tomoyo: Swicth from cred->security to task_struct->security.

TOMOYO security module is designed to use "struct task_struct"->security
in order to allow per "struct task_struct" tracking without being disturbed
by unable to update "struct cred"->security due to override mechanism.

Now that infrastructure-managed security blob is ready, this patch updates
TOMOYO to use "struct task_struct"->security.

Signed-off-by: Tetsuo Handa <[e-mail]>
Signed-off-by: James Morris <[e-mail]>

security/tomoyo/common.c

···
 		else
 			p = find_task_by_vpid(pid);
 		if (p)
-			domain = tomoyo_real_domain(p);
+			domain = tomoyo_task(p)->domain_info;
 		rcu_read_unlock();
 	} else if (!strncmp(data, "domain=", 7)) {
 		if (tomoyo_domain_def(data + 7))
···
 	else
 		p = find_task_by_vpid(pid);
 	if (p)
-		domain = tomoyo_real_domain(p);
+		domain = tomoyo_task(p)->domain_info;
 	rcu_read_unlock();
 	if (!domain)
 		return;

security/tomoyo/common.h

···
 	u8 group;          /* Group number to use.   */
 	bool is_deleted;   /* Delete flag.           */
 	bool flags[TOMOYO_MAX_DOMAIN_INFO_FLAGS];
-	atomic_t users; /* Number of referring credentials. */
+	atomic_t users; /* Number of referring tasks. */
 };
 
 /*
···
 	const char *name;
 };
 
+/* Structure for "struct task_struct"->security. */
+struct tomoyo_task {
+	struct tomoyo_domain_info *domain_info;
+	struct tomoyo_domain_info *old_domain_info;
+};
+
 /********** Function prototypes. **********/
 
 bool tomoyo_address_matches_group(const bool is_ipv6, const __be32 *address,
···
 struct tomoyo_condition *tomoyo_get_condition(struct tomoyo_acl_param *param);
 struct tomoyo_domain_info *tomoyo_assign_domain(const char *domainname,
 						const bool transit);
+struct tomoyo_domain_info *tomoyo_domain(void);
 struct tomoyo_domain_info *tomoyo_find_domain(const char *domainname);
 struct tomoyo_group *tomoyo_get_group(struct tomoyo_acl_param *param,
 				      const u8 idx);
···
 }
 
 /**
- * tomoyo_cred - Get a pointer to the tomoyo cred security blob
- * @cred - the relevant cred
+ * tomoyo_task - Get "struct tomoyo_task" for specified thread.
  *
- * Returns pointer to the tomoyo cred blob.
+ * @task - Pointer to "struct task_struct".
+ *
+ * Returns pointer to "struct tomoyo_task" for specified thread.
  */
-static inline struct tomoyo_domain_info **tomoyo_cred(const struct cred *cred)
+static inline struct tomoyo_task *tomoyo_task(struct task_struct *task)
 {
-	return cred->security + tomoyo_blob_sizes.lbs_cred;
-}
-
-/**
- * tomoyo_domain - Get "struct tomoyo_domain_info" for current thread.
- *
- * Returns pointer to "struct tomoyo_domain_info" for current thread.
- */
-static inline struct tomoyo_domain_info *tomoyo_domain(void)
-{
-	struct tomoyo_domain_info **blob = tomoyo_cred(current_cred());
-
-	return *blob;
-}
-
-/**
- * tomoyo_real_domain - Get "struct tomoyo_domain_info" for specified thread.
- *
- * @task: Pointer to "struct task_struct".
- *
- * Returns pointer to "struct tomoyo_security" for specified thread.
- */
-static inline struct tomoyo_domain_info *tomoyo_real_domain(struct task_struct
-							    *task)
-{
-	struct tomoyo_domain_info **blob = tomoyo_cred(get_task_cred(task));
-
-	return *blob;
+	return task->security + tomoyo_blob_sizes.lbs_task;
 }
 
 /**

security/tomoyo/domain.c

···
  */
 int tomoyo_find_next_domain(struct linux_binprm *bprm)
 {
-	struct tomoyo_domain_info **blob;
 	struct tomoyo_domain_info *old_domain = tomoyo_domain();
 	struct tomoyo_domain_info *domain = NULL;
 	const char *original_name = bprm->filename;
···
 	if (!domain)
 		domain = old_domain;
 	/* Update reference count on "struct tomoyo_domain_info". */
-	atomic_inc(&domain->users);
-	blob = tomoyo_cred(bprm->cred);
-	*blob = domain;
+	{
+		struct tomoyo_task *s = tomoyo_task(current);
+
+		s->old_domain_info = s->domain_info;
+		s->domain_info = domain;
+		atomic_inc(&domain->users);
+	}
 	kfree(exename.name);
 	if (!retval) {
 		ee->r.domain = domain;

security/tomoyo/securityfs_if.c

···
 			if (!new_domain) {
 				error = -ENOENT;
 			} else {
-				struct cred *cred = prepare_creds();
-				if (!cred) {
-					error = -ENOMEM;
-				} else {
-					struct tomoyo_domain_info **blob;
-					struct tomoyo_domain_info *old_domain;
+				struct tomoyo_task *s = tomoyo_task(current);
+				struct tomoyo_domain_info *old_domain =
+					s->domain_info;
 
