linux-kernel - [PATCH v4 2/8] LSM: Maintain a table of LSM attribute data

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Message-Id: <20221229233454.43880-3-casey@schaufler-ca.com>
Date:   Thu, 29 Dec 2022 15:34:48 -0800
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     casey.schaufler@...el.com, paul@...l-moore.com,
        linux-security-module@...r.kernel.org
Cc:     casey@...aufler-ca.com, 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 v4 2/8] 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.

Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
---
 include/linux/security.h | 18 ++++++++++++++++++
 security/security.c      | 18 ++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/include/linux/security.h b/include/linux/security.h
index 5b67f208f7de..e70d546acf3d 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -139,6 +139,24 @@ enum lockdown_reason {
 
 extern const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1];
 
+/* The capability module is accounted for by CONFIG_SECURITY */
+#define LSMID_ENTRIES ( \
+	(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_SECURITY_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) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_BPF_LSM) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_SECURITY_LANDLOCK) ? 1 : 0))
+
+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,
 		       int cap, unsigned int opts);
diff --git a/security/security.c b/security/security.c
index 07a8fe7f92bf..4acb14500bc3 100644
--- a/security/security.c
+++ b/security/security.c
@@ -28,6 +28,7 @@
 #include <linux/backing-dev.h>
 #include <linux/string.h>
 #include <linux/msg.h>
+#include <uapi/linux/lsm.h>
 #include <net/flow.h>
 
 #define MAX_LSM_EVM_XATTR	2
@@ -341,6 +342,12 @@ static void __init report_lsm_order(void)
 	pr_cont("\n");
 }
 
+/*
+ * Current index to use while initializing the lsm id list.
+ */
+u32 lsm_active_cnt __lsm_ro_after_init;
+struct lsm_id *lsm_idlist[LSMID_ENTRIES] __lsm_ro_after_init;
+
 static void __init ordered_lsm_init(void)
 {
 	struct lsm_info **lsm;
@@ -388,6 +395,7 @@ static void __init ordered_lsm_init(void)
 	for (lsm = ordered_lsms; *lsm; lsm++)
 		initialize_lsm(*lsm);
 
+	init_debug("lsm count            = %d\n", lsm_active_cnt);
 	kfree(ordered_lsms);
 }
 
@@ -513,6 +521,16 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
 {
 	int i;
 
+	/*
+	 * A security module may call security_add_hooks() more
+	 * than once. Landlock is one such case.
+	 */
+	if (lsm_active_cnt == 0 || lsm_idlist[lsm_active_cnt -1] != lsmid)
+		lsm_idlist[lsm_active_cnt++] = lsmid;
+
+	if (lsm_active_cnt > LSMID_ENTRIES)
+		panic("%s Too many LSMs registered.\n", __func__);
+
 	for (i = 0; i < count; i++) {
 		hooks[i].lsmid = lsmid;
 		hlist_add_tail_rcu(&hooks[i].list, hooks[i].head);
-- 
2.38.1