[bug report] skd: Avoid that module unloading triggers a use-after-free

[Dan Carpenter]

Hello Bart Van Assche,

This is a semi-automatic email about new static checker warnings.

The patch 7277cc67b391: "skd: Avoid that module unloading triggers a 
use-after-free" from Aug 17, 2017, leads to the following Smatch 
complaint:

drivers/block/skd_main.c:3080 skd_free_disk()
         error: we previously assumed 'disk' could be null (see line 3074)

drivers/block/skd_main.c
  3073  
  3074          if (disk && (disk->flags & GENHD_FL_UP))
                    ^^^^
Existing code checked for NULL.  The new code shuffles things around.

  3075                  del_gendisk(disk);
  3076  
  3077          if (skdev->queue) {
  3078                  blk_cleanup_queue(skdev->queue);
  3079                  skdev->queue = NULL;
  3080                  disk->queue = NULL;
                        ^^^^^^^^^^^
Now we don't check here.

  3081          }
  3082  

regards,
dan carpenter