[PATCH security-next v4 19/32] LSM: Prepare for reorganizing "security=" logic

[Kees Cook]

This moves the string handling for "security=" boot parameter into
a stored pointer instead of a string duplicate. This will allow
easier handling of the string when switching logic to use the coming
enable/disable infrastructure.

Signed-off-by: Kees Cook <keesc...@chromium.org>
Reviewed-by: Casey Schaufler <ca...@schaufler-ca.com>
Reviewed-by: John Johansen <john.johan...@canonical.com>
---
 security/security.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/security/security.c b/security/security.c
index 3fff2d1d1ec4..455ba2767965 100644
--- a/security/security.c
+++ b/security/security.c
@@ -34,18 +34,14 @@
 
 #define MAX_LSM_EVM_XATTR      2
 
-/* Maximum number of letters for an LSM name string */
-#define SECURITY_NAME_MAX      10
-
 struct security_hook_heads security_hook_heads __lsm_ro_after_init;
 static ATOMIC_NOTIFIER_HEAD(lsm_notifier_chain);
 
 char *lsm_names;
 /* Boot-time LSM user choice */
-static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
-       CONFIG_DEFAULT_SECURITY;
 static __initdata const char *chosen_lsm_enable;
 static __initdata const char *chosen_lsm_disable;
+static __initdata const char *chosen_major_lsm;
 
 static __initconst const char * const builtin_lsm_enable = CONFIG_LSM_ENABLE;
 
@@ -112,7 +108,7 @@ static bool __init lsm_allowed(struct lsm_info *lsm)
                return true;
 
        /* Disabled if this LSM isn't the chosen one. */
-       if (strcmp(lsm->name, chosen_lsm) != 0)
+       if (strcmp(lsm->name, chosen_major_lsm) != 0)
                return false;
 
        return true;
@@ -191,6 +187,9 @@ static void __init prepare_lsm_enable(void)
        /* Process "lsm.enable=" and "lsm.disable=", if given. */
        parse_lsm_enable(chosen_lsm_enable, set_enabled, true);
        parse_lsm_enable(chosen_lsm_disable, set_enabled, false);
+
+       if (!chosen_major_lsm)
+               chosen_major_lsm = CONFIG_DEFAULT_SECURITY;
 }
 
 /**
@@ -231,12 +230,12 @@ int __init security_init(void)
 }
 
 /* Save user chosen LSM */
-static int __init choose_lsm(char *str)
+static int __init choose_major_lsm(char *str)
 {
-       strncpy(chosen_lsm, str, SECURITY_NAME_MAX);
+       chosen_major_lsm = str;
        return 1;
 }
-__setup("security=", choose_lsm);
+__setup("security=", choose_major_lsm);
 
 /* Enable LSM order debugging. */
 static int __init enable_debug(char *str)
-- 
2.17.1