[PATCH security-next v2 20/26] LSM: Introduce "lsm.order=" for boottime ordering

[Kees Cook <keescook@xxxxxxxxxxxx>]

Provide a way to reorder LSM initialization using the new "lsm.order="
comma-separated list of LSMs. Any LSMs not listed will be added in builtin
order.

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 Documentation/admin-guide/kernel-parameters.txt |  5 +++++
 security/security.c                             | 15 ++++++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 32d323ee9218..5ac4c1056ffa 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2276,6 +2276,11 @@
 
 	lsm.debug	[SECURITY] Enable LSM initialization debugging output.
 
+	lsm.order=lsm1,...,lsmN
+			[SECURITY] Choose order of LSM initialization. Any
+			builtin LSMs not listed here will be implicitly
+			added to the list in builtin order.
+
 	machvec=	[IA-64] Force the use of a particular machine-vector
 			(machvec) in a generic kernel.
 			Example: machvec=hpzx1_swiotlb
diff --git a/security/security.c b/security/security.c
index 063ee2466e58..4db194f81419 100644
--- a/security/security.c
+++ b/security/security.c
@@ -43,6 +43,7 @@ static ATOMIC_NOTIFIER_HEAD(lsm_notifier_chain);
 char *lsm_names;
 /* Boot-time LSM user choice */
 static __initdata const char *chosen_major_lsm;
+static __initdata const char *chosen_lsm_order;
 
 static __initconst const char * const builtin_lsm_order = CONFIG_LSM_ORDER;
 
@@ -136,11 +137,15 @@ static void __init parse_lsm_order(const char *order, const char *origin)
 	kfree(sep);
 }
 
-/* Populate ordered LSMs list from builtin list of LSMs. */
+/* Populate ordered LSMs list from commandline and builtin list of LSMs. */
 static void __init prepare_lsm_order(void)
 {
 	struct lsm_info *lsm;
 
+	/* Parse order from commandline, if present. */
+	if (chosen_lsm_order)
+		parse_lsm_order(chosen_lsm_order, "cmdline");
+
 	/* Parse order from builtin list. */
 	parse_lsm_order(builtin_lsm_order, "builtin");
 
@@ -264,6 +269,14 @@ static int __init choose_major_lsm(char *str)
 }
 __setup("security=", choose_major_lsm);
 
+/* Explicitly choose LSM initialization order. */
+static int __init choose_lsm_order(char *str)
+{
+	chosen_lsm_order = str;
+	return 1;
+}
+__setup("lsm.order=", choose_lsm_order);
+
 /* Enable LSM order debugging. */
 static int __init enable_debug(char *str)
 {
-- 
2.17.1