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Subject[PATCH security-next v5 16/30] LSM: Build ordered list of LSMs to initialize
Date
This constructs an ordered list of LSMs to initialize, using a hard-coded
list of only "integrity": minor LSMs continue to have direct hook calls,
and major LSMs continue to initialize separately.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
---
security/security.c | 58 +++++++++++++++++++++++++++++++++++++++++----
1 file changed, 53 insertions(+), 5 deletions(-)

diff --git a/security/security.c b/security/security.c
index 8968c98e0a0e..9bb15d697287 100644
--- a/security/security.c
+++ b/security/security.c
@@ -37,6 +37,9 @@
/* 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)
+
struct security_hook_heads security_hook_heads __lsm_ro_after_init;
static ATOMIC_NOTIFIER_HEAD(lsm_notifier_chain);

@@ -45,6 +48,9 @@ char *lsm_names;
static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
CONFIG_DEFAULT_SECURITY;

+/* Ordered list of LSMs to initialize. */
+static __initdata struct lsm_info **ordered_lsms;
+
static __initdata bool debug;
#define init_debug(...) \
do { \
@@ -85,6 +91,34 @@ static void __init set_enabled(struct lsm_info *lsm, bool enabled)
}
}

+/* Is an LSM already listed in the ordered LSMs list? */
+static bool __init exists_ordered_lsm(struct lsm_info *lsm)
+{
+ struct lsm_info **check;
+
+ for (check = ordered_lsms; *check; check++)
+ if (*check == lsm)
+ return true;
+
+ return false;
+}
+
+/* Append an LSM to the list of ordered LSMs to initialize. */
+static int last_lsm __initdata;
+static void __init append_ordered_lsm(struct lsm_info *lsm, const char *from)
+{
+ /* Ignore duplicate selections. */
+ if (exists_ordered_lsm(lsm))
+ return;
+
+ if (WARN(last_lsm == LSM_COUNT, "%s: out of LSM slots!?\n", from))
+ return;
+
+ ordered_lsms[last_lsm++] = lsm;
+ init_debug("%s ordering: %s (%sabled)\n", from, lsm->name,
+ is_enabled(lsm) ? "en" : "dis");
+}
+
/* Is an LSM allowed to be initialized? */
static bool __init lsm_allowed(struct lsm_info *lsm)
{
@@ -121,18 +155,32 @@ static void __init maybe_initialize_lsm(struct lsm_info *lsm)
}
}

-static void __init ordered_lsm_init(void)
+/* Populate ordered LSMs list from single LSM name. */
+static void __init ordered_lsm_parse(const char *order, const char *origin)
{
struct lsm_info *lsm;

for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
- if ((lsm->flags & LSM_FLAG_LEGACY_MAJOR) != 0)
- continue;
-
- maybe_initialize_lsm(lsm);
+ if (strcmp(lsm->name, order) == 0)
+ append_ordered_lsm(lsm, origin);
}
}

+static void __init ordered_lsm_init(void)
+{
+ struct lsm_info **lsm;
+
+ ordered_lsms = kcalloc(LSM_COUNT + 1, sizeof(*ordered_lsms),
+ GFP_KERNEL);
+
+ ordered_lsm_parse("integrity", "builtin");
+
+ for (lsm = ordered_lsms; *lsm; lsm++)
+ maybe_initialize_lsm(*lsm);
+
+ kfree(ordered_lsms);
+}
+
static void __init major_lsm_init(void)
{
struct lsm_info *lsm;
--
2.17.1
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