linux-kernel - [RFC PATCH 15/15] LSM: Remove exclusive LSM flag

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Message-ID: <20250621171851.5869-16-casey@schaufler-ca.com>
Date: Sat, 21 Jun 2025 10:18:50 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: casey@...aufler-ca.com,
	paul@...l-moore.com,
	eparis@...hat.com,
	linux-security-module@...r.kernel.org,
	audit@...r.kernel.org
Cc: jmorris@...ei.org,
	serge@...lyn.com,
	keescook@...omium.org,
	john.johansen@...onical.com,
	penguin-kernel@...ove.sakura.ne.jp,
	stephen.smalley.work@...il.com,
	linux-kernel@...r.kernel.org,
	selinux@...r.kernel.org
Subject: [RFC PATCH 15/15] LSM: Remove exclusive LSM flag

Only SELinux specifies LSM_FLAG_EXCLUSIVE, so there is no point in
enforcing it. There is no expectation that new exclusive security
modules will be accepted, as the reasons for exclusivity have been
addressed. The LSM_FLAG_EXCLUSIVE flag and its enforcement can be
removed.

Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
---
 include/linux/lsm_hooks.h |  1 -
 security/lsm_init.c       | 17 +----------------
 security/selinux/hooks.c  |  2 +-
 3 files changed, 2 insertions(+), 18 deletions(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 06e840fd4b63..717541fcd653 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -149,7 +149,6 @@ extern void security_add_hooks(struct security_hook_list *hooks, int count,
 			       const struct lsm_id *lsmid);
 
 #define LSM_FLAG_LEGACY_MAJOR	BIT(0)
-#define LSM_FLAG_EXCLUSIVE	BIT(1)
 
 enum lsm_order {
 	LSM_ORDER_FIRST = -1,	/* This is only for capabilities. */
diff --git a/security/lsm_init.c b/security/lsm_init.c
index 784f8296966f..3d8f59104d8f 100644
--- a/security/lsm_init.c
+++ b/security/lsm_init.c
@@ -28,7 +28,6 @@ static __initdata const char *lsm_order_cmdline;
 static __initdata const char *lsm_order_legacy;
 
 /* Ordered list of LSMs to initialize. */
-static __initdata struct lsm_info *lsm_exclusive;
 static __initdata struct lsm_info *lsm_order[MAX_LSM_COUNT + 1];
 
 #define lsm_order_for_each(iter)					\
@@ -150,8 +149,7 @@ static bool __init lsm_order_exists(struct lsm_info *lsm)
  * @src: source of the addition
  *
  * Append @lsm to the enabled LSM array after ensuring that it hasn't been
- * explicitly disabled, is a duplicate entry, or would run afoul of the
- * LSM_FLAG_EXCLUSIVE logic.
+ * explicitly disabled or is a duplicate entry.
  */
 static void __init lsm_order_append(struct lsm_info *lsm, const char *src)
 {
@@ -173,19 +171,6 @@ static void __init lsm_order_append(struct lsm_info *lsm, const char *src)
 		return;
 	}
 
-	if (lsm->flags & LSM_FLAG_EXCLUSIVE) {
-		if (lsm_exclusive) {
-			lsm_pr_dbg("skip exclusive LSM conflict %s:%s\n",
-				   src, lsm->id->name);
-			lsm_enabled_set(lsm, false);
-			return;
-		} else {
-			lsm_pr_dbg("select exclusive LSM %s:%s\n",
-				   src, lsm->id->name);
-			lsm_exclusive = lsm;
-		}
-	}
-
 	lsm_enabled_set(lsm, true);
 	lsm_order[lsm_count] = lsm;
 	lsm_idlist[lsm_count++] = lsm->id;
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 9578b63bbd2a..039d03be91f0 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -7675,7 +7675,7 @@ void selinux_complete_init(void)
    all processes and objects when they are created. */
 DEFINE_LSM(selinux) = {
 	.id = &selinux_lsmid,
-	.flags = LSM_FLAG_LEGACY_MAJOR | LSM_FLAG_EXCLUSIVE,
+	.flags = LSM_FLAG_LEGACY_MAJOR,
 	.enabled = &selinux_enabled_boot,
 	.blobs = &selinux_blob_sizes,
 	.init = selinux_init,
-- 
2.47.0