audit: keep inode pinned

Audit rules disappear when an inode they watch is evicted from the cache.
This is likely not what we want.

The guilty commit is "fsnotify: allow marks to not pin inodes in core",
which didn't take into account that audit_tree adds watches with a zero
mask.

Adding any mask should fix this.

Fixes: 90b1e7a57880 ("fsnotify: allow marks to not pin inodes in core")
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org # 2.6.36+
Signed-off-by: Paul Moore <pmoore@redhat.com>

kernel/audit_tree.c

@@ -154,6 +154,7 @@ static struct audit_chunk *alloc_chunk(int count)
 		chunk->owners[i].index = i;
 	}
 	fsnotify_init_mark(&chunk->mark, audit_tree_destroy_watch);
+	chunk->mark.mask = FS_IN_IGNORED;
 	return chunk;
 }