Open map_files with O_PATH

This descriptor is stat()-ed and used to dump file information.
In both cases even read access is not required. Even if we decide
to go dump ghost file out of it we'll re-open one with O_RDONLY.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>

proc_parse.c

@@ -214,7 +214,7 @@ static int vma_get_mapfile(char *fname, struct vma_area *vma, DIR *mfd,
 	 * so later we might refer to it via /proc/self/fd/vm_file_fd
 	 * if needed.
 	 */
-	vma->vm_file_fd = openat(dirfd(mfd), path, O_RDONLY);
+	vma->vm_file_fd = openat(dirfd(mfd), path, O_PATH);
 	if (vma->vm_file_fd < 0) {
 		if (errno == ENOENT)
 			/* Just mapping w/o map_files link */