LOADPIN_ENFORCING);
>  static struct super_block *pinned_root;
>  static DEFINE_SPINLOCK(pinned_root_spinlock);
>  
> @@ -60,8 +60,8 @@ static struct ctl_path loadpin_sysctl_path[] = {
>  
>  static struct ctl_table loadpin_sysctl_table[] = {
>  	{
> -		.procname       = "enabled",
> -		.data           = &enabled,
> +		.procname       = "enforcing",
> +		.data           = &enforcing,
>  		.maxlen         = sizeof(int),
>  		.mode           = 0644,
>  		.proc_handler   = proc_dointvec_minmax,
> @@ -97,7 +97,7 @@ static void check_pinning_enforcement(struct super_block *mnt_sb)
>  					   loadpin_sysctl_table))
>  			pr_notice("sysctl registration failed!\n");
>  		else
> -			pr_info("load pinning can be disabled.\n");
> +			pr_info("enforcement can be disabled.\n");
>  	} else
>  		pr_info("load pinning engaged.\n");
>  }
> @@ -128,7 +128,7 @@ static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
>  
>  	/* This handles the older init_module API that has a NULL file. */
>  	if (!file) {
> -		if (!enabled) {
> +		if (!enforcing) {
>  			report_load(origin, NULL, "old-api-pinning-ignored");
>  			return 0;
>  		}
> @@ -151,7 +151,7 @@ static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
>  		 * Unlock now since it's only pinned_root we care about.
>  		 * In the worst case, we will (correctly) report pinning
>  		 * failures before we have announced that pinning is
> -		 * enabled. This would be purely cosmetic.
> +		 * enforcing. This would be purely cosmetic.
>  		 */
>  		spin_unlock(&pinned_root_spinlock);
>  		check_pinning_enforcement(pinned_root);
> @@ -161,7 +161,7 @@ static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
>  	}
>  
>  	if (IS_ERR_OR_NULL(pinned_root) || load_root != pinned_root) {
> -		if (unlikely(!enabled)) {
> +		if (unlikely(!enforcing)) {
>  			report_load(origin, file, "pinning-ignored");
>  			return 0;
>  		}
> @@ -186,10 +186,11 @@ static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = {
>  
>  void __init loadpin_add_hooks(void)
>  {
> -	pr_info("ready to pin (currently %sabled)", enabled ? "en" : "dis");
> +	pr_info("ready to pin (currently %senforcing)\n",
> +		enforcing ? "" : "not ");
>  	security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks), "loadpin");
>  }
>  
>  /* 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)");
> +module_param(enforcing, int, 0);
> +MODULE_PARM_DESC(enforcing, "Enforce module/firmware pinning");
>