audit: loginuid functions coding style

This is just a code rework.  It makes things more readable.  It does not
make any functional changes.

It does change the log messages to include both the old session id as
well the new and it includes a new res field, which means we get
messages even when the user did not have permission to change the
loginuid.
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>

kernel/auditsc.c

@@ -1966,6 +1966,39 @@ int auditsc_get_stamp(struct audit_context *ctx,
 /* global counter which is incremented every time something logs in */
 static atomic_t session_id = ATOMIC_INIT(0);
 
+static int audit_set_loginuid_perm(kuid_t loginuid)
+{
+#ifdef CONFIG_AUDIT_LOGINUID_IMMUTABLE
+	/* if we are unset, we don't need privs */
+	if (!audit_loginuid_set(current))
+		return 0;
+#else	/* CONFIG_AUDIT_LOGINUID_IMMUTABLE */
+	if (capable(CAP_AUDIT_CONTROL))
+		return 0;
+#endif /* CONFIG_AUDIT_LOGINUID_IMMUTABLE */
+	return -EPERM;
+}
+
+static void audit_log_set_loginuid(kuid_t koldloginuid, kuid_t kloginuid,
+				   unsigned int oldsessionid, unsigned int sessionid,
+				   int rc)
+{
+	struct audit_buffer *ab;
+	uid_t uid, ologinuid, nloginuid;
+
+	uid = from_kuid(&init_user_ns, task_uid(current));
+	ologinuid = from_kuid(&init_user_ns, koldloginuid);
+	nloginuid = from_kuid(&init_user_ns, kloginuid),
+
+	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_LOGIN);
+	if (!ab)
+		return;
+	audit_log_format(ab, "pid=%d uid=%u old auid=%u new auid=%u old "
+			 "ses=%u new ses=%u res=%d", current->pid, uid, ologinuid,
+			 nloginuid, oldsessionid, sessionid, !rc);
+	audit_log_end(ab);
+}
+
 /**
  * audit_set_loginuid - set current task's audit_context loginuid
  * @loginuid: loginuid value
@@ -1977,37 +2010,24 @@ static atomic_t session_id = ATOMIC_INIT(0);
 int audit_set_loginuid(kuid_t loginuid)
 {
 	struct task_struct *task = current;
-	struct audit_context *context = task->audit_context;
-	unsigned int sessionid;
+	unsigned int sessionid = -1;
+	kuid_t oldloginuid, oldsessionid;
+	int rc;
 
-#ifdef CONFIG_AUDIT_LOGINUID_IMMUTABLE
-	if (audit_loginuid_set(task))
-		return -EPERM;
-#else /* CONFIG_AUDIT_LOGINUID_IMMUTABLE */
-	if (!capable(CAP_AUDIT_CONTROL))
-		return -EPERM;
-#endif  /* CONFIG_AUDIT_LOGINUID_IMMUTABLE */
+	oldloginuid = audit_get_loginuid(current);
+	oldsessionid = audit_get_sessionid(current);
+
+	rc = audit_set_loginuid_perm(loginuid);
+	if (rc)
+		goto out;
 
 	sessionid = atomic_inc_return(&session_id);
-	if (context && context->in_syscall) {
-		struct audit_buffer *ab;
 
-		ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_LOGIN);
-		if (ab) {
-			audit_log_format(ab, "login pid=%d uid=%u "
-				"old auid=%u new auid=%u"
-				" old ses=%u new ses=%u",
-				task->pid,
-				from_kuid(&init_user_ns, task_uid(task)),
-				from_kuid(&init_user_ns, task->loginuid),
-				from_kuid(&init_user_ns, loginuid),
-				task->sessionid, sessionid);
-			audit_log_end(ab);
-		}
-	}
 	task->sessionid = sessionid;
 	task->loginuid = loginuid;
-	return 0;
+out:
+	audit_log_set_loginuid(oldloginuid, loginuid, oldsessionid, sessionid, rc);
+	return rc;
 }
 
 /**