-					blob = tomoyo_cred(cred);
-					old_domain = *blob;
-					*blob = new_domain;
-					atomic_inc(&new_domain->users);
-					atomic_dec(&old_domain->users);
-					commit_creds(cred);
-					error = 0;
-				}
+				s->domain_info = new_domain;
+				atomic_inc(&new_domain->users);
+				atomic_dec(&old_domain->users);
+				error = 0;
 			}
 		}
 		tomoyo_read_unlock(idx);

security/tomoyo/tomoyo.c

···
 #include "common.h"
 
 /**
- * tomoyo_cred_alloc_blank - Target for security_cred_alloc_blank().
+ * tomoyo_domain - Get "struct tomoyo_domain_info" for current thread.
  *
- * @new: Pointer to "struct cred".
- * @gfp: Memory allocation flags.
- *
- * Returns 0.
+ * Returns pointer to "struct tomoyo_domain_info" for current thread.
  */
-static int tomoyo_cred_alloc_blank(struct cred *new, gfp_t gfp)
+struct tomoyo_domain_info *tomoyo_domain(void)
 {
-	struct tomoyo_domain_info **blob = tomoyo_cred(new);
+	struct tomoyo_task *s = tomoyo_task(current);
 
-	*blob = NULL;
-	return 0;
+	if (s->old_domain_info && !current->in_execve) {
+		atomic_dec(&s->old_domain_info->users);
+		s->old_domain_info = NULL;
+	}
+	return s->domain_info;
 }
 
 /**
···
 static int tomoyo_cred_prepare(struct cred *new, const struct cred *old,
 			       gfp_t gfp)
 {
-	struct tomoyo_domain_info **old_blob = tomoyo_cred(old);
-	struct tomoyo_domain_info **new_blob = tomoyo_cred(new);
-	struct tomoyo_domain_info *domain;
+	/* Restore old_domain_info saved by previous execve() request. */
+	struct tomoyo_task *s = tomoyo_task(current);
 
-	domain = *old_blob;
-	*new_blob = domain;
-
-	if (domain)
-		atomic_inc(&domain->users);
+	if (s->old_domain_info && !current->in_execve) {
+		atomic_dec(&s->domain_info->users);
+		s->domain_info = s->old_domain_info;
+		s->old_domain_info = NULL;
+	}
 	return 0;
 }
 
 /**
- * tomoyo_cred_transfer - Target for security_transfer_creds().
+ * tomoyo_bprm_committed_creds - Target for security_bprm_committed_creds().
  *
- * @new: Pointer to "struct cred".
- * @old: Pointer to "struct cred".
+ * @bprm: Pointer to "struct linux_binprm".
  */
-static void tomoyo_cred_transfer(struct cred *new, const struct cred *old)
+static void tomoyo_bprm_committed_creds(struct linux_binprm *bprm)
 {
-	tomoyo_cred_prepare(new, old, 0);
+	/* Clear old_domain_info saved by execve() request. */
+	struct tomoyo_task *s = tomoyo_task(current);
+
+	atomic_dec(&s->old_domain_info->users);
+	s->old_domain_info = NULL;
 }
 
-/**
- * tomoyo_cred_free - Target for security_cred_free().
- *
- * @cred: Pointer to "struct cred".
- */
-static void tomoyo_cred_free(struct cred *cred)
-{
-	struct tomoyo_domain_info **blob = tomoyo_cred(cred);
-	struct tomoyo_domain_info *domain = *blob;
-
-	if (domain)
-		atomic_dec(&domain->users);
-}
-
+#ifndef CONFIG_SECURITY_TOMOYO_OMIT_USERSPACE_LOADER
 /**
  * tomoyo_bprm_set_creds - Target for security_bprm_set_creds().
  *
  * @bprm: Pointer to "struct linux_binprm".
  *
- * Returns 0 on success, negative value otherwise.
+ * Returns 0.
  */
 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.
 	 */
 	if (bprm->called_set_creds)
 		return 0;
-#ifndef CONFIG_SECURITY_TOMOYO_OMIT_USERSPACE_LOADER
 	/*
 	 * Load policy if /sbin/tomoyo-init exists and /sbin/init is requested
 	 * for the first time.
 	 */
 	if (!tomoyo_policy_loaded)
 		tomoyo_load_policy(bprm->filename);
-#endif
-	/*
-	 * Release reference to "struct tomoyo_domain_info" stored inside
-	 * "bprm->cred->security". New reference to "struct tomoyo_domain_info"
-	 * stored inside "bprm->cred->security" will be acquired later inside
-	 * tomoyo_find_next_domain().
-	 */
-	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.
-	 */
-	*blob = NULL;
 	return 0;
 }
+#endif
 
