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LoadPin: Rename boot param "enabled" to "enforce"

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LoadPin's "enabled" 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@chromium.org>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
This commit is contained in:
Kees Cook 2018-09-24 14:43:59 -07:00
parent f4b626d6de
commit 13523bef1e
2 changed files with 13 additions and 12 deletions
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4
security/loadpin/Kconfig
View File

@ -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_ENFORCE
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.enforce=1".

21
security/loadpin/loadpin.c
View File

@ -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 enforce = IS_ENABLED(CONFIG_SECURITY_LOADPIN_ENFORCE);
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 = "enforce",
.data = &enforce,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
@ -100,7 +100,7 @@ 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");
}
@ -131,7 +131,7 @@ 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 (!enforce) {
report_load(origin, NULL, "old-api-pinning-ignored");
return 0;
}
@ -154,7 +154,7 @@ 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);
@ -164,7 +164,7 @@ 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(!enforce)) {
report_load(origin, file, "pinning-ignored");
return 0;
}
@ -189,10 +189,11 @@ 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",
enforce ? "" : "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(enforce, int, 0);
MODULE_PARM_DESC(enforce, "Enforce module/firmware pinning");