Add the first Landlock tracepoints, for ruleset lifecycle:
landlock_create_ruleset fires from the landlock_create_ruleset() syscall
handler, and landlock_free_ruleset fires in free_ruleset() before the
ruleset is freed.

These tracepoints, and the ones added by the following commits, share a
common design.  Rather than one polymorphic event distinguished by a
status field (as audit uses a shared record type with a "status="
field), each lifecycle transition and denial type gets its own event
with a type-safe TP_PROTO, giving precise ftrace filtering by event name
and type-safe eBPF access.  TP_PROTO passes the object pointer and the
fields are read from it in TP_fast_assign, so an eBPF program reads the
full object state (rules, access masks, hierarchy) via BTF from a single
pointer rather than from the flattened TP_STRUCT__entry fields.  The
whole cost is paid only when a tracer is attached; the static branch is
not taken otherwise.  Trace fields carry the bare access-right and scope
names (read_file), reusing the audit name tables; audit prepends the
category (fs.read_file), which the trace event name already conveys.
The trace header's DOC comment documents the consistency and locking
guarantees these events share.

create_ruleset needs no lock because the ruleset is not yet shared (its
file descriptor is not yet installed).  The deallocation events use the
"free_" prefix, not "drop_", because they fire when the object is
actually freed.

Add trace.c, built for CONFIG_TRACEPOINTS, which defines
CREATE_TRACE_POINTS, and extend CONFIG_SECURITY_LANDLOCK_LOG to also be
selected by CONFIG_TRACEPOINTS so the common log framework is available
to a tracepoints-only build.

Add an id field to struct landlock_ruleset, gated on CONFIG_TRACEPOINTS
and assigned from landlock_get_id_range() at creation.  Only the
tracepoints consume it (audit identifies domains, not rulesets), so it
does not exist in an audit-only build.  The Landlock ID is a stable u64
that names the ruleset across the trace stream and uses the same scheme
as audit, so a ruleset can be correlated between trace and audit
records.

Cc: Günther Noack <gnoack@google.com>
Cc: Justin Suess <utilityemal77@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tingmao Wang <m@maowtm.org>
Link: https://patch.msgid.link/20260811094338.288094-8-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Tracepoint emission requires the denial framework (layer identification,
request validation) without depending on CONFIG_AUDIT.  Separate the
denial logging infrastructure from the audit-specific code by
introducing a common log framework.

Create CONFIG_SECURITY_LANDLOCK_LOG, enabled by default when
CONFIG_AUDIT is set; a following commit extends it to CONFIG_TRACEPOINTS
when the first tracepoint consumer is added.  Move the common framework
(the request types, the layer identification and request validation, and
the landlock_log_denial() and landlock_log_free_domain() entry points)
into log.c and log.h, and keep the audit-specific record formatting in
audit.c. log.o is built for CONFIG_SECURITY_LANDLOCK_LOG and audit.o for
CONFIG_AUDIT, so the common framework is available to a tracepoints-only
build.  The entry points dispatch to no-op static inline audit stubs
without CONFIG_AUDIT, so the call sites stay unconditional.  Rename the
former landlock_log_drop_domain() to landlock_log_free_domain() to match
the landlock_free_domain tracepoint added in a following commit.

landlock_log_denial() counts denials even without audit, so its
declaration and no-op stub are guarded by CONFIG_SECURITY_LANDLOCK_LOG,
not CONFIG_AUDIT; a CONFIG_AUDIT guard would expose the stub and clash
with log.c's definition in a tracepoints-only build.

Widen the ID allocation (id.o and the landlock_init_id() /
landlock_get_id_range() declarations) and the log-state representation
(the domain_exec and log_subdomains_off credential fields, the
landlock_hierarchy log fields, and the code that maintains them) from
CONFIG_AUDIT to CONFIG_SECURITY_LANDLOCK_LOG, so each field and its
writer share one guard and are available to tracing without audit
support.

Widen the denial-path state that feeds the per-denial logging decision
the same way, so the "logged" verdict is computed identically whether or
not CONFIG_AUDIT is set.  Widening fown_layer is what keeps the
file-owner-signal path valid without audit: otherwise
hook_file_send_sigiotask() would leave layer_plus_one at zero, tripping
the is_valid_request() canary and dropping the LANDLOCK_SCOPE_SIGNAL
denial from tracing.

