xfree86: ensure the readlink buffer is null-terminated

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Dave Airlie <airlied@redhat.com>

hw/xfree86/fbdevhw/fbdevhw.c

@@ -331,12 +331,12 @@ fbdev_open(int scrnIndex, const char *dev, char **namep)
 
     /* only touch non-PCI devices on this path */
     {
-        char buf[PATH_MAX];
+        char buf[PATH_MAX] = {0};
         char *sysfs_path = NULL;
         char *node = strrchr(dev, '/') + 1;
 
         if (asprintf(&sysfs_path, "/sys/class/graphics/%s", node) < 0 ||
-            readlink(sysfs_path, buf, sizeof(buf)) < 0 ||
+            readlink(sysfs_path, buf, sizeof(buf) - 1) < 0 ||
             strstr(buf, "devices/pci")) {
             free(sysfs_path);
             close(fd);