On 10/1/18 5:54 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
ISTB: when "enforcing" is set). ??
> 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@xxxxxxxxxxxx>
> Reviewed-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
> Reviewed-by: John Johansen <john.johansen@xxxxxxxxxxxxx>
> ---
> 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");
>
--
~Randy
