linux-kernel - [PATCH v1 4/8] LSM: Maintain a table of LSM attribute data

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Date:   Tue, 25 Oct 2022 11:45:15 -0700
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 v1 4/8] 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 | 17 +++++++++++++++++
 security/security.c      | 18 ++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/include/linux/security.h b/include/linux/security.h
index ca1b7109c0db..e1678594d983 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -138,6 +138,23 @@ enum lockdown_reason {
 
 extern const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1];
 
+#define LSMID_ENTRIES ( \
+	1 + /* capabilities */ \
+	(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 int lsm_id;
+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 b2eb0ccd954b..bf206996a2af 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
@@ -320,6 +321,12 @@ static void __init lsm_early_task(struct task_struct *task);
 
 static int lsm_append(const char *new, char **result);
 
+/*
+ * Current index to use while initializing the lsm id list.
+ */
+int lsm_id __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;
@@ -364,6 +371,7 @@ static void __init ordered_lsm_init(void)
 	for (lsm = ordered_lsms; *lsm; lsm++)
 		initialize_lsm(*lsm);
 
+	init_debug("lsm count            = %d\n", lsm_id);
 	kfree(ordered_lsms);
 }
 
@@ -485,6 +493,16 @@ 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_id == 0 || lsm_idlist[lsm_id - 1] != lsmid)
+		lsm_idlist[lsm_id++] = lsmid;
+
+	if (lsm_id > 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);
-- 
2.37.3