rbd: avoid use-after-free in do_rbd_add() when rbd_dev_create() fails

In the Linux kernel, the following vulnerability has been resolved:

rbd: avoid use-after-free in do_rbd_add() when rbd_dev_create() fails

If getting an ID or setting up a work queue in rbd_dev_create() fails,

use-after-free on rbd_dev->rbd_client, rbd_dev->spec and rbd_dev->opts

is triggered in do_rbd_add(). The root cause is that the ownership of

these structures is transfered to rbd_dev prematurely and they all end

up getting freed when rbd_dev_create() calls rbd_dev_free() prior to

returning to do_rbd_add().

Found by Linux Verification Center (linuxtesting.org) with SVACE, an

incomplete patch submitted by Natalia Petrova <[email protected]>.