LSM: Prepare for reorganizing "security=" logic

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 <keescook@chromium.org>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>

1 files changed, 8 insertions, 9 deletions

diff --git a/security/security.c b/security/security.c
index b6d3456978a4..1e1f34285e96 100644
--- a/security/security.c
+++ b/security/security.c
@@ -34,9 +34,6 @@
 
 #define MAX_LSM_EVM_XATTR       2
 
-/* Maximum number of letters for an LSM name string */
-#define SECURITY_NAME_MAX       10
-
 /* How many LSMs were built into the kernel? */
 #define LSM_COUNT (__end_lsm_info - __start_lsm_info)
 
@@ -45,9 +42,8 @@ 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_order;
+static __initdata const char *chosen_major_lsm;
 
 static __initconst const char * const builtin_lsm_order = CONFIG_LSM;
 
@@ -138,7 +134,7 @@ 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;
@@ -168,6 +164,9 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
         struct lsm_info *lsm;
         char *sep, *name, *next;
 
+        if (!chosen_major_lsm)
+                chosen_major_lsm = CONFIG_DEFAULT_SECURITY;
+
         sep = kstrdup(order, GFP_KERNEL);
         next = sep;
         /* Walk the list, looking for matching LSMs. */
@@ -257,12 +256,12 @@ 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);
 
 /* Explicitly choose LSM initialization order. */
 static int __init choose_lsm_order(char *str)