staging: lustre: libcfs: test if userland data is to small

Ensure that user land data is at least the smallest size.
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/linux/linux-module.c

@@ -73,6 +73,11 @@ int libcfs_ioctl_getdata(struct libcfs_ioctl_hdr **hdr_pp,
 		return -EINVAL;
 	}
 
+	if (hdr.ioc_len < sizeof(struct libcfs_ioctl_data)) {
+		CERROR("libcfs ioctl: user buffer too small for ioctl\n");
+		return -EINVAL;
+	}
+
 	if (hdr.ioc_len > LIBCFS_IOC_DATA_MAX) {
 		CERROR("libcfs ioctl: user buffer is too large %d/%d\n",
 		       hdr.ioc_len, LIBCFS_IOC_DATA_MAX);