rbd: fix use-after free of rbd_dev->disk
rbd: fix use-after free of rbd_dev->disk

Removing a device deallocates the disk, unschedules the watch, and
finally cleans up the rbd_dev structure. rbd_dev_refresh(), called
from the watch callback, updates the disk size and rbd_dev
structure. With no locking between them, rbd_dev_refresh() may use the
device or rbd_dev after they've been freed.

To fix this, check whether RBD_DEV_FLAG_REMOVING is set before
updating the disk size in rbd_dev_refresh(). In order to prevent a
race where rbd_dev_refresh() is already revalidating the disk when
rbd_remove() is called, move the call to rbd_bus_del_dev() after the
watch is unregistered and all notifies are complete. It's safe to
defer deleting this structure because no new requests can be submitted
once the RBD_DEV_FLAG_REMOVING is set, since the device cannot be
opened.

Fixes: http://tracker.ceph.com/issues/5636
Signed-off-by: Josh Durgin <51652c783f70f5b272ebd02f1fd20d3af7a2449f@inktank.com>
Reviewed-by: Alex Elder <f429030cf5c0faf36fac3d102073b6e63a647baa@linaro.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs