On 4/29/21 4:28 AM, Prasanna Kumar Kalever wrote: > Problem: > On reconfigure of device, there is no way to defend if the backend > storage is matching with the initial backend storage. > > Say, if an initial connect request for backend "pool1/image1" got > mapped to /dev/nbd0 and the userspace process is terminated. A next > reconfigure request within NBD_ATTR_DEAD_CONN_TIMEOUT is allowed to > use /dev/nbd0 for a different backend "pool1/image2" > > For example, an operation like below could be dangerous: > > $ sudo rbd-nbd map --try-netlink rbd-pool/ext4-image > /dev/nbd0 > $ sudo blkid /dev/nbd0 > /dev/nbd0: UUID="bfc444b4-64b1-418f-8b36-6e0d170cfc04" TYPE="ext4" > $ sudo pkill -9 rbd-nbd > $ sudo rbd-nbd attach --try-netlink --device /dev/nbd0 rbd-pool/xfs-image > /dev/nbd0 > $ sudo blkid /dev/nbd0 > /dev/nbd0: UUID="d29bf343-6570-4069-a9ea-2fa156ced908" TYPE="xfs" > > Solution: > Provide a way for userspace processes to keep some metadata to identify > between the device and the backend, so that when a reconfigure request is > made, we can compare and avoid such dangerous operations. > > With this solution, as part of the initial connect request, backend > path can be stored in the sysfs per device config, so that on a reconfigure > request it's easy to check if the backend path matches with the initial > connect backend path. > > Please note, ioctl interface to nbd will not have these changes, as there > won't be any reconfigure. Applied, thanks. -- Jens Axboe
