Re: [PATCH v2] nbd: fix uaf in nbd_open

[Christoph Hellwig <hch@lst.de>]

I don't think this is actually enough on it's own.  You'll also
need to move al the teardown logic that is currently in
nbd_dev_remove.  And with this you should be able to remove the
NULL check in nbd_open, and propably the nbd_index_mutex critical
section.  Although that'll need a very careful audit.