linux-kernel - [PATCH security-next v5 26/30] LSM: Split LSM preparation from initialization

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Date:   Wed, 10 Oct 2018 17:18:42 -0700
From:   Kees Cook <keescook@...omium.org>
To:     James Morris <jmorris@...ei.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Casey Schaufler <casey@...aufler-ca.com>,
        John Johansen <john.johansen@...onical.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Paul Moore <paul@...l-moore.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Jordan Glover <Golden_Miller83@...tonmail.ch>,
        LSM <linux-security-module@...r.kernel.org>,
        linux-doc@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH security-next v5 26/30] LSM: Split LSM preparation from initialization

Since we already have to do a pass through the LSMs to figure out if
exclusive LSMs should be disabled after the first one is seen as enabled,
this splits the logic up a bit more cleanly. Now we do a full "prepare"
pass through the LSMs (which also allows for later use by the blob-sharing
code), before starting the LSM initialization pass.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 security/security.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/security/security.c b/security/security.c
index 4f52bd06705f..b40c4c212892 100644
--- a/security/security.c
+++ b/security/security.c
@@ -139,22 +139,28 @@ static bool __init lsm_allowed(struct lsm_info *lsm)
 	return true;
 }
 
-/* Check if LSM should be initialized. */
-static void __init maybe_initialize_lsm(struct lsm_info *lsm)
+/* Prepare LSM for initialization. */
+static void __init prepare_lsm(struct lsm_info *lsm)
 {
 	int enabled = lsm_allowed(lsm);
 
 	/* Record enablement (to handle any following exclusive LSMs). */
 	set_enabled(lsm, enabled);
 
-	/* If selected, initialize the LSM. */
+	/* If enabled, do pre-initialization work. */
 	if (enabled) {
-		int ret;
-
 		if ((lsm->flags & LSM_FLAG_EXCLUSIVE) && !exclusive) {
 			exclusive = lsm;
 			init_debug("exclusive chosen: %s\n", lsm->name);
 		}
+	}
+}
+
+/* Initialize a given LSM, if it is enabled. */
+static void __init initialize_lsm(struct lsm_info *lsm)
+{
+	if (is_enabled(lsm)) {
+		int ret;
 
 		init_debug("initializing %s\n", lsm->name);
 		ret = lsm->init();
@@ -230,7 +236,10 @@ static void __init ordered_lsm_init(void)
 		ordered_lsm_parse(builtin_lsm_order, "builtin");
 
 	for (lsm = ordered_lsms; *lsm; lsm++)
-		maybe_initialize_lsm(*lsm);
+		prepare_lsm(*lsm);
+
+	for (lsm = ordered_lsms; *lsm; lsm++)
+		initialize_lsm(*lsm);
 
 	kfree(ordered_lsms);
 }
-- 
2.17.1