Smack: Test if smack is enabled before mounting

Since on most systems with xattr systemd will compile with Smack
support enabled, we still attempt to mount various fs's with
Smack-only options.

Before mounting any of these Smack-related filesystems with
Smack specific mount options, check if Smack is functionally
active on the running kernel.

If Smack is really enabled in the kernel, all these Smack mounts
are now *fatal*, as they should be.

We no longer mount smackfs if systemd was compiled without
Smack support. This makes it easier to make smackfs mount
failures a critical error when Smack is enabled.

We no longer mount these filesystems with their Smack specific
options inside containers. There these filesystems will be
mounted with there non-mount smack options for now.

1 files changed, 36 insertions, 0 deletions

diff --git a/src/shared/smack-util.c b/src/shared/smack-util.c
new file mode 100644
index 0000000000..a73eaac6de
--- /dev/null
+++ b/src/shared/smack-util.c
@@ -0,0 +1,36 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2013 Intel Corporation
+
+  Author: Auke Kok <auke-jan.h.kok@intel.com>
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "smack-util.h"
+
+#include <unistd.h>
+
+static int use_smack_cached = -1;
+
+bool use_smack(void) {
+
+        if (use_smack_cached < 0)
+                use_smack_cached = (access("/sys/fs/smackfs", F_OK) >= 0);
+
+        return use_smack_cached;
+}