LSM: Separate idea of "major" LSM from "exclusive" LSM
In order to both support old "security=" Legacy Major LSM selection, and
handling real exclusivity, this creates LSM_FLAG_EXCLUSIVE and updates
the selection logic to handle them.
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index e28a3aa..c3843b3 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -2043,6 +2043,7 @@
char *lsm);
#define LSM_FLAG_LEGACY_MAJOR BIT(0)
+#define LSM_FLAG_EXCLUSIVE BIT(1)
struct lsm_info {
const char *name; /* Required. */
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index dfc5fbf..149a3e1 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -1723,7 +1723,7 @@
DEFINE_LSM(apparmor) = {
.name = "apparmor",
- .flags = LSM_FLAG_LEGACY_MAJOR,
+ .flags = LSM_FLAG_LEGACY_MAJOR | LSM_FLAG_EXCLUSIVE,
.enabled = &apparmor_enabled,
.init = apparmor_init,
};
diff --git a/security/security.c b/security/security.c
index 88de6b0..a8dd7de 100644
--- a/security/security.c
+++ b/security/security.c
@@ -49,6 +49,7 @@
/* Ordered list of LSMs to initialize. */
static __initdata struct lsm_info **ordered_lsms;
+static __initdata struct lsm_info *exclusive;
static __initdata bool debug;
#define init_debug(...) \
@@ -129,6 +130,12 @@
if (!is_enabled(lsm))
return false;
+ /* Not allowed if another exclusive LSM already initialized. */
+ if ((lsm->flags & LSM_FLAG_EXCLUSIVE) && exclusive) {
+ init_debug("exclusive disabled: %s\n", lsm->name);
+ return false;
+ }
+
return true;
}
@@ -144,6 +151,11 @@
if (enabled) {
int ret;
+ if ((lsm->flags & LSM_FLAG_EXCLUSIVE) && !exclusive) {
+ exclusive = lsm;
+ init_debug("exclusive chosen: %s\n", lsm->name);
+ }
+
init_debug("initializing %s\n", lsm->name);
ret = lsm->init();
WARN(ret, "%s failed to initialize: %d\n", lsm->name, ret);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 0f8ae2f..49865f1 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6989,7 +6989,7 @@
all processes and objects when they are created. */
DEFINE_LSM(selinux) = {
.name = "selinux",
- .flags = LSM_FLAG_LEGACY_MAJOR,
+ .flags = LSM_FLAG_LEGACY_MAJOR | LSM_FLAG_EXCLUSIVE,
.enabled = &selinux_enabled,
.init = selinux_init,
};
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 580e9d6..7807333 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4809,6 +4809,6 @@
*/
DEFINE_LSM(smack) = {
.name = "smack",
- .flags = LSM_FLAG_LEGACY_MAJOR,
+ .flags = LSM_FLAG_LEGACY_MAJOR | LSM_FLAG_EXCLUSIVE,
.init = smack_init,
};
diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
index a46f6bc..daff7d7 100644
--- a/security/tomoyo/tomoyo.c
+++ b/security/tomoyo/tomoyo.c
@@ -550,6 +550,6 @@
DEFINE_LSM(tomoyo) = {
.name = "tomoyo",
- .flags = LSM_FLAG_LEGACY_MAJOR,
+ .flags = LSM_FLAG_LEGACY_MAJOR | LSM_FLAG_EXCLUSIVE,
.init = tomoyo_init,
};