--- libdrm-2.4.74/xf86drm.c	2016-11-29 20:15:10.000000000 +0900
+++ new/xf86drm.c	2016-12-10 16:42:04.273571879 +0900
@@ -2874,11 +2874,12 @@
     if (fd < 0)
         return -errno;
 
-    ret = read(fd, data, sizeof(data));
-    data[sizeof(data)-1] = '\0';
+    ret = read(fd, data, sizeof(data)-1);
     close(fd);
     if (ret < 0)
         return -errno;
+    data[ret] = '\0';
+    
 
 #define TAG "PCI_SLOT_NAME="
     str = strstr(data, TAG);