linux-kernel - [PATCH v5 18/38] LSM: Introduce enum lsm

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Date:   Tue, 11 Dec 2018 14:42:54 -0800
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     jmorris@...ei.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, selinux@...r.kernel.org
Cc:     john.johansen@...onical.com, keescook@...omium.org,
        penguin-kernel@...ove.sakura.ne.jp, paul@...l-moore.com,
        linux-fsdevel@...r.kernel.org, sds@...ho.nsa.gov,
        adobriyan@...il.com, mic@...ikod.net, s.mesoraca16@...il.com,
        casey@...aufler-ca.com
Subject: [PATCH v5 18/38] LSM: Introduce enum lsm_order

From: Kees Cook <keescook@...omium.org>

In preparation for distinguishing the "capability" LSM from other LSMs, it
must be ordered first. This introduces LSM_ORDER_MUTABLE for the general
LSMs and LSM_ORDER_FIRST for capability. In the future LSM_ORDER_LAST
for could be added for anything that must run last (e.g. Landlock may
use this).

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/linux/lsm_hooks.h | 6 ++++++
 security/security.c       | 9 ++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 6cfbd7d78a89..83858e3df9e5 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -2042,8 +2042,14 @@ extern void security_add_hooks(struct security_hook_list *hooks, int count,
 #define LSM_FLAG_LEGACY_MAJOR	BIT(0)
 #define LSM_FLAG_EXCLUSIVE	BIT(1)
 
+enum lsm_order {
+	LSM_ORDER_FIRST = -1,	/* This is only for capabilities. */
+	LSM_ORDER_MUTABLE = 0,
+};
+
 struct lsm_info {
 	const char *name;	/* Required. */
+	enum lsm_order order;	/* Optional: default is LSM_ORDER_MUTABLE */
 	unsigned long flags;	/* Optional: flags describing LSM */
 	int *enabled;		/* Optional: controlled by CONFIG_LSM */
 	int (*init)(void);	/* Required. */
diff --git a/security/security.c b/security/security.c
index 0c3c66dbf51c..701507174f40 100644
--- a/security/security.c
+++ b/security/security.c
@@ -174,6 +174,12 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
 	struct lsm_info *lsm;
 	char *sep, *name, *next;
 
+	/* LSM_ORDER_FIRST is always first. */
+	for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
+		if (lsm->order == LSM_ORDER_FIRST)
+			append_ordered_lsm(lsm, "first");
+	}
+
 	/* Process "security=", if given. */
 	if (chosen_major_lsm) {
 		struct lsm_info *major;
@@ -202,7 +208,8 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
 		bool found = false;
 
 		for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
-			if (strcmp(lsm->name, name) == 0) {
+			if (lsm->order == LSM_ORDER_MUTABLE &&
+			    strcmp(lsm->name, name) == 0) {
 				append_ordered_lsm(lsm, origin);
 				found = true;
 			}
-- 
2.14.5