staging: comedi: check return code of put_user

Function put_user may fail. Check for it.
Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/comedi/comedi_fops.c

@@ -537,7 +537,8 @@ static int do_chaninfo_ioctl(struct comedi_device *dev,
 
 			x = (dev->minor << 28) | (it.subdev << 24) | (i << 16) |
 			    (s->range_table_list[i]->length);
-			put_user(x, it.rangelist + i);
+			if (put_user(x, it.rangelist + i))
+				return -EFAULT;
 		}
 #if 0
 		if (copy_to_user(it.rangelist, s->range_type_list,