linux-kernel - [PATCH v10 02/11] LSM: Maintain a table of LSM attribute data

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Date:   Fri, 28 Apr 2023 13:26:42 -0700
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     casey@...aufler-ca.com, paul@...l-moore.com,
        linux-security-module@...r.kernel.org
Cc:     jmorris@...ei.org, keescook@...omium.org,
        john.johansen@...onical.com, penguin-kernel@...ove.sakura.ne.jp,
        stephen.smalley.work@...il.com, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, mic@...ikod.net
Subject: [PATCH v10 02/11] LSM: Maintain a table of LSM attribute data

As LSMs are registered add their lsm_id pointers to a table.
This will be used later for attribute reporting.

Determine the number of possible security modules based on
their respective CONFIG options. This allows the number to be
known at build time. This allows data structures and tables
to use the constant.

Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
---
 include/linux/security.h |  2 ++
 security/security.c      | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/include/linux/security.h b/include/linux/security.h
index 5984d0d550b4..e70fc863b04a 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -138,6 +138,8 @@ enum lockdown_reason {
 };
 
 extern const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1];
+extern u32 lsm_active_cnt;
+extern struct lsm_id *lsm_idlist[];
 
 /* These functions are in security/commoncap.c */
 extern int cap_capable(const struct cred *cred, struct user_namespace *ns,
diff --git a/security/security.c b/security/security.c
index a482c6048df9..e390001a32c9 100644
--- a/security/security.c
+++ b/security/security.c
@@ -35,6 +35,25 @@
 /* How many LSMs were built into the kernel? */
 #define LSM_COUNT (__end_lsm_info - __start_lsm_info)
 
+/*
+ * How many LSMs are built into the kernel as determined at
+ * build time. Used to determine fixed array sizes.
+ * The capability module is accounted for by CONFIG_SECURITY
+ */
+#define LSM_CONFIG_COUNT ( \
+	(IS_ENABLED(CONFIG_SECURITY) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_SELINUX) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_SMACK) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_TOMOYO) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_IMA) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_APPARMOR) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_YAMA) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_LOADPIN) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_SAFESETID) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_LOCKDOWN_LSM) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_BPF_LSM) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_LANDLOCK) ? 1 : 0))
+
 /*
  * These are descriptions of the reasons that can be passed to the
  * security_locked_down() LSM hook. Placing this array here allows
@@ -244,6 +263,12 @@ static void __init initialize_lsm(struct lsm_info *lsm)
 	}
 }
 
+/*
+ * Current index to use while initializing the lsm id list.
+ */
+u32 lsm_active_cnt __lsm_ro_after_init;
+struct lsm_id *lsm_idlist[LSM_CONFIG_COUNT] __lsm_ro_after_init;
+
 /* Populate ordered LSMs list from comma-separated LSM name list. */
 static void __init ordered_lsm_parse(const char *order, const char *origin)
 {
@@ -513,6 +538,17 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
 {
 	int i;
 
+	if (lsm_active_cnt >= LSM_CONFIG_COUNT)
+		panic("%s Too many LSMs registered.\n", __func__);
+	/*
+	 * A security module may call security_add_hooks() more
+	 * than once during initialization, and LSM initialization
+	 * is serialized. Landlock is one such case.
+	 * Look at the previous entry, if there is one, for duplication.
+	 */
+	if (lsm_active_cnt == 0 || lsm_idlist[lsm_active_cnt - 1] != lsmid)
+		lsm_idlist[lsm_active_cnt++] = lsmid;
+
 	for (i = 0; i < count; i++) {
 		hooks[i].lsmid = lsmid;
 		hlist_add_tail_rcu(&hooks[i].list, hooks[i].head);
-- 
2.39.2