TOMOYO: Abstract use of cred security blob

Don't use the cred->security pointer directly.
Provide helper functions that provide the security blob pointer.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
[kees: adjusted for ordered init series]
Signed-off-by: Kees Cook <keescook@chromium.org>

1 files changed, 31 insertions, 9 deletions

diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
index daff7d7897ad..15864307925d 100644
--- a/security/tomoyo/tomoyo.c
+++ b/security/tomoyo/tomoyo.c
@@ -18,7 +18,9 @@
  */
 static int tomoyo_cred_alloc_blank(struct cred *new, gfp_t gfp)
 {
-	new->security = NULL;
+	struct tomoyo_domain_info **blob = tomoyo_cred(new);
+
+	*blob = NULL;
 	return 0;
 }
 
@@ -34,8 +36,13 @@ static int tomoyo_cred_alloc_blank(struct cred *new, gfp_t gfp)
 static int tomoyo_cred_prepare(struct cred *new, const struct cred *old,
 			       gfp_t gfp)
 {
-	struct tomoyo_domain_info *domain = old->security;
-	new->security = domain;
+	struct tomoyo_domain_info **old_blob = tomoyo_cred(old);
+	struct tomoyo_domain_info **new_blob = tomoyo_cred(new);
+	struct tomoyo_domain_info *domain;
+
+	domain = *old_blob;
+	*new_blob = domain;
+
 	if (domain)
 		atomic_inc(&domain->users);
 	return 0;
@@ -59,7 +66,9 @@ static void tomoyo_cred_transfer(struct cred *new, const struct cred *old)
  */
 static void tomoyo_cred_free(struct cred *cred)
 {
-	struct tomoyo_domain_info *domain = cred->security;
+	struct tomoyo_domain_info **blob = tomoyo_cred(cred);
+	struct tomoyo_domain_info *domain = *blob;
+
 	if (domain)
 		atomic_dec(&domain->users);
 }
@@ -73,6 +82,9 @@ static void tomoyo_cred_free(struct cred *cred)
  */
 static int tomoyo_bprm_set_creds(struct linux_binprm *bprm)
 {
+	struct tomoyo_domain_info **blob;
+	struct tomoyo_domain_info *domain;
+
 	/*
 	 * Do only if this function is called for the first time of an execve
 	 * operation.
@@ -93,13 +105,14 @@ static int tomoyo_bprm_set_creds(struct linux_binprm *bprm)
 	 * stored inside "bprm->cred->security" will be acquired later inside
 	 * tomoyo_find_next_domain().
 	 */
-	atomic_dec(&((struct tomoyo_domain_info *)
-		     bprm->cred->security)->users);
+	blob = tomoyo_cred(bprm->cred);
+	domain = *blob;
+	atomic_dec(&domain->users);
 	/*
 	 * Tell tomoyo_bprm_check_security() is called for the first time of an
 	 * execve operation.
 	 */
-	bprm->cred->security = NULL;
+	*blob = NULL;
 	return 0;
 }
 
@@ -112,8 +125,11 @@ static int tomoyo_bprm_set_creds(struct linux_binprm *bprm)
  */
 static int tomoyo_bprm_check_security(struct linux_binprm *bprm)
 {
-	struct tomoyo_domain_info *domain = bprm->cred->security;
+	struct tomoyo_domain_info **blob;
+	struct tomoyo_domain_info *domain;
 
+	blob = tomoyo_cred(bprm->cred);
+	domain = *blob;
 	/*
 	 * Execute permission is checked against pathname passed to do_execve()
 	 * using current domain.
@@ -531,6 +547,8 @@ static struct security_hook_list tomoyo_hooks[] __lsm_ro_after_init = {
 /* Lock for GC. */
 DEFINE_SRCU(tomoyo_ss);
 
+int tomoyo_enabled __lsm_ro_after_init = 1;
+
 /**
  * tomoyo_init - Register TOMOYO Linux as a LSM module.
  *
@@ -539,17 +557,21 @@ DEFINE_SRCU(tomoyo_ss);
 static int __init tomoyo_init(void)
 {
 	struct cred *cred = (struct cred *) current_cred();
+	struct tomoyo_domain_info **blob;
 
 	/* register ourselves with the security framework */
 	security_add_hooks(tomoyo_hooks, ARRAY_SIZE(tomoyo_hooks), "tomoyo");
 	printk(KERN_INFO "TOMOYO Linux initialized\n");
-	cred->security = &tomoyo_kernel_domain;
+	blob = tomoyo_cred(cred);
+	*blob = &tomoyo_kernel_domain;
 	tomoyo_mm_init();
+
 	return 0;
 }
 
 DEFINE_LSM(tomoyo) = {
 	.name = "tomoyo",
+	.enabled = &tomoyo_enabled,
 	.flags = LSM_FLAG_LEGACY_MAJOR | LSM_FLAG_EXCLUSIVE,
 	.init = tomoyo_init,
 };