(namespace) ipc/mqueue: The mqueue filesystem should never contain executables

BugLink: http://bugs.launchpad.net/bugs/1588056

Set SB_I_NOEXEC on mqueuefs to ensure small implementation mistakes
do not result in executable on mqueuefs by accident.
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
(backported from linux-next commit 3ee69014)
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

ipc/mqueue.c

@@ -307,6 +307,7 @@ static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
 	struct inode *inode;
 	struct ipc_namespace *ns = sb->s_fs_info;
 
+	sb->s_iflags |= SB_I_NOEXEC;
 	sb->s_blocksize = PAGE_CACHE_SIZE;
 	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
 	sb->s_magic = MQUEUE_MAGIC;