Reinforce the already stated policy that LANDLOCK_ACCESS_FS_TRUNCATE should
always go hand in hand with LANDLOCK_ACCESS_FS_WRITE_FILE, as their
meanings and enforcement overlap in counterintuitive ways.
On many common file systems, fallocate(2) offers a way to shorten files as
long as the file is opened for writing, side-stepping the
LANDLOCK_ACCESS_FS_TRUNCATE right.
Assisted-by: Gemini-CLI:gemini-3.1
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20260401150911.1038072-1-gnoack@google.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Add LANDLOCK_RESTRICT_SELF_TSYNC to the backwards compatibility example
for restrict flags. This introduces completeness, similar to that of
the ruleset attributes example. However, as the new example can impact
enforcement in certain cases, an appropriate warning is also included.
Additionally, I modified the two comments of the example to make them
more consistent with the ruleset attributes example's.
Signed-off-by: Panagiotis "Ivory" Vasilopoulos <git@n0toose.net>
Co-developed-by: Dan Cojocaru <dan@dcdev.ro>
Signed-off-by: Dan Cojocaru <dan@dcdev.ro>
Reviewed-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20260304-landlock-docs-add-tsync-example-v4-1-819a276f05c5@n0toose.net
[mic: Update date, improve comments consistency, fix newline issue]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Add errata section with code examples for querying errata and a warning
that most applications should not check errata. Use kernel-doc directives
to include errata descriptions from the header files instead of manual
links.
Also enhance existing DOC sections in security/landlock/errata/abi-*.h
files with Impact sections, and update the code comment in syscalls.c
to remind developers to update errata documentation when applicable.
This addresses the gap where the kernel implements errata tracking
but provides no user-facing documentation on how to use it, while
improving the existing technical documentation in-place rather than
duplicating it.
Signed-off-by: Samasth Norway Ananda <samasth.norway.ananda@oracle.com>
Reviewed-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20260128031814.2945394-3-samasth.norway.ananda@oracle.com
[mic: Cosmetic fix]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Add backwards compatibility handling for the restrict flags introduced
in ABI version 7. This is shown as a separate code block (similar to
the ruleset_attr handling in the switch statement) because restrict flags
are passed to landlock_restrict_self() rather than being part of the
ruleset attributes.
Also fix misleading description of the /usr rule which incorrectly
stated it "only allow[s] reading" when the code actually allows both
reading and executing (LANDLOCK_ACCESS_FS_EXECUTE is included in
allowed_access).
Signed-off-by: Samasth Norway Ananda <samasth.norway.ananda@oracle.com>
Reviewed-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20260128031814.2945394-2-samasth.norway.ananda@oracle.com
[mic: Rebased and fixed conflict]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
* Clarify terminology
* Stop mixing the unix(7) and signal(7) aspects in the explanation.
Terminology:
* The *IPC Scope* of a Landlock domain is that Landlock domain and its
nested domains.
* An *operation* (e.g., signaling, connecting to abstract UDS) is said to
be *scoped within a domain* when the flag for that operation was set at
ruleset creation time. This means that for the purpose of this
operation, only processes within the domain's IPC scope are reachable.
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20250303194510.135506-4-gnoack@google.com
[mic: Update doc date]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
* Fix some typos, incomplete or confusing phrases.
* Split paragraphs where appropriate.
* List the same error code multiple times,
if it has multiple possible causes.
* Bring wording closer to the man page wording,
which has undergone more thorough review
(esp. for LANDLOCK_ACCESS_FS_WRITE_FILE).
* Small semantic clarifications
* Call the ephemeral port range "ephemeral"
* Clarify reasons for EFAULT in landlock_add_rule()
* Clarify @rule_type doc for landlock_add_rule()
This is a collection of small fixes which I collected when preparing the
corresponding man pages [1].
Cc: Alejandro Colomar <alx@kernel.org>
Cc: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20240715155554.2791018-1-gnoack@google.com [1]
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20240715160328.2792835-2-gnoack@google.com
[mic: Add label to link, fix formatting spotted by make htmldocs,
synchronize userspace-api documentation's date]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Extend the kernel support section with one subsection for build time
configuration and another for boot time configuration.
Extend the boot time subsection with a concrete example.
Update the journalctl command to include the boot option.
Cc: Kees Cook <keescook@chromium.org>
Reviewed-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20240227110550.3702236-1-mic@digikod.net
[mic: Improve wording as suggested by Günther]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Allow mount point and root directory changes when there is no filesystem
rule tied to the current Landlock domain. This doesn't change anything
for now because a domain must have at least a (filesystem) rule, but
this will change when other rule types will come. For instance, a domain
only restricting the network should have no impact on filesystem
restrictions.
Add a new get_current_fs_domain() helper to quickly check filesystem
rule existence for all filesystem LSM hooks.
Remove unnecessary inlining.
Link: https://lore.kernel.org/r/20231026014751.414649-3-konstantin.meskhidze@huawei.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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>
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
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>
