staging: lustre: libcfs: test if data is NULL

Make sure data is not NULL otherwise we get an oops
when using the IOC_LIBCFS_MARK_DEBUG ioctl.
Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5435
Reviewed-on: http://review.whamcloud.com/11313Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lnet/libcfs/module.c

@@ -150,7 +150,7 @@ static int libcfs_ioctl(struct cfs_psdev_file *pfile, unsigned long cmd,
 	 * Handled in arch/cfs_module.c
 	 */
 	case IOC_LIBCFS_MARK_DEBUG:
-		if (!data->ioc_inlbuf1 ||
+		if (!data || !data->ioc_inlbuf1 ||
 		    data->ioc_inlbuf1[data->ioc_inllen1 - 1] != '\0') {
 			err = -EINVAL;
 			goto out;