 /**
  * tomoyo_bprm_check_security - Target for security_bprm_check().
···
  */
 static int tomoyo_bprm_check_security(struct linux_binprm *bprm)
 {
-	struct tomoyo_domain_info **blob;
-	struct tomoyo_domain_info *domain;
+	struct tomoyo_task *s = tomoyo_task(current);
 
-	blob = tomoyo_cred(bprm->cred);
-	domain = *blob;
 	/*
 	 * Execute permission is checked against pathname passed to do_execve()
 	 * using current domain.
 	 */
-	if (!domain) {
+	if (!s->old_domain_info) {
 		const int idx = tomoyo_read_lock();
 		const int err = tomoyo_find_next_domain(bprm);
 		tomoyo_read_unlock(idx);
···
 	/*
 	 * Read permission is checked against interpreters using next domain.
 	 */
-	return tomoyo_check_open_permission(domain, &bprm->file->f_path,
-					    O_RDONLY);
+	return tomoyo_check_open_permission(s->domain_info,
+					    &bprm->file->f_path, O_RDONLY);
 }
 
 /**
···
 }
 
 struct lsm_blob_sizes tomoyo_blob_sizes __lsm_ro_after_init = {
-	.lbs_cred = sizeof(struct tomoyo_domain_info *),
+	.lbs_task = sizeof(struct tomoyo_task),
 };
+
+/**
+ * tomoyo_task_alloc - Target for security_task_alloc().
+ *
+ * @task:  Pointer to "struct task_struct".
+ * @flags: clone() flags.
+ *
+ * Returns 0.
+ */
+static int tomoyo_task_alloc(struct task_struct *task,
+			     unsigned long clone_flags)
+{
+	struct tomoyo_task *old = tomoyo_task(current);
+	struct tomoyo_task *new = tomoyo_task(task);
+
+	new->domain_info = old->domain_info;
+	atomic_inc(&new->domain_info->users);
+	new->old_domain_info = NULL;
+	return 0;
+}
+
+/**
+ * tomoyo_task_free - Target for security_task_free().
+ *
+ * @task: Pointer to "struct task_struct".
+ */
+static void tomoyo_task_free(struct task_struct *task)
+{
+	struct tomoyo_task *s = tomoyo_task(task);
+
+	if (s->domain_info) {
+		atomic_dec(&s->domain_info->users);
+		s->domain_info = NULL;
+	}
+	if (s->old_domain_info) {
+		atomic_dec(&s->old_domain_info->users);
+		s->old_domain_info = NULL;
+	}
+}
 
 /*
  * tomoyo_security_ops is a "struct security_operations" which is used for
  * registering TOMOYO.
  */
 static struct security_hook_list tomoyo_hooks[] __lsm_ro_after_init = {
-	LSM_HOOK_INIT(cred_alloc_blank, tomoyo_cred_alloc_blank),
 	LSM_HOOK_INIT(cred_prepare, tomoyo_cred_prepare),
-	LSM_HOOK_INIT(cred_transfer, tomoyo_cred_transfer),
-	LSM_HOOK_INIT(cred_free, tomoyo_cred_free),
+	LSM_HOOK_INIT(bprm_committed_creds, tomoyo_bprm_committed_creds),
+	LSM_HOOK_INIT(task_alloc, tomoyo_task_alloc),
+	LSM_HOOK_INIT(task_free, tomoyo_task_free),
+#ifndef CONFIG_SECURITY_TOMOYO_OMIT_USERSPACE_LOADER
 	LSM_HOOK_INIT(bprm_set_creds, tomoyo_bprm_set_creds),
+#endif
 	LSM_HOOK_INIT(bprm_check_security, tomoyo_bprm_check_security),
 	LSM_HOOK_INIT(file_fcntl, tomoyo_file_fcntl),
 	LSM_HOOK_INIT(file_open, tomoyo_file_open),
···
  */
 static int __init tomoyo_init(void)
 {
-	struct cred *cred = (struct cred *) current_cred();
-	struct tomoyo_domain_info **blob;
+	struct tomoyo_task *s = tomoyo_task(current);
 
 	/* register ourselves with the security framework */
 	security_add_hooks(tomoyo_hooks, ARRAY_SIZE(tomoyo_hooks), "tomoyo");
 	printk(KERN_INFO "TOMOYO Linux initialized\n");
-	blob = tomoyo_cred(cred);
-	*blob = &tomoyo_kernel_domain;
+	s->domain_info = &tomoyo_kernel_domain;
+	atomic_inc(&tomoyo_kernel_domain.users);
+	s->old_domain_info = NULL;
 	tomoyo_mm_init();
 
 	return 0;