[PATCH security-next v3 23/29] LSM: Introduce "lsm.order=" for boottime ordering

[Kees Cook]

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 <keesc...@chromium.org>
---
 Documentation/admin-guide/kernel-parameters.txt |  6 ++++++
 security/security.c                             | 14 +++++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt 
b/Documentation/admin-guide/kernel-parameters.txt
index 67c90985d2b8..c7c1a0d253ee 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2288,6 +2288,12 @@
                        CONFIG_LSM_ENABLE, and any per-LSM CONFIGs and
                        boot parameters.
 
+       lsm.order=lsm1,...,lsmN
+                       [SECURITY] Choose order of enabled LSM
+                       initialization. Any builtin LSMs not listed here
+                       will be implicitly appended 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 e38df0314f5e..f1c3581d870f 100644
--- a/security/security.c
+++ b/security/security.c
@@ -44,6 +44,7 @@ char *lsm_names;
 /* Boot-time LSM user choice */
 static __initdata const char *chosen_lsm_enable;
 static __initdata const char *chosen_lsm_disable;
+static __initdata const char *chosen_lsm_order;
 static __initdata const char *chosen_major_lsm;
 
 static __initconst const char * const builtin_lsm_enable = CONFIG_LSM_ENABLE;
@@ -160,11 +161,14 @@ 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. */
+       parse_lsm_order(chosen_lsm_order, "cmdline");
+
        /* Parse order from builtin list. */
        parse_lsm_order(builtin_lsm_order, "builtin");
 
@@ -324,6 +328,14 @@ 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