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* landlock: Document Landlock's file truncation supportGünther Noack2022-10-191-7/+60
| | | | | | | | | | | | | Use the LANDLOCK_ACCESS_FS_TRUNCATE flag in the tutorial. Adapt the backwards compatibility example and discussion to remove the truncation flag where needed. Point out potential surprising behaviour related to truncate. Signed-off-by: Günther Noack <gnoack3000@gmail.com> Link: https://lore.kernel.org/r/20221018182216.301684-12-gnoack3000@gmail.com Signed-off-by: Mickaël Salaün <mic@digikod.net>
* landlock: Fix documentation styleMickaël Salaün2022-09-291-12/+13
| | | | | | | | | | | It seems that all code should use double backquotes, which is also used to convert "%" defines. Let's use an homogeneous style and remove all use of simple backquotes (which should only be used for emphasis). Cc: Günther Noack <gnoack3000@gmail.com> Cc: Paul Moore <paul@paul-moore.com> Signed-off-by: Mickaël Salaün <mic@digikod.net> Link: https://lore.kernel.org/r/20220923154207.3311629-4-mic@digikod.net
* landlock: Slightly improve documentation and fix spellingMickaël Salaün2022-09-291-5/+5
| | | | | | | | | | | | | | | Now that we have more than one ABI version, make limitation explanation more consistent by replacing "ABI 1" with "ABI < 2". This also indicates which ABIs support such past limitation. Improve documentation consistency by not using contractions. Fix spelling in fs.c . Cc: Paul Moore <paul@paul-moore.com> Signed-off-by: Mickaël Salaün <mic@digikod.net> Reviewed-by: Günther Noack <gnoack3000@gmail.com> Link: https://lore.kernel.org/r/20220923154207.3311629-3-mic@digikod.net
* landlock: Explain how to support LandlockMickaël Salaün2022-05-231-1/+28
| | | | | | | | | | | Let's help users by documenting how to enable and check for Landlock in the kernel and the running system. The userspace-api section may not be the best place for this but it still makes sense to put all the user documentation at the same place. Signed-off-by: Mickaël Salaün <mic@digikod.net> Link: https://lore.kernel.org/r/20220513112743.156414-1-mic@digikod.net Reviewed-by: Paul Moore <paul@paul-moore.com>
* landlock: Document good practices about filesystem policiesMickaël Salaün2022-05-231-0/+21
| | | | | | | | | | Explain how to set access rights per hierarchy in an efficient and safe way, especially with the LANDLOCK_ACCESS_FS_REFER side effect (i.e. partial ordering and constraints for access rights per hierarchy). Reviewed-by: Paul Moore <paul@paul-moore.com> Signed-off-by: Mickaël Salaün <mic@digikod.net> Link: https://lore.kernel.org/r/20220506161102.525323-12-mic@digikod.net
* landlock: Document LANDLOCK_ACCESS_FS_REFER and ABI versioningMickaël Salaün2022-05-231-20/+106
| | | | | | | | | | | | | | | | | | Add LANDLOCK_ACCESS_FS_REFER in the example and properly check to only use it if the current kernel support it thanks to the Landlock ABI version. Move the file renaming and linking limitation to a new "Previous limitations" section. Improve documentation about the backward and forward compatibility, including the rational for ruleset's handled_access_fs. Update the document date. Reviewed-by: Paul Moore <paul@paul-moore.com> Signed-off-by: Mickaël Salaün <mic@digikod.net> Link: https://lore.kernel.org/r/20220506161102.525323-11-mic@digikod.net
* landlock: Reduce the maximum number of layers to 16Mickaël Salaün2022-05-231-2/+2
| | | | | | | | | | | | | | | | | | The maximum number of nested Landlock domains is currently 64. Because of the following fix and to help reduce the stack size, let's reduce it to 16. This seems large enough for a lot of use cases (e.g. sandboxed init service, spawning a sandboxed SSH service, in nested sandboxed containers). Reducing the number of nested domains may also help to discover misuse of Landlock (e.g. creating a domain per rule). Add and use a dedicated layer_mask_t typedef to fit with the number of layers. This might be useful when changing it and to keep it consistent with the maximum number of layers. Reviewed-by: Paul Moore <paul@paul-moore.com> Link: https://lore.kernel.org/r/20220506161102.525323-3-mic@digikod.net Cc: stable@vger.kernel.org Signed-off-by: Mickaël Salaün <mic@digikod.net>
* docs: userspace-api: landlock.rst: avoid using ReST :doc:`foo` markupMauro Carvalho Chehab2021-06-171-5/+6
| | | | | | | | | The :doc:`foo` tag is auto-generated via automarkup.py. So, use the filename at the sources, instead of :doc:`foo`. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Link: https://lore.kernel.org/r/24888a9c5da3c505b2bc274fcd83be348dbaf972.1623824363.git.mchehab+huawei@kernel.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
* landlock: Add user and kernel documentationMickaël Salaün2021-04-221-0/+311
Add a first document describing userspace API: how to define and enforce a Landlock security policy. This is explained with a simple example. The Landlock system calls are described with their expected behavior and current limitations. Another document is dedicated to kernel developers, describing guiding principles and some important kernel structures. This documentation can be built with the Sphinx framework. Cc: James Morris <jmorris@namei.org> Cc: Jann Horn <jannh@google.com> Cc: Serge E. Hallyn <serge@hallyn.com> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> Reviewed-by: Vincent Dagonneau <vincent.dagonneau@ssi.gouv.fr> Reviewed-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20210422154123.13086-13-mic@digikod.net Signed-off-by: James Morris <jamorris@linux.microsoft.com>