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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. Signed-off-by: Prasanna Kumar Kalever <prasanna.kalever@redhat.com> Reviewed-by: Xiubo Li <xiubli@redhat.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20210429102828.31248-1-prasanna.kalever@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.