LSM: Ignore "security=" when "lsm=" is specified

To avoid potential confusion, explicitly ignore "security=" when "lsm=" is
used on the command line, and report that it is happening.
Suggested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <james.morris@microsoft.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -2321,7 +2321,7 @@
 
 	lsm=lsm1,...,lsmN
 			[SECURITY] Choose order of LSM initialization. This
-			overrides CONFIG_LSM.
+			overrides CONFIG_LSM, and the "security=" parameter.
 
 	machvec=	[IA-64] Force the use of a particular machine-vector
 			(machvec) in a generic kernel.
@@ -4094,11 +4094,9 @@
 			Note: increases power consumption, thus should only be
 			enabled if running jitter sensitive (HPC/RT) workloads.
 
-	security=	[SECURITY] Choose a security module to enable at boot.
-			If this boot parameter is not specified, only the first
-			security module asking for security registration will be
-			loaded. An invalid security module name will be treated
-			as if no module has been chosen.
+	security=	[SECURITY] Choose a legacy "major" security module to
+			enable at boot. This has been deprecated by the
+			"lsm=" parameter.
 
 	selinux=	[SELINUX] Disable or enable SELinux at boot time.
 			Format: { "0" | "1" }

security/security.c

@@ -288,9 +288,13 @@ static void __init ordered_lsm_init(void)
 	ordered_lsms = kcalloc(LSM_COUNT + 1, sizeof(*ordered_lsms),
 				GFP_KERNEL);
 
-	if (chosen_lsm_order)
+	if (chosen_lsm_order) {
+		if (chosen_major_lsm) {
+			pr_info("security= is ignored because it is superseded by lsm=\n");
+			chosen_major_lsm = NULL;
+		}
 		ordered_lsm_parse(chosen_lsm_order, "cmdline");
-	else
+	} else
 		ordered_lsm_parse(builtin_lsm_order, "builtin");
 
 	for (lsm = ordered_lsms; *lsm; lsm++)