The ruleset-level quiet_masks stays on no CONFIG guard: it is builder
state validated and stored from user input, kept available so
LANDLOCK_ADD_RULE_QUIET flags are accepted and ignored, not rejected,
when CONFIG_SECURITY_LANDLOCK_LOG is disabled.

Cc: Günther Noack <gnoack@google.com>
Link: https://patch.msgid.link/20260811094338.288094-5-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Rulesets and domains serve fundamentally different purposes: a ruleset
is mutable and user-facing, created by landlock_create_ruleset(), while
a domain is immutable after construction and enforced on tasks via
landlock_restrict_self().  Today both are represented by struct
landlock_ruleset, which conflates mutable and immutable state in a
single type: the lock field is unused by domains, the hierarchy field is
unused by rulesets, and lifecycle functions must handle both cases.

Prepare for a clean type split by introducing two new structures:

- struct landlock_rules: the red-black tree roots and rule count, shared
  by both rulesets and domains.  Decoupling rule storage from the domain
  API lets the backing data structure change independently (e.g. to a
  hash table, cf. [1]).
- struct landlock_domain: the immutable domain enforced on tasks, with
  no lock field because its rules and access masks are fixed once
  construction completes.  The name reflects the role, not the internal
  data structure.

Add the domain lifecycle helpers (landlock_get_domain(),
landlock_put_domain(), landlock_put_domain_deferred()) and move domain.o
from landlock-$(CONFIG_AUDIT) to landlock-y, because these are needed
unconditionally, not just for audit logging.

No behavioral change.  The new types and lifecycle functions are not yet
used by any caller.

Cc: Günther Noack <gnoack@google.com>
Link: https://patch.msgid.link/20250523165741.693976-1-mic@digikod.net [1]
Link: https://patch.msgid.link/20260811094338.288094-2-mic@digikod.net
Reviewed-by: Tingmao Wang <m@maowtm.org>
[mic: Update copyright]
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Introduce the LANDLOCK_RESTRICT_SELF_TSYNC flag.  With this flag, a
given Landlock ruleset is applied to all threads of the calling
process, instead of only the current one.

Without this flag, multithreaded userspace programs currently resort
to using the nptl(7)/libpsx hack for multithreaded policy enforcement,
which is also used by libcap and for setuid(2).  Using this
userspace-based scheme, the threads of a process enforce the same
Landlock policy, but the resulting Landlock domains are still
separate.  The domains being separate causes multiple problems:

* When using Landlock's "scoped" access rights, the domain identity is
  used to determine whether an operation is permitted.  As a result,
  when using LANLDOCK_SCOPE_SIGNAL, signaling between sibling threads
  stops working.  This is a problem for programming languages and
  frameworks which are inherently multithreaded (e.g. Go).

* In audit logging, the domains of separate threads in a process will
  get logged with different domain IDs, even when they are based on
  the same ruleset FD, which might confuse users.

Cc: Andrew G. Morgan <morgan@kernel.org>
Cc: John Johansen <john.johansen@canonical.com>
Cc: Paul Moore <paul@paul-moore.com>
Suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20251127115136.3064948-2-gnoack@google.com
[mic: Fix restrict_self_flags test, clean up Makefile, allign comments,
reduce local variable scope, add missing includes]
Closes: https://github.com/landlock-lsm/linux/issues/2
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Add a new AUDIT_LANDLOCK_ACCESS record type dedicated to an access
request denied by a Landlock domain.  AUDIT_LANDLOCK_ACCESS indicates
that something unexpected happened.

For now, only denied access are logged, which means that any
AUDIT_LANDLOCK_ACCESS record is always followed by a SYSCALL record with
"success=no".  However, log parsers should check this syscall property
because this is the only sign that a request was denied.  Indeed, we
could have "success=yes" if Landlock would support a "permissive" mode.
We could also add a new field to AUDIT_LANDLOCK_DOMAIN for this mode
(see following commit).

By default, the only logged access requests are those coming from the
same executed program that enforced the Landlock restriction on itself.
In other words, no audit record are created for a task after it called
execve(2).  This is required to avoid log spam because programs may only
be aware of their own restrictions, but not the inherited ones.

Following commits will allow to conditionally generate
AUDIT_LANDLOCK_ACCESS records according to dedicated
landlock_restrict_self(2)'s flags.

The AUDIT_LANDLOCK_ACCESS message contains:
- the "domain" ID restricting the action on an object,
- the "blockers" that are missing to allow the requested access,
- a set of fields identifying the related object (e.g. task identified
  with "opid" and "ocomm").

The blockers are implicit restrictions (e.g. ptrace), or explicit access
rights (e.g. filesystem), or explicit scopes (e.g. signal).  This field
contains a list of at least one element, each separated with a comma.

The initial blocker is "ptrace", which describe all implicit Landlock
restrictions related to ptrace (e.g. deny tracing of tasks outside a
sandbox).

Add audit support to ptrace_access_check and ptrace_traceme hooks.  For
the ptrace_access_check case, we log the current/parent domain and the
child task.  For the ptrace_traceme case, we log the parent domain and
the current/child task.  Indeed, the requester and the target are the
current task, but the action would be performed by the parent task.

Audit event sample:

  type=LANDLOCK_ACCESS msg=audit(1729738800.349:44): domain=195ba459b blockers=ptrace opid=1 ocomm="systemd"
  type=SYSCALL msg=audit(1729738800.349:44): arch=c000003e syscall=101 success=no [...] pid=300 auid=0

A following commit adds user documentation.

Add KUnit tests to check reading of domain ID relative to layer level.

The quick return for non-landlocked tasks is moved from task_ptrace() to
each LSM hooks.

It is not useful to inline the audit_enabled check because other
computation are performed by landlock_log_denial().

Use scoped guards for RCU read-side critical sections.

Cc: Günther Noack <gnoack@google.com>
Acked-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20250320190717.2287696-10-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Landlock IDs can be generated to uniquely identify Landlock objects.
For now, only Landlock domains get an ID at creation time.  These IDs
map to immutable domain hierarchies.

Landlock IDs have important properties:
- They are unique during the lifetime of the running system thanks to
  the 64-bit values: at worse, 2^60 - 2*2^32 useful IDs.
- They are always greater than 2^32 and must then be stored in 64-bit
  integer types.
- The initial ID (at boot time) is randomly picked between 2^32 and
  2^33, which limits collisions in logs across different boots.
- IDs are sequential, which enables users to order them.
- IDs may not be consecutive but increase with a random 2^4 step, which
  limits side channels.

Such IDs can be exposed to unprivileged processes, even if it is not the
case with this audit patch series.  The domain IDs will be useful for
user space to identify sandboxes and get their properties.

These Landlock IDs are more secure that other absolute kernel IDs such
as pipe's inodes which rely on a shared global counter.

For checkpoint/restore features (i.e. CRIU), we could easily implement a
privileged interface (e.g. sysfs) to set the next ID counter.

IDR/IDA are not used because we only need a bijection from Landlock
objects to Landlock IDs, and we must not recycle IDs.  This enables us
to identify all Landlock objects during the lifetime of the system (e.g.
in logs), but not to access an object from an ID nor know if an ID is
assigned.   Using a counter is simpler, it scales (i.e. avoids growing
memory footprint), and it does not require locking.  We'll use proper
file descriptors (with IDs used as inode numbers) to access Landlock
objects.

Cc: Günther Noack <gnoack@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20250320190717.2287696-3-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>

ptrace.[ch] are currently only used for the ptrace LSM hooks but their
scope will expand with IPCs and audit support.  Rename ptrace.[ch] to
task.[ch], which better reflect their content.  Similarly, rename
landlock_add_ptrace_hooks() to landlock_add_task_hooks().  Keep header
files for now.

Cc: Günther Noack <gnoack@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20240307093923.1466071-2-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Add network rules support in the ruleset management helpers and the
landlock_create_ruleset() syscall. Extend user space API to support
network actions:
* Add new network access rights: LANDLOCK_ACCESS_NET_BIND_TCP and
  LANDLOCK_ACCESS_NET_CONNECT_TCP.
* Add a new network rule type: LANDLOCK_RULE_NET_PORT tied to struct
  landlock_net_port_attr. The allowed_access field contains the network
  access rights, and the port field contains the port value according to
  the controlled protocol. This field can take up to a 64-bit value
  but the maximum value depends on the related protocol (e.g. 16-bit
  value for TCP). Network port is in host endianness [1].
* Add a new handled_access_net field to struct landlock_ruleset_attr
  that contains network access rights.
* Increment the Landlock ABI version to 4.

Implement socket_bind() and socket_connect() LSM hooks, which enable
to control TCP socket binding and connection to specific ports.

Expand access_masks_t from u16 to u32 to be able to store network access
rights alongside filesystem access rights for rulesets' handled access
rights.

Access rights are not tied to socket file descriptors but checked at
bind() or connect() call time against the caller's Landlock domain. For
the filesystem, a file descriptor is a direct access to a file/data.
However, for network sockets, we cannot identify for which data or peer
a newly created socket will give access to. Indeed, we need to wait for
a connect or bind request to identify the use case for this socket.
Likewise a directory file descriptor may enable to open another file
(i.e. a new data item), but this opening is also restricted by the
caller's domain, not the file descriptor's access rights [2].

[1] https://lore.kernel.org/r/278ab07f-7583-a4e0-3d37-1bacd091531d@digikod.net
[2] https://lore.kernel.org/r/263c1eb3-602f-57fe-8450-3f138581bee7@digikod.net

Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20231026014751.414649-9-konstantin.meskhidze@huawei.com
[mic: Extend commit message, fix typo in comments, and specify
endianness in the documentation]
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>

These 3 system calls are designed to be used by unprivileged processes
to sandbox themselves:
* landlock_create_ruleset(2): Creates a ruleset and returns its file
  descriptor.
* landlock_add_rule(2): Adds a rule (e.g. file hierarchy access) to a
  ruleset, identified by the dedicated file descriptor.
* landlock_restrict_self(2): Enforces a ruleset on the calling thread
  and its future children (similar to seccomp).  This syscall has the
  same usage restrictions as seccomp(2): the caller must have the
  no_new_privs attribute set or have CAP_SYS_ADMIN in the current user
  namespace.

All these syscalls have a "flags" argument (not currently used) to
enable extensibility.

Here are the motivations for these new syscalls:
* A sandboxed process may not have access to file systems, including
  /dev, /sys or /proc, but it should still be able to add more
  restrictions to itself.
* Neither prctl(2) nor seccomp(2) (which was used in a previous version)
  fit well with the current definition of a Landlock security policy.

All passed structs (attributes) are checked at build time to ensure that
they don't contain holes and that they are aligned the same way for each
architecture.

See the user and kernel documentation for more details (provided by a
following commit):
* Documentation/userspace-api/landlock.rst
* Documentation/security/landlock.rst

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: James Morris <jmorris@namei.org>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Link: https://lore.kernel.org/r/20210422154123.13086-9-mic@digikod.net
Signed-off-by: James Morris <jamorris@linux.microsoft.com>

Using Landlock objects and ruleset, it is possible to tag inodes
according to a process's domain.  To enable an unprivileged process to
express a file hierarchy, it first needs to open a directory (or a file)
and pass this file descriptor to the kernel through
landlock_add_rule(2).  When checking if a file access request is
allowed, we walk from the requested dentry to the real root, following
the different mount layers.  The access to each "tagged" inodes are
collected according to their rule layer level, and ANDed to create
access to the requested file hierarchy.  This makes possible to identify
a lot of files without tagging every inodes nor modifying the
filesystem, while still following the view and understanding the user
has from the filesystem.

Add a new ARCH_EPHEMERAL_INODES for UML because it currently does not
keep the same struct inodes for the same inodes whereas these inodes are
in use.

This commit adds a minimal set of supported filesystem access-control
which doesn't enable to restrict all file-related actions.  This is the
result of multiple discussions to minimize the code of Landlock to ease
review.  Thanks to the Landlock design, extending this access-control
without breaking user space will not be a problem.  Moreover, seccomp
filters can be used to restrict the use of syscall families which may
not be currently handled by Landlock.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jann Horn <jannh@google.com>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Serge E. Hallyn <serge@hallyn.com>
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Link: https://lore.kernel.org/r/20210422154123.13086-8-mic@digikod.net
Signed-off-by: James Morris <jamorris@linux.microsoft